General Keys to Families and Special Groups

Please try our next iteration of the Michigan Flora Online here.

The new site offers several benefits over the existing website, including real coordinate mapping, giving a clearer view of the density of documentation as well as more precision about plant distributions and their link to landforms. We will also have the ability to update species pages more regularly, both in terms of new collections and as more existing Michigan specimens are georeferenced. In addition, we have a better photo display, and offer indented keys.

FERN FAMILY KEY - Ferns and other spore-bearing vascular plants (“fern allies”); plants bearing spores and lacking flowers and seeds.

SEED PLANT FAMILY KEY - Seed plants (conifers and flowering plants); plants with seeds, born either in cones or in ovaries formed in flowers.

This series of keys is intended to lead one to the family, or sometimes directly to the genus or species, of an unknown plant. Therefore, the keys are based on the most reliable and easily observed characters for that purpose; only rarely (and incidentally) do they reflect the natural relationships and classification of the families. Diverse families (or their component genera and species) will usually key down at more than one place, so the keys often cannot be “worked backwards” to gain a concise description of the diagnostic features of a family.

Furthermore, the keys accommodate a number of easy misinterpretations that a beginner might make (e.g., considering the 3 bracts of Hepatica to be sepals; or believing a series of perianth parts to be absent when in fact the calyx or corolla is present but either very tiny or very early deciduous; or interpreting a very deeply lobed corolla as composed of separate petals). And they accommodate some ambiguities on the part of the plants themselves (e.g., if the ovary is only partly inferior, it should key under both “superior” and “inferior”; or if the perianth is only slightly bilaterally symmetrical it should key also under “regular”). However, plant taxa are composed of living organisms, and hence are variable; there will always be some individuals so “far out” as to defy identification by any key. Keys are a tool to help you learn the plants, not a subsitute for knowing them.

The keys are designed to cover only seed-plants known from Michigan and may not work for other species in the same families or genera. Except for a few true aquatic species in key A, ferns and their “allies” (horsetails, clubmosses, etc.) are in a separate key. Ordinarily, flowers are required for use of the seed-plant keys; the diversity of plants covered simply does not allow a key based on vegetative characters alone. Many aquatic plants are, however, seen but rarely in flower and even then the flowers are often much reduced and obscure; but they can be identified vegetatively. Therefore, many of these plants are disposed of in Key A, the first of the individual keys.

The summary of characters at the beginning of each individual key is not always exhaustive; e.g., plants which will key as aquatics (Key A) or with neither green color nor developed leaves (Key C) may not run under later keys even though the later summary headings do not explicitly exclude such plants. Nevertheless, before forging ahead in any of the individual keys, the user should find it helpful to read the summary, as a reminder of how one arrived there and as an opportunity to confirm accurate reading thus far.

Unless explicitly stated to the contrary, references to “flowers” are to normal open flowers (showy or obscure) and not to cleistogamous flowers (fertilized and setting seed while remaining in “bud”). As always, keys should be read carefully. For instance, if the perianth (sepals and/or petals) is said to be regular (radially symmetrical), that does not necessarily mean that the reproductive parts (stamens and/or pistils) are also regular.



1. Leaves less than 1 cm long, sometimes scale-like, usually numerous and closely spaced along the stem (in separate whorls in Equisetaceae)

2. Leaves scale-like, blackish or brown, with whitish margins, in separated whorls of 3–30; stems jointed, hollow


2. Leaves green, not scale-like, alternate or opposite; stems solid

3. Plants free floating on water; tiny (duckweed sized)


3. Plants terrestrial, rooted in soil or occasionally on rocks

4. Plants resembling a moss (almost 2-dimensional) or new growth of a Juniper or a miniature clubmoss. Spores (of two sizes) hidden beneath the expanded parts of green leaves (sporophylls) in fertile stems that are often the only erect part of the plant


4. Plants always 3-dimensional, resembling large mosses, miniature spruce/fir trees or the ultimate branches of Thuja (white cedar). Spores in discrete bean-shaped sporangia in leaf axils or in strobili subtended by usually non-green bract-like sporophylls


1. Leaves more than 1 cm long (often much longer), solitary or relatively few in number (except in the aquatic Isoetes); if more numerous, then borne singly and more or less spaced out along a rhizome, or forming a crown or tuft

5. Leaves ± round in cross section composed of 4 hollow tubes (seen in cross section), quill-like, rather abruptly expanded at base to enclose sporangia


5. Leaves with a flat blade, not quill-like with 4 hollow tubes, not expanded at the very base to contain a sporangium

6. Photosynthetic blades 4-parted in clover-like fashion, often floating on water


6. Photosynthetic blades not divided or clover-like, not floating on water

7. Sporangia fused laterally into 2-rowed, long-stalked spike-like structure (synangium) and opening by double rows of pores or slits, this borne on a stalk separate from the sterile blade; vegetative part of leaf entire

OPHIOGLOSSACEAE(in part, Ophioglossum)

7. Sporangia not fused into synangia, separate from the sterile blade or not; sterile parts of leaves usually variously divided (if not, then bearing elongated sori)

8. Leaves with rachis twining, high-climbing, pinna midribs evidently forked


8. Leaves not twining nor (normally) with forked pinna midribs, the frond usually pinnate, palmate or undivided

9. Spores in globose sporangia 0.5–1 mm in diameter, opening without an annulus (band of specialized cells) and containing hundreds to thousands of spores; indusia absent; borne singly on special fertile branches that turn yellow and eventually shrivel at or before spore release [do not mistake the fertile fronds of the Onocleaceae, with hard, rolled up pinnae containing many tiny sporangia for these larger globose sporangial structures]

10. Leaves usually single per plant, often less than 30 cm tall; fertile portions of leaves (normally long-stalked) inserted near base of sterile portion; spores whitish or yellow, thousands per sporangium


10. Leaves several to many per plant, borne in a cluster, normally more than 30 cm long; fertile portion of leaves apical, in center of a leaf, or leaves dimorphic with sporangia on separate fertile leaves; spores green, hundreds per sporangium


9. Spores in sporangia (excluding stalks) less than 0.4 mm, usually containing 16–64 spores, opening with an annulus; indusia present or absent; sporangia borne in round or elongated clusters (sori) borne on the undersides or along the margins of  regular, green blades or sometimes inside hard, inrolled leaf tissue on separate non-green but hard and persistent fertile fronds

11. Sori borne inside hard, inrolled pinnae segments in separate stiff, sharply differentiated fertile leaves that dry hard and brown upon spore release and are long persistent


11. Sori borne on regular green leaves, these sometimes somewhat different in form from the vegetative leaves, but not becoming hard, brown, and persistent

12. Sori elongate, arranged end to end in one row on each side of the midrib of pinnatifid or pinnate blades to form a chain; species of acid bogs and adjacent open swamps with long creeping rhizomes bearing well separated leaves


12. Sori round to elongate, but not arranged end to end to form a chain on either side of the midrib; leaf blades, rhizomes, and habitat various (but plants usually not in acid bogs)

13. Stems and petiole bases bearing only hairs one cell wide, lacking scales (two cells or more wide); sori marginal or nearly so; indusia cuplike and attached proximally and sometimes along sides, or formed by revolute blade margins


13. Stems and petiole bases bearing at least some scales several cells wide; sori marginal or not; indusia linear, reniform, peltate, hood-like, or absent, sometimes replaced by false indusium formed by reflexed, recurved or revolute blade margins

14. Sori elongated and distinct, occurring at the leaf margin, and concealed by folded flaps of blade tissue or forming a ± continuous marginal band and concealed by revolute blade margins


14. Sori elongated or round, but not arrayed along the leaf margin nor concealed by flaps of blade tissue

15. Sori elongated; indusia elongate and attached on one side to form a flap

16. Leaves ± firm, evergreen; plants usually less than 30 cm tall and often of rocky habitats in shade or sun (open young woods and fields in one species)


16. Leaves thin-textured, deciduous; plants often more than 30 cm tall and usually of forest understories, occasionally in more open habitats

17. Pinnae lobed or divided, as well as sometimes finely toothed


17. Pinnae finely toothed, but otherwise undivided


15. Sori round; indusia attached at a point, borne under the sori, hood-like, or absent

18. Indusia absent and blades deeply pinnately lobed or once pinnate with sparsely denticulate segments; sori ca. 1.2–2.5 mm wide 


18. Indusia present or sometimes absent but blades pinnate with deeply divided segments to tripinnate; sori ca. 0.3–1.8 mm wide

19. Indusia completely surrounding sori, attached beneath the sorus and forming a ring of filaments or narrow scales arching over the it; small (to ca. 25 cm) ferns mostly of cliffs and cliff ledges


19. Indusia attached centrally or laterally, but not surrounding sorus in a cup-like fashion, membranous, not composed of filaments or scales; plant sizes and habitats various

20. Blades ternate (divided into 3 more or less equal parts); indusium lacking

CYSTOPTERIDACEAE (in part, Gymnocarpium)

20. Blades pinnate; indusium present (except in Phegopteris)

21. Leaf margins ciliate with whitish hairs; plants colonial from long-creeping rhizomes (fronds spaced 5–40 mm or more apart on the rhizome)


21. Leaf margins lacking whitish cilia (may have bristle-tipped teeth or the blade surface may have brownish hairs); plants solitary from essentially erect rhizomes or forming clumps or patches from short-creeping rhizomes (fronds separated by less than ca. 5 mm), except in Cystopteris protrusa

22. Blade margins (especially at the apex of the pinnules) with teeth sharply acute, acuminate, or contracted to a bristle-like tip (except in D. fragrans and D. marginalis); fronds firm, long persistent into the fall or even evergreen; indusia peltate or attached laterally at one point, ± persistent


22. Blade margins with blunt teeth; fronds delicate, arising early in the season and often deciduous by late summer; indusia hood-like, attached on one side and arching over the sorus, fragile and quickly disintegrating

CYSTOPTERIDACEAE (in part, Cystopteris)



The introductory key below leads sometimes to a family but mostly to the 15 individual keys (A through O) which follow. When there are several genera in a family and only one of them will run at a given lead in a key, the name of the genus (or even of a species) is usually stated.

1. Plants strictly aquatic, the leaves or plant body entirely submersed or floating on the surface of the water (at most, the inflorescence and bracts, not leaves, held above the surface except in a few free floating species)[1]


1. Plants with at least some leaves (or stem if plant apparently leafless) above the water (but not free floating) or plants strictly terrestrial

2. Plants woody (trees, shrubs, and woody vines), with erect, trailing, or viny above-ground stems living through the winter and continuing to grow the next season [hence, leaves may be evergreen or deciduous]


2. Plants herbaceous, the perennial parts, if any, below or on the surface of the ground (to which the stems die back each year), not producing woody stems which survive the winter well above ground [hence, without aerial evergreen leaves (although there may be basal winter-green leaves)]

3. Plant lacking green color (often wholly parasitic or saprophytic) and the leaves none at flowering time or reduced to tiny scales)[2]


3. Plant with green color and the leaves usually developed (occasionally the stems photosynthetic, as in cacti)

4. Inflorescences producing only small bulblets or tufts of little leaves (or modified floral parts), but no flowers or fruit[3]


4. Inflorescences normal

5. Perianth parts (2), 3, (4), or 6 (never 5) and leaves (or other green photosynthetic parts when leaves are absent or reduced) parallel-veined (the 3 or more main veins running from base of blade to apex and ± parallel, with or without minute cross-veins), entire, simple[4]


5. Perianth parts various (often 5) but leaves netted-veined (or with only the midvein conspicuous), entire or toothed, simple or compound (the main veins, if more than 1, branching and ± reticulate)[5]

6. Inflorescence a dense “head” (either a true head or a spadix), consisting of few to many small sessile flowers on a common receptacle (not merely an elongate spike), subtended by 1 or more small or large bracts


6. Inflorescence not an involucrate head, or if head-like the individual flowers short-pediceled and/or the “head” not immediately subtended by 1 or more bracts

7. Plants leafless but with thick, fleshy, green stem segments often bearing strong spines


7. Plants not both leafless and with spiny fleshy stems

8. Inflorescence of “false flowers” consisting of small cup-like structures (uniform in texture and not composed of separate parts like bracts or scales) each bearing 1–5 glands on its rim (sometimes with additional petaloid appendages) and including 2 or more stamens and 1 central stalked 3-lobed pistil (which ripens into an exserted, 3-lobed capsule); sap milky[6]


8. Inflorescence various, but not composed of such structures; pistil only rarely stalked (and if so, not 3-lobed); sap various

9. Anthers and stigma fused into a central structure obscuring the individual reproductive parts; ovaries 2, ripening into follicles, the seeds each with a tuft of hairs (except Vinca); sap milky


9. Anthers and stigmas not fused to each other, of diverse but recognizable structure; ovaries, seeds, and sap various but not combined as above

10. Flowers unisexual, containing one or more stamens or pistils, but not both[7]


10. Flowers all or mostly bisexual, containing both stamen(s) and pistil(s) (although these may not all be equally mature at the same time)

11. Perianth none

12. Leaves deeply lobed or compound

13. Pistil 1, with 2 stigmas; sap yellow


13. Pistils several, each with 1 stigma; sap watery


12. Leaves unlobed (at most, blade cordate), entire

14. Flowers axillary; stamen 1; leaves opposite or whorled, ± sessile, linear to spathulate

PLANTAGINACEAE (Callitriche, Hippuris)

14. Flowers in nodding spike-like racemes; stamens 6–8; leaves alternate, petiolate with cordate blade


11. Perianth present (but not always conspicuous)

15. Perianth of only one series (calyx or corolla)[8]

16. Ovary inferior[9]


16. Ovary (or ovaries) superior


15. Perianth of two series (both calyx and corolla)

17. Ovaries 2 or more in each flower


17. Ovary 1 in each flower (styles or stigmas may be separate)

18. Ovary inferior


18. Ovary superior

19. Stamens more numerous than the petals


19. Stamens the same number as the petals or lobes (not lips) of the corolla, or fewer

20. Petals separate


20. Petals connate at least at the base

21. Corolla regular and the stamens the same number as its lobes


21. Corolla either bilaterally symmetrical or the stamens fewer than its lobes (not lips), or both conditions present




(Aquatic Plants with All Leaves Floating or Submersed, or Plants Free Floating)

1. Plants without distinct stem and leaves, free-floating at or below surface of water (except where stranded by drop in water level), the segments (internodes) small (up to 15 mm, but in most species much smaller), often remaining attached where budded from parent plant

2. Plant body once to several times equally 2-lobed or 2-forked

Ricciaceae (a family of liverworts)

2. Plant body not consistently dichotomous


1. Plants with distinct stem and/or leaves, mostly much larger

3. Plants free-floating (except "stranded" individuals), but with leaves borne above the water surface in a rosette, with roots in the water

4. Leaves densely hairy, sessile in the rosette

ARACEAE (Pistia stratiotes)

4. Leaves glabrous, with inflated petioles

PONTEDERIACEAE (Eichhornia crassipes)

3. Plants with leaves floating, submerged, or absent

5. Plants with floating leaves present (blades, or at least their terminal portions, floating on the surface of the water, usually ± smooth and firm in texture, especially compared with submersed leaves, or submersed leaves none)

6. Blades of some or all floating leaves on a plant sagittate or deeply lobed at base, or compound, or peltate

7. Floating blades compound (4-foliolate)

MARSILEACEAE (Marsilea quadrifolia) (a Pteridophyte)

7. Floating blades simple

8. Floating blades (at least some of them) sagittate (the apex and lobes acute) [Caution: Plants with sagittate leaves extending above the surface of the water do not belong in this key]


8. Floating (and any other) blades circular to ± elliptic in outline, peltate or rounded at apex with deep sinus at base

9. Leaves rounded at apex with deep sinus at base

10. Plants free-floating, forming interconnected masses with leafless shoots ending in turions; flowers with 3 white petals


10. Plants with rhizomes rooted in the substrate, lacking leafless turion bearing shoots; flowers with 4-many white (rarely pink) or yellow petals or petaloid sepals

11. Leaves and flowers with long petioles extending to a large fleshy rhizome rooted in soil


11. Leaves and flowers short petioles connecting to thin stems in the water.

12. Flowers white; leaves entire

RANUNCULACEAE (Caltha natans)

12. Flowers yellow; leaves slightly crenate

MENYANTHACEAE (Nymphoides peltata)

9. Leaves peltate

13. Leaves circular, large (1 dm or more in diameter); flowers yellow


13. Leaves elliptic, less than 1 dm in their longest dimension, flowers reddish or white


6. Blades of floating leaves all unlobed (at most subcordate at base), simple, the petiole marginal or (in ribbon-like leaves) none

14. Floating leaves small (less than 1 cm long), crowded in a terminal rosette; submersed leaves distinctly opposite; flowers solitary, axillary


14. Floating leaves larger, not in a rosette; submersed leaves alternate, basal, or absent; flowers mostly in a terminal inflorescence

15. Leaves narrow and ribbon-like, the blades many times as long as broad, without distinct petiole (though in some species a sheath surrounds the stem)

16. Leaves ± rounded at tip (even if tapered), the floating portion smooth and shiny, somewhat yellow-green to bright green when fresh, occasionally keeled but midvein scarcely if at all more prominent than others; leaf not differentiated into blade and sheath, the submersed portion similar to the floating but more evidently with a fine closely checkered pattern; flowers and fruit in spherical heads

TYPHACEAE (Sparganium)

16. Leaves sharply acute at tip, the floating portion rather dull, ± blue-green when fresh, with midrib; leaf including a sheath around stem and a membranous ligule at junction of sheath and blade; flowers and fruit in paniculate spikelets


15. Leaves (at least floating ones) with ± elliptic blades and distinct petioles

17. Leaves all basal; petals 3, white


17. Leaves cauline, alternate or opposite; petals 4–6, pink, yellow, or dull and inconspicuous (white in Caltha natans)

18. Flowers single on a pedicel, white 

RANUNCULACEAE (Caltha natans)

18. Flowers sessile in spikes, pink or dull and inconspicuous

19. Venation netted; flowers bright pink, in dense ovoid to cylindrical spikes

POLYGONACEAE (Persicaria amphibia)

19. Venation parallel; flowers dull, in narrow cylindrical spikes


5. Plants without any floating leaves, entirely submersed (except sometimes for inflorescences and associated bracts)

20. Leaves (or leaf-like structures) all basal and simple

21. Leaves definitely flat, several times as broad as thick (widest about the middle or parallel-sided)

22. Leaf blades not over twice as long as broad


22. Leaf blades more than twice as long as broad

23. Leaves stiff and erect or somewhat outcurved, less than 20 cm long

24. Base of leaf somewhat sheathing, with a membranous ligule (as in a grass) at base of spreading blade


24. Base of leaf not sheathing and with no ligule


23. Leaves limp, more than 20 cm long, ribbon like

25. Midvein not evident, all veins of essentially equal prominence, with the tiny cross-veins giving a checkered appearance to the leaf, which is thus uniformly marked with minute rectangular cells ca. 1–2 mm long or smaller

TYPHACEAE (Sparganium)

25. Midvein (and usually some additional longitudinal veins) evident, the veins not all of equal prominence, not dividing the leaf into minute rectangular cells

26. Leaves with the central third (or more) of distinctly different pattern (more densely reticulate) than the two marginal zones; plants dioecious, the staminate flowers eventually liberated from a dense inflorescence submersed at base of plant, the pistillate solitary on a long ± spiraled stalk which reaches the surface of the water; plants without milky juice


26. Leaves ± uniform in venation, not 3-zoned; plants monoecious, with emergent inflorescence of white-petaled flowers (but these scarce on plants with submersed tape-like leaves); plants often with milky juice


21. Leaves (or similar vegetative stems) filiform or terete or only slightly flattened (especially basally), elongate and limp to short and quill-like, less than twice as broad as thick

27. Major erect structures solitary, spaced along a simple or branched delicate rhizome, consisting either of rather yellowish stems bearing minute alternate bumps as leaves or of filiform leaves mostly buried in the substrate and with a few minute bladder-like organs

28. Leaves merely minute alternate bumps on stem; bladders not present; flowers sessile, inconspicuous, regular

HALORAGACEAE (Myriophyllum tenellum)

28. Leaves filiform, mostly buried in substrate (only the green tips, incurled when young, protruding); bladders (minute) usually present on the delicate branching rhizomes and buried leaf bases; flowers short-pediceled, showy (yellow or purple), bilaterally symmetrical

LENTIBULARIACEAE (Utricularia, couplet 2)

27. Major erect structures solitary to densely tufted, consisting of filiform or quill-like leaves or stems, with neither alternate bumps or bladders

29. Leaves very limp (retaining no stiffness when removed from water and hence irregularly sinuate, bent, or matted on herbarium specimens) though a stiffer straight stem may also be present, mostly more than 20 cm long, ca. 0.2–1 mm in diameter

30. Leaves (actually vegetative stems) terete their entire length, not expanded basally nor sheathing each other, but each separate and closely surrounded at base for ca. (0.6–) 1 cm or more by a very delicate membranous tubular sheath (this sometimes requiring careful dissection to distinguish); rhizome less than 2 mm in diameter; inflorescence (rare on plants otherwise entirely submersed) a single strictly terminal spikelet

31. Rhizome reddish, at least on older portions; leaves (vegetative culms) mostly over 20 cm long, very limp; fertile culm triangular in cross-section on emersed portion, much larger in diameter than the hair-like vegetative culms, but spikelet no thicker than culm

CYPERACEAE (Eleocharis robbinsii)

31. Rhizome whitish throughout; leaves often shorter, usually stiffer; fertile culms terete, no larger than the vegetative culms, but spikelet distinctly thicker than culm

CYPERACEAE (Eleocharis acicularis)

30. Leaves slightly expanded basally for ca. (0.7–) 2–10 cm, sheathing the next inner leaf at least dorsally (usually the sheath continued ventrally as an almost invisible membrane), with tiny ligule or pair of auricles at the summit; rhizome various; inflorescence a lateral spikelet or terminal cyme

32. Leaf somewhat flattened or grooved ventrally for at least a few cm above the sheath (± crescent-shaped in cross-section), with 1–5 longitudinal nerves evident, the tiny cross-veins connecting between nerves but not extending entirely across the leaf; sheath with a tiny ligule at summit; rhizome less than 2 mm in diameter; inflorescence a solitary lateral spikelet on a stiff wiry stem just above or near the surface of the water; flowers without petals and sepals; fruit an achene

CYPERACEAE (Schoenoplectus subterminalis)

32. Leaf terete above sheath, with no evident longitudinal veins, but numerous definite septa extending entirely across the blade (which shrinks between septa on drying); sheath with a minute pair of auricles at summit; rhizome ca. 2–5 mm thick; inflorescence an open cyme of many several-flowered heads on a very stout stem (several mm in diameter, over 50 cm tall); flowers with 6 tepals; fruit a capsule

JUNCACEAE (Juncus militaris)

29. Leaves usually firm (retaining stiffness when removed from water and hence straight or with an even curve in herbarium specimens), less (in most species much less) than 20 cm long, of various diameter

33. Leaves filiform throughout, not broader basally nor sheathing each other, solitary (rarely) or in small tufts along a filiform whitish rhizome, each leaf (actually a vegetative stem) closely surrounded at its base for ca. 6 mm or more by a very delicate membranous tubular sheath (this sometimes requiring careful dissection to distinguish); inflorescence (rare on completely submersed plants) a single terminal spikelet

CYPERACEAE (Eleocharis acicularis)

33. Leaves linear or tapered from base to apex, or if otherwise uniformly filiform then expanded at base or sheathing each other, without individual tubular sheaths as described above; inflorescence various

34. Leaf in cross-section appearing composed of 2 hollow tubes, linear (± parallel-sided), broadly rounded at tip; flowers bilaterally symmetrical, in a few-flowered raceme

CAMPANULACEAE (Lobelia dortmanna)

34. Leaf not (or rarely) of 2 hollow tubes, tapered and ± acute (or filiform); flowers regular and racemose, or solitary, or in a dense head or spike, or plant producing spores at base

35. Roots with prominent cross-septate appearance (checkered with fine transverse lines); inflorescence a small whitish or gray head (flowering in shallow or rarely deep water and on wet shores)


35. Roots not distinctly septate or cross-lined; inflorescence not as above

36. Leaves rather abruptly expanded at base to enclose sporangia, often dark green, composed of 4 hollow tubes (in cross-section), surrounding a hard corm-like stem; plant submersed (unless stranded), non-flowering

ISOETACEAE (Isoetes)(a Pteridophyte)

36. Leaves gradually and slightly expanded or grooved on one side at a somewhat sheathing base but not composed of 4 tubes nor enclosing sporangia and no corm-like stem present; plants (except Subularia) not flowering when submersed but only on wet shores

37. Leaves somewhat flattened at least basally, widest at the base, gradually tapered to sharp apex; plants with buried rhizome or none

38. Plants connected by slender rhizomes (ca. 1 mm or narrower); sheathing basal portion of leaf (ca. 7 mm or more) with pale membranous borders abruptly terminating (or with minute auricles); leaves often 4 cm or more long, somewhat flattened laterally below, with 2–3 conspicuous hollow tubes evident in cross-section; inflorescence (not on wholly submersed plants) a spreading cyme of solitary to paired 3-merous flowers

JUNCACEAE (Juncus pelocarpus)

38. Plants without rhizomes; sheath not abruptly auricled; leaves less than 4 cm long, somewhat flattened dorsiventrally (especially toward base), with numerous small hollow areas of irregular size; inflorescence (often submersed) a few- (often only 2-) flowered raceme of 4-merous flowers

BRASSICACEAE (Subularia aquatica)

37. Leaves ± terete, scarcely or no wider at base than at middle, of ± uniform width at least to the middle (or even slightly thicker there before tapering to apex); plants with rhizomes or stolons at, near, or above surface of substrate

39. Plants with green stolons strongly arching above substrate; leaves filiform, ± uniform in diameter, ca. 0.5–1 mm thick, truncate at tip

RANUNCULACEAE (Ranunculus reptans)

39. Plants producing delicate horizontal white to green stolons at or near (above or below) surface of substrate (in addition to stouter short rhizome); leaves ca. 0.7–3 mm thick at middle, whence tapered to apex


20. Leaves cauline, simple or compound (basal and dissected in one species)

40. Leaves compound, dissected, forked, or deeply lobed

41. Leaves apparently in a basal rosette, few

APIACEAE (Sium suave)

41. Leaves definitely cauline: opposite, whorled, or alternate

42. Leaves all or mostly opposite or whorled

43. Leaves (or whorled branches) rolled inward at tip when young, bearing tiny stalked bladders; flowers emersed, bilaterally symmetrical, purple or yellow


43. Leaves not inrolled at tip, without bladders; flowers various but not as above

44. Petiole evident (5–15 mm long on well developed leaves), the blade fan-shaped and much dissected; flowers emergent, white


44. Petiole absent or nearly so, the blade pectinate (with straight central axis following midrib, once-pinnatifid or comb-like on both sides) or much dissected or soon forking once or twice; flowers inconspicuous or yellow

45. Leaves once or twice dichotomously forked, the segments usually sparsely toothed along one edge; flowers inconspicuous, axillary, submersed


45. Leaves not dichotomously forked, the segments entire; flowers emersed or (rarely) submersed

46. Leaves pectinate; flowers inconspicuous, in all but the rarest species emersed in terminal spike

HALORAGACEAE (Myriophyllum)

46. Leaves with no definite central axis, much dissected; flowers emersed in a showy yellow head (usually with at least one pair of merely serrate opposite leaves below it)

ASTERACEAE (Bidens beckii)

42. Leaves definitely all alternate

47. Leaves with a definite central axis (following midvein); flowers various

48. Leaves pectinate (the lateral segments not again branched); flowers inconspicuous, axillary; fruit a nutlet

HALORAGACEAE (Proserpinaca)

48. Leaves with lateral segments further narrowly divided; flowers with white corollas, in emersed raceme; fruit a silique

BRASSICACEAE (Rorippa aquatica)

47. Leaves with no definite central axis (except sometimes after initially forking at the stem); flowers emersed, with conspicuous corolla

49. Petiole present (sometimes very short), ± adnate to a stipular sheath; plants without bladders; flowers regular, white or yellow, with numerous separate carpels forming achenes


49. Petioles and stipular sheaths absent; plants with small stalked bladders on leaves or on separate branches; flowers bilaterally symmetrical, yellow or purplish, with a single pistil producing a capsule


40. Leaves simple, unlobed, usually entire (toothed in a few species)

50. Leaves much reduced, ± scale-like, not over 7 mm long, never distinctly opposite or whorled

51. Leaves minute, yellowish, merely widely spaced bumps or scales on stem

HALORAGACEAE (Myriophyllum tenellum)

51. Leaves up to 7 mm long, green or brownish, loosely overlapping

(aquatic mosses & liverworts)

50. Leaves much longer or distinctly opposite or whorled (or both conditions)

52. Leaves alternate, with ligule-like stipules (these wholly adnate to leaves in Ruppia)

53. Leaf blades ± filiform, terete or at least half as thick as broad, and the stipule adnate to leaf base for 10–30 mm or more, forming a sheath around the stem


53. Leaf blades definitely flattened and several times as broad as thick (even if narrow), or stipule little if at all adnate to blade (or both conditions)

54. Blades flattened, ribbon-like (up to 5 or even 7.5 mm wide), with no definite midrib (no central vein more prominent than others except rarely toward base); flowers solitary, rare, cleistogamous in axils of submersed leaves or (these almost never on submersed plants) with 6 bright yellow tepals


54. Blades flattened with a definite midrib or filiform; flowers in spherical or cylindrical spikes, neither cleistogamous nor with showy yellow perianth


52. Leaves opposite or whorled, without stipules

55. Leaves nearly filiform, not over 0.5 mm wide, very gradually tapered from base to apex but not abruptly expanded basally, perfectly smooth; plants perennial by slender rhizomes; flowers axillary, 1 staminate flower (a single stamen) and (1) 2–several carpels at a node; fruit slightly curved and minutely toothed on convex side


55. Leaves broader; or if filiform then abruptly expanded basally and with apiculate or toothed margins, the plants annual, and the fruit solitary and ellipsoid

56. Leaves definitely whorled

57. Whorled structures (“branches”) cylindrical, elongate, usually stiff with calcium deposits; plants with distinctive musky odor

Characeae (a family of algae)

57. Whorled structures (true leaves) flattened, short (not over 20 mm long) or elongate and very limp; plants without odor

58. Leaves 6–12 (usually 9) in a whorl, not over 2.5 mm wide, ca. 12–25 times as long as wide; flowers bisexual, apetalous, sessile in axils of emersed leaves or bracts


58. Leaves mostly 3–4 (rarely 6) in a whorl, 0.8–5 mm wide, at most 10–13 times as long; flowers bisexual or unisexual, but with petals

59. Leaves mostly 3 (rarely 6) in a whorl, very thin (2 cell layers) and delicate; stem round (not angled), smooth; flowers unisexual, with 3 often pink petals, at least the pistillate long-stalked from entirely submersed stem


59. Leaves mostly 4 in a whorl, stiff and firm; stem 4-sided, often with minutely retrorse-scabrous angles; flowers bisexual, with 3–4 white petals (usually not developed on wholly submersed plants)


56. Leaves opposite (in some species, with bushy axillary tufts of leaves which may give a falsely whorled appearance)

60. Largest leaves at least 1–4 cm long, with distinct petiole and expanded, entire blade

61. Leaf blades ± orbicular, with orange to black glandular dots especially beneath; flowers 5-merous with showy yellow petals and superior ovary

MYRSINACEAE (Lysimachia nummularia)

61. Leaf blades ± diamond-shaped, without glandular dots; flowers 4-merous, inconspicuous, with inferior ovary

ONAGRACEAE (Ludwigia palustris)

60. Largest leaves smaller, or sessile, or toothed (or all of these)

62. Leaves large, 3–13 cm long, 5–20 mm wide

63. Leaves sessile and clasping, limp, at most obscurely and remotely toothed; flowers (rarely present on plants with all foliage submersed) in axillary racemes

PLANTAGINACEAE (Veronica anagallis-aquatica)

63. Leaves sessile, clasping, tapered, or petioled, stiff, often regularly crenate or toothed; flowers various

(Submersed individuals of normally terrestrial or emergent plants, chiefly LAMIACEAE)

62. Leaves small (shorter or narrower than the above, or usually both)

64. Leaves linear and bidentate at apex when well submersed, often becoming obovate, ± weakly 3-nerved, and not necessarily bidentate toward summit of stem (or in floating rosettes); fruit solitary in axils, somewhat heart-shaped, of two 2-seeded segments


64. Leaves filiform to orbicular or tapered from base to apex, but essentially uniform on a plant and if linear not bidentate at apex; fruit various

65. Leaves at least 3 times as long as wide, broader at base than at middle; fruit absent or solitary in axils of leaves and ± ellipsoid

66. Leaves (especially lower ones) ± evenly tapered from broad base to minutely but bluntly bidentate apex, 3–10 times as long as wide, strictly entire, not subtending axillary tufts of leaves or fruit; plant often with a few scattered pale glandular dots on surface toward upper portion

PLANTAGINACEAE (Gratiola aurea)

66. Leaves filiform to linear-lanceolate, ± expanded at very base, acute or apiculate at apex, at least 6 times as long as wide, minutely apiculate to conspicuously toothed on margins, usually subtending axillary tufts of leaves and/or flowers or ellipsoid fruit; plant without glands on surface


65. Leaves less than 3 times as long as wide, often nearly round

67. Stems forming moss-like mats but the erect or ascending tips (above rooted nodes) less than 3 cm long; leaves with at most 1 weak nerve; stipules minute but usually evident with some leaves; flowers axillary, inconspicuous


67. Stems greatly elongate (generally 10–30 cm); leaves more evidently veined; stipules none; flowers terminal, yellow (but usually absent on plants with all leaves submersed)

68. Stems stiffly erect; leaves weakly pinnately veined (with evident midvein), with reddish to blackish shiny dots or flecks (these often also on stem, but most prominent on emersed leaves)

MYRSINACEAE (Lysimachia terrestris and L. thyrsiflora)

68. Stems ± lax; leaves 3-nerved, without dark dots or flecks (though emersed leaves have translucent dots)

HYPERICACEAE (Hypericum boreale)



(Woody Plants)

Included here are all plants that are woody in the traditional sense; forming above ground twigs with secondary growth and winter buds. A few soft-wooded species with greenish stems such as Pachysandra and Ruta are also included. These will be keyed as herbaceous plants as well. This key also includes small evergreen trailers such Vinca, Linnaea, and Mitchella.

1. Leaves scale-like (ca. 4 mm or less long and often appressed/imbricate) or needle-like (stiff and filiform to narrowly linear, less than 2.7 mm broad), evergreen (except in Tamaricaceae and Larix in Pinaceae)

2. Plant with leaves scale-like (or less than 3 mm long)

3. Leaves alternate

4. Flowers yellow; leaves ± densely pubescent

CISTACEAE (Hudsonia)

4. Flowers pink; leaves glabrous


3. Leaves opposite or whorled

5. Plants fragrant when crushed, producing small dry or berry-like female cones but never flowers or true fruit


5. Plants not fragrant, producing flowers and fruit in season

6. Plant a parasite, less than 1.5 cm high, on branches of conifers, blooming in very early spring without showy perianth

SANTALACEAE (Arceuthobium)

6. Plant a small terrestrial shrub, blooming in late summer with showy pink flowers


2. Plant with leaves needle-like or narrowly linear (over 3 mm long)

7. Leaves opposite or whorled


7. Leaves alternate or in clusters

8. Plant a prostrate shrub; leaves less than 7 mm long; fruit a dark several-seeded berry (the seeds enclosed)

ERICACEAE (Empetrum)

8. Plant a tree or bushy shrub; leaves all or mostly 7 mm or longer; “fruit” a cone or a bright red 1-seeded fleshy structure (with the seed exposed)

9. Seed solitary in a red, fleshy, cup-like aril; leaves flattened, with strongly decurrent base, persistent, appearing 2-ranked, all green on both sides (may be yellowish beneath)


9. Seeds borne on scales of a dry woody cone; leaves flattened or not (but if so, not strongly decurrent, readily falling when dry, not 2-ranked, except the deciduous Taxodium, and/or with white lines beneath)

10. Leaves evergreen (except Larix with leaves spirally arranged), arranged in clusters, spiraled around the stem, or in flattened 2-ranked sprays; cones slightly to very much longer than wide, the cone scales flattened


10. Leaves deciduous, arranged in flattened 2-ranked sprays; cones globular, with peltate cone scales


1. Leaves with expanded (or dissected) blades, neither scale-like nor needle-like, if linear, then herbaceous, not stiff; deciduous or occasionally evergreen; occasionally absent at flowering time

11. Leaves opposite or whorled or nearly so (evident from scars if leaves not expanded at anthesis)

12. Flowers appearing before leaves are expanded

13. Perianth of both calyx and corolla

14. Calyx and corolla lobes 4; corolla lobes ca. 1.5–2.5 cm long; stamens 2; fruit a capsule

OLEACEAE (Forsythia)

14. Calyx and corolla 5-lobed (or corolla bilabiate) or petals separate; corolla lobes or petals longer than1.5 cm; stamens 5; fruit a samara or a drupe or berry

15. Ovary superior; petals separate; flowers often unisexual


15. Ovary inferior; petals united; flowers bisexual

16. Flowers numerous in terminal cymes

ADOXACEAE (Sambucus)

16. Flowers in pairs on axillary peduncles


13. Perianth of only one cycle of parts, or none

17. Inflorescence an ament (catkin); bud scale 1

SALICACEAE (Salix purpurea)

17. Inflorescence otherwise, of clustered or pediceled flowers but not an elongate ament; bud scales more than 1

18. Flowers staminate or bisexual

19. Stamens 2 (–4)

OLEACEAE (Fraxinus)

19. Stamens 5 or more

20. Calyx lobes 4; stamens 8; buds scurfy-pubescent


20. Calyx lobes 5; stamens ca. 5–10; buds not scurfy-pubescent


18. Flowers pistillate

21. Ovary with 2 divergent lobes


21. Ovary unlobed

22. Flowers perigynous, the floral tube with a prominent disk at its summit; buds scurfy-pubescent; young fruit rotund


22. Flowers not perigynous, without a prominent disk; buds not scurfy; young fruit strongly flattened

OLEACEAE (Fraxinus)

12. Flowers appearing after the leaves have expanded (i.e., leaves present)

23. Leaves compound

24. Plant a climbing or trailing vine

25. Leaves pinnately compound; corolla well developed, showy, bilaterally symmetrical; flowers bisexual; stamens 4; pistil 1


25. Leaves all or mostly trifoliolate; corolla none (though calyx may be showy and regular); flowers unisexual; stamens and pistils numerous


24. Plant erect, not a vine

26. Petals none; fruit a samara (winged)

27. Ovary 2-lobed; fruit united in pairs; stamens ca. 5–10; leaflets usually 3–5

SAPINDACEAE (Acer negundo)

27. Ovary not lobed; fruits not paired; stamens 2 (–4); leaflets 5–11

OLEACEAE (Fraxinus)

26. Petals well developed and conspicuous; fruit various but not a samara

28. Petals united; leaves pinnately compound with 5 or more leaflets; fruit fleshy

ADOXACEAE (Sambucus)

28. Petals separate; leaves trifoliolate or palmately or pinnately compound; fruit dryish

29. Leaves pinnately compound, leaflets finely crenulate to ± entire; dioecious trees

RUTACEAE (Phellodendron)

29. Leaves trifoliolate or palmately compound; leaflets sharply toothed; flowers bisexual

30. Leaflets 3; flowers in drooping panicles; petals and stamens 5; fruit an inflated, indehiscent, inflated bladdery capsule


30. Leaflets 5–7 (–9); flowers in erect panicles; petals 4–5, stamens 6–8; fruit a firm, leathery, usually 1–2-seeded capsule


23. Leaves simple

31. Stamens more numerous than the petals or lobes of the corolla (or of the calyx if corolla is absent), or flowers strictly pistillate

32. Petals united


32. Petals separate or none

33. Stamens usually more than 10; corolla yellow or white

34. Leaves scale-like; style 1; ± prostrate shrub less than 2 dm tall

CISTACEAE (Hudsonia)

34. Leaves well developed; styles 3–5 (sometimes ± coherent); shrubs to 2–3 m tall

35. Flowers yellow; petals usually 5; leaves entire


35. Flowers white; petals usually 4 (–5); leaves toothed or ciliate-margined (or both)

36. Ovaries (1–) 4; fruit of 1–4 dry, shiny black drupes; leaves conspicuously doubly serrate

ROSACEAE (Rhodotypos)

36. Ovary 1; Fruit a capsule; leaves ± entire (but ciliate) or dentate with irregularly spaced, often inconspicuous teeth


33. Stamens 10 or fewer, or flowers strictly pistillate; corolla pink, green, greenish-yellow, or white

37. Leaves palmately lobed, toothed; fruit a samara, united in pairs


37. Leaves unlobed, entire or toothed; fruit a berry or capsule, not paired

38. Plant clearly a bushy shrub, with scurfy or stellate pubescence

39. Flowers unisexual, inconspicuous, greenish-yellow, very early in spring; fruit a berry


39. Flowers bisexual, showy, white or pale pink, after the leaves have expanded; fruit a capsule


38. Plant barely woody at base, glabrous to somewhat tomentose but not scurfy or stellate pubescent; flowers bisexual with showy pink (to white) petals; fruit a capsule

40. Leaves evergreen, very shiny, toothed; stigma nearly sessile

ERICACEAE (Chimaphila)

40. Leaves deciduous, ± dull, entire; stigma on an elongate style


31. Stamens the same number as the lobes or petals of the corolla or fewer

41. Petals separate

42. Flowers in terminal inflorescences


42. Flowers axillary

43. Fruit a red to purple capsule, the seeds enclosed in a red or orange aril; styles unlobed; stamens alternating with the petals


43. Fruit a dry inconspicuous capsule or fleshy and indehiscent, the seeds not arillate; styles often lobed; stamens opposite the petals


41. Petals united

44. Ovary inferior

45. Flowers and fruits in dense spherical peduncled heads or paired at the ends of trailing branches; leaves entire, with broad stipules between the petiole bases


45. Flowers and fruits pediceled in small clusters or ± branched inflorescences; leaves entire or toothed, with stipules none or slender and partly adnate to petioles

46. Leaves of flowering shoots or flowering portions of shoots entire or somewhat undulate or sinuous, not sharply or regularly toothed


46. Leaves with margins lobed, ± regularly toothed, crenate, or finely crenulate, or at least with regular minute gland-like teeth

47. Calyx lobes up to 1.5 mm long and broadly triangular to broadly rounded or virtually absent; corolla rotate (flat with very short tube); style very short or essentially absent; fruit fleshy with one pit

ADOXACEAE (Viburnum)

47. Calyx lobes (1.6–) 2–6.5 (–7.5) mm long, linear or narrowly lanceolate; corolla tubular; style elongate, conspicuous; fruit dry

48. Corolla yellow, turning orange or even flushed with red; ovary and fruit glabrous (occasionally pubescent)


48. Corolla pink (sometimes pale); ovary and fruit densely glandular-bristly or bristly


44. Ovary superior

49. Corolla bilaterally symmetrical

50. Plant a tree with large cordate ± whorled leaves


50. Plant a mint with opposite leaves and scarcely woody at the base

LAMIACEAE (some Hyssopus or Thymus)

49. Corolla regular

51. Ovaries 2 (but styles and stigmas united); plant an evergreen creeper with blue flowers solitary in the leaf axils


51. Ovary 1; plant erect, with flowers in inflorescences

52. Stamens 2; leaves entire


52. Stamens 4; leaves toothed


11. Leaves alternate

53. Leaves deeply dissected into linear-filiform segments, aromatic

ASTERACEAE (Artemisia)

53. Leaves simple, compound (then leaflets broader than linear-filiform), or absent at anthesis, aromatic or not

54. Fruit a syconium (fig), a hollow pear-shaped structure with a terminal pore and tiny flowers on the inside; rarely escaped dieback shrub with scabrous, lobed leaves


54. Fruit various, but not a syconium, flowers external; habit and leaves various

55. Plants dioecious

56. Plant a climbing vine (or trailing in absence of support for tendrils or twining stem)

57. Stems with tendrils

58. Leaves entire; stems prickly (at least below); perianth of 6 tepals


58. Leaves toothed; stems unarmed; perianth of 5 petals and 5 (sometimes vestigial) sepals


57. Stems without tendrils (aerial roots may be present along stem)

59. Leaves trifoliolate; plants climbing by adventitious roots (POISONOUS)

ANACARDIACEAE (Toxicodendron)

59. Leaves simple or with more than 3 leaflets; plants climbing by twining stems

60. Leaves pinnately veined, simple


60. Leaves palmately veined or compound

61. Sepals and petals each 6; leaves ± peltate (petiole attached in from margin of the blade), at most somewhat lobed but not toothed


61. Sepals (often vestigial) and petals each 5; leaves with marginal petiole, toothed


56. Plant ± erect, not climbing

62. Flowers (at least the male ones) in cylindrical to nearly spherical aments (catkins)

63. Twigs and leaves with milky sap; calyx minute; leaves palmately or pinnately veined


63. Twigs and leaves with watery sap; calyx none; leaves pinnately veined

64. Crushed foliage pungently aromatic; twigs resin-dotted; fruit an achene or dry drupe


64. Crushed foliage in most species not at all aromatic; twigs without resinous dots (may be generally shiny); fruit a capsule


62. Flowers not in aments

65. Leaves compound, present at anthesis

66. Leaves even-pinnately compound or bipinnate; carpel 1, ripening into a large, flat pod

FABACEAE (Gleditsia)

66. Leaves odd-pinnately compound, trifoliolate, or palmately compound; carpels more than 1, the fruit various (not a legume pod)

67. Leaves palmately compound

ARALIACEAE (Eleutherococcus)

67. Leaves trifoliolate or pinnately compound

68. Leaves punctate with translucent oil glands; stems spiny in common species


68. Leaves without translucent oil dots; stems unarmed

69. Leaflets nearly or quite entire except for one or more coarse teeth near the base, each with a large gland beneath; fruit a samara


69. Leaflets ± regularly toothed (glandless) or entire; fruit a small smooth to glandular-pubescent drupe; plant a native shrub (SOME SPECIES POISONOUS)


65. Leaves simple, or unexpanded at anthesis

70. Stems with paired stout, broad-based spines at each node

RUTACEAE (Zanthoxylum)

70. Stems lacking spines or prickles, though sometimes the twigs with apical thorns

71. Flowers pistillate

72. Calyx and corolla both present (the former sometimes very small and inconspicuous)

73. Inflorescences terminal, ± crowded or many-flowered


73. Inflorescences axillary

74. Stigma nearly or quite sessile


74. Stigma clearly on an elongate style

75. Leaves entire; style simple


75. Leaves closely toothed; style divided above the middle


72. Calyx and corolla not differentiated, or absent

76. Perianth of 6 parts; bruised twigs and leaves spicy-aromatic


76. Perianth of 3–5 parts or none; bruised parts not aromatic

77. Style and stigma 1; leaves entire

78. Stigma nearly or quite sessile


78. Stigma on an elongate style


77. Style divided above, stigmas 2–4; leaves toothed (at least on apical half)

79. Leaf blades asymmetrical at base


79. Leaf blades ± symmetrical at base


71. Flowers staminate

80. Stamens more numerous than the sepals or the petals (or perianth none)

81. Perianth none or minute; stamens usually 12; bruised parts not aromatic


81. Perianth conspicuous (yellow, of 6 parts); stamens 9; bruised twigs and leaves spicy-aromatic


80. Stamens the same number as the perianth parts (same as the petals if both sepals and petals present)

82. Inflorescences terminal, ± crowded or many-flowered


82. Inflorescences axillary

83. Stamens alternate with the sepals (opposite the petals if any)


83. Stamens opposite the sepals (alternate with the petals if any)

84. Leaf blades ± symmetrical at base, entire or toothed


84. Leaf blades asymmetrical at base, toothed (at least on apical half)


55. Plants not dioecious, the flowers either bisexual or unisexual (if the latter, then both sexes on the same individual)

85. Flowers (at least the staminate) in aments or dense spherical heads (always unisexual and individually inconspicuous)

86. Staminate flowers in dense spherical heads

87. Leaves pinnately veined, with one midrib and lateral veins each ending in a single tooth; pistillate flowers in small clusters


87. Leaves palmately veined, with 3–5 principal veins; pistillate flowers in spherical heads

88. Leaves prominently 3-veined just above the base, coarsely toothed with 3 (–5) shallow lobes or essentially unlobed; winter buds cone shaped, with a single bud scale


88. Leaves 5-veined just above the base, finely and uniformly toothed with usually 5 (–7) deep lobes; winter buds with several scales.


86. Staminate flowers in cylindrical to ellipsoid aments

89. Pistillate flowers solitary or in small clusters; styles 3 or leaves compound

90. Leaves pinnately compound; styles 2


90. Leaves simple (may be deeply lobed); styles usually 3


89. Pistillate flowers in aments, heads, or cone-like structures (in Corylus, the red styles protruding from an ament resembling a leaf bud); styles 2; leaves simple

91. Twigs and leaves with milky sap; calyx minute, 4-parted; leaves palmately veined (or fruit in a large spherical fleshy structure)


91. Twigs and leaves with watery sap; calyx usually none or 2-parted; leaves pinnately veined (fruit in aments or small clusters)


85. Flowers not in aments or heads (often bisexual and/or conspicuous)

92. Perianth none or apparently of a single series of parts

93. Leaves compound

94. Plant a vine with twining or scrambling stems; leaves palmately 5-foliolate


94. Plant erect, not twining; leaves pinnately or bipinnately compound

95. Stem prickly; plant shrub-like; fruit fleshy, in umbels


95. Stem unarmed; plant a weedy tree; fruit a samara, in large panicles


93. Leaves simple (or absent at anthesis)

96. Stamens more numerous than the segments or lobes (if any) of the perianth (or perianth none)

97. Plant a twining vine; perianth bilaterally symmetrical


97. Plant erect, not a vine; perianth regular

98. Perianth minute


98. Perianth well developed

99. Stamens 8; perianth lobes 4 (or essentially none)


99. Stamens 5–7 or 9; perianth lobes or segments 5 or 6

100. Leaves densely tomentose beneath, revolute; perianth segments 5

ERICACEAE (Rhododendron)

100. Leaves slightly if at all pubescent, not revolute; perianth segments 6


96. Stamens the same number as the lobes or segments of the perianth

101. Styles 2, 3, or 5

102. Evergreen subshrubs; styles 3


102. Deciduous shrubs or trees, styles 2 or 5

103. Stems prickly; fruit fleshy, in umbels


103. Stems unarmed; fruit a samara or drupe, solitary or in small clusters

104. Leaves with prominent, straight ± parallel lateral veins running into the principal teeth; flowers bisexual, the perianth shallowly lobed; ovary flattened and winged; fruit a samara


104. Leaves with lateral veins curved and ascending, weaker and the branches anastomosing near the margins; flowers usually unisexual, the perianth lobed nearly or quite to the base; ovary not flattened, fruit a drupe


101. Style 1 (may be branched above)

105. Stems prickly


105. Stems lacking prickles, though sometimes the twigs with apical thorns

106. Plant a vine, climbing or trailing by tendrils


106. Plant an erect shrub or tree

107. Inflorescences terminal


107. Inflorescences lateral

108. Leaves beneath and branchlets silvery-scurfy; stamens 4


108. Leaves and branchlets glabrous or nearly so, not scurfy; stamens 4–6

109. Stamens alternating with the sepals


109. Stamens opposite the sepals


92. Perianth clearly differentiated into calyx and corolla

110. Ovaries at least 3, distinct

111. Sepals and petals each 5; leaves simple and toothed or compound; bud scales several


111. Sepals 3, petals 6; leaves simple, entire; bud scales none or 2

112. Leaves unlobed, estipulate; flowers dark purplish; fruit fleshy; buds naked


112. Leaves 4-lobed, stipulate (the stipules leaving a scar surrounding each node); flowers greenish yellow; fruit dry, in a cone-like structure; bud scales 2


110. Ovary 1

113. Corolla bilaterally symmetrical (or petal only 1); stamens 10 (usually with some of the filaments connate)


113. Corolla essentially regular; stamens various

114. Petals united

115. Stamens more numerous than the corolla lobes

116. Leaves with stellate pubescence beneath, young twigs stellate-pubescent; pith of older twigs chambered; fruit large (over 2 cm long), dry, 4-winged


116. Leaves and twigs glabrous or pubescent but not stellate; pith solid; fruit small, dry or fleshy but not winged


115. Stamens the same number as the corolla lobes

117. Stamens adnate to the corolla (and falling with it if the corolla is deciduous); plants vining to shrubby; fruit a red berry or drupe

118. Flowers white, on short (< 5 mm) pedicels; leaves toothed


118. Flowers purple (except in rare albinos), pedicels > 7 mm; leaves entire-margined (though sometimes lobed)


117. Stamens free from the corolla; plant an erect or trailing shrub (not climbing); fruit various

119. Stigma on a well developed style; fruit a capsule


119. Stigma nearly sessile; fruit a red drupe


114. Petals separate

120. Ovary at least partly inferior

121. Stamens more than the number of petals

122. Style 1

123. Petals united; unarmed small to large shrubs

ERICACEAE (Vaccinium)

123. Petals free; thorny tree or large shrub

ROSACEAE (Crataegus monogyna)

122. Styles 2–5


121. Stamens the same number as the petals

124. Petals 4

125. Flowers white, in terminal cymes, blooming in early to mid-summer; fruit fleshy; leaves entire


125. Flowers yellow, in small axillary clusters, blooming in late fall; fruit a capsule; leaves with rounded teeth


124. Petals 5

126. Flowers in umbels, umbels either solitary or arranged in larger inflorescences


126. Flowers in racemes, small axillary clusters, or domes or flat-topped corymbs

127. Flowers in racemes or small axillary clusters; small shrubs less than 2 m tall


127. Flowers in terminal, domed or flat-topped corymbs; large shrubs or small trees more than 2 m tall

ROSACEAE (Crataegus)

120. Ovary entirely superior

128. Stamens more than twice as many as the petals

129. Corolla yellow; fruit a capsule


129. Corolla white to pink; fruit indehiscent

130. Inflorescence apparently borne at the middle of a tongue-shaped bract; leaves palmately veined


130. Inflorescence borne normally; leaves pinnately veined


128. Stamens twice as many as the petals or fewer

131. Leaves compound

132. Leaves even-pinnate or even-bipinnate; fruit a large woody legume (pod splitting on 2 sutures)


132. Leaves odd-pinnate, trifoliolate, or palmate; fruit a samara, drupe, berry, or 4–5-lobed capsule

133. Leaflets nearly or quite entire except for one or more coarse teeth near the base, each with a large gland beneath; fruit a samara


133. Leaflets toothed or entire but without large glands; fruit various (a samara only in trifoliolate Ptelea)

134. Inflorescences terminal

135. Leaves twice pinnatifid; fruit a 4–5-lobed capsule; soft wooded subshrub


135. Leaves trifoliolate or once pinnate; fruit a samara or dry drupe; shrubs or small trees

136. Fruit a samara, in loose open cymes; leaves trifoliolate, punctate with translucent oil glands


136. Fruit a glandular-pubescent drupe, in dense panicles; leaves pinnately compound, without translucent glands


134. Inflorescences lateral or axillary

135. Leaflets strongly spiny-toothed; flowers yellow


137. Leaflets without spines; flowers greenish yellow

138. Leaves palmately compound with mostly 5–7 leaflets, if trifoliolate then leaflets sharply toothed or pinnately lobed; plant a vine with tendrils; stamens opposite the petals (i.e., alternate with the sepals)

VITACEAE (Parthenocissus)

138. Leaves trifoliolate or pinnately compound with entire or nearly entire leaflets; plant a shrub or vine with adventitious roots (not tendrils); stamens alternating with the petals (i.e., opposite the sepals) (POISONOUS)

ANACARDIACEAE (Toxicodendron)

131. Leaves simple

139. Styles 2, separate to the base; petals 4, yellow, linear


139. Style 1 or 3 (may be lobed or cleft at summit); petals various

140. Stems spiny; flowers yellow, 6-merous


140. Stems unarmed; flowers white, pink, or greenish, 4–5-merous

141. Stamens more numerous than the petals; inflorescence an umbel or raceme; plant a low evergreen subshrub

142. Petals 5; stamens 10


142. Petals 4; stamens 6, 4 long and 2 short


141. Stamens the same number as the petals; inflorescence various; plant a bushy shrub, deciduous except in Rhododendron

143. Leaves evergreen, densely white- or brown-tomentose beneath, revolute

ERICACEAE (Rhododendron)

143. Leaves deciduous, glabrous or nearly so, with flat margins

144. Flowers in large terminal panicles; leaves rounded or even emarginate at apex, entire


144. Flowers in umbellate or cymose clusters or solitary, in the leaf axils or sometimes axillary and terminal; leaves ± acute at apex, often toothed

145. Stamens alternating with the sepals (i.e., opposite the petals); style 3-lobed


145. Stamens opposite the sepals (i.e., alternating with the petals); style nearly or quite absent




(Herbaceous Plants Lacking Both Green Color (or the green color obscured by other pigments) and Developed Leaves at Flowering Time)

1. Plants not anchored in the ground, solely parasitic on and attached to stems of other plants at maturity

2. Stem up to 15 mm long, with minute opposite leaves (scale-like); flowers in May, unisexual (plants dioecious), the staminate with stamens adnate to calyx lobes, the pistillate with inferior ovary; parasites on conifers

SANTALACEAE (Arceuthobium)

2. Stem elongate, with minute alternate leaves; flowers in late summer, bisexual, the stamens partly adnate to corolla and the ovary superior; parasites on flowering plants


1. Plants clearly anchored in the ground, not attached to other above-ground plants

3. Stem buried in ground; flowers in late fall or late winter or early spring (green leaves from rhizome or corm appearing in spring after flowering).

4. Flowers tiny, crowded in a spadix with a nearly or partly buried hood-like brownish or mottled spathe; stamens 4; plant with skunk-like odor

ARACEAE (Symplocarpus)

4. Flowers large, pink, borne singly; spathe absent; stamens 6; plant lacking strong odor.


3. Stem or flower stalk above ground; flowers later, solitary or in a few- to many-flowered raceme, umbel, or head; stamens various; plant with odor, if any, not skunk-like

5. Flowers completely 3-merous and regular, in an umbel on a naked peduncle arising from an underground, onion-smelling bulb


5. Flowers not completely 3-merous, regular or bilaterally symmetrical, not in an umbel, on aerial stems

6. Scale-like leaves (and branches if any) opposite; flowers less than 5 mm long

7. Stem thick and fleshy, appearing jointed, the flowers deeply embedded in it


7. Stem normal, slender and wiry, the flowers not at all embedded in it

8. Sepals and petals each 5, separate; stamens 5–10; styles 3

HYPERICACEAE (Hypericum gentianoides)

8. Sepals and petals each 4 and each series connate basally; stamens 4; style 1


6. Scale-like leaves alternate (or apparently none); flowers of various size

9. Inflorescence a single dense, short spike with spirally arranged scales; flowers lacking petals and sepals; stem with tubular sheaths at base

CYPERACEAE (Eleocharis)

9. Inflorescence of normal flowers not aggregated into a single dense spike, flowers with at least tiny petals, often showy; stem without tubular sheaths at base (except some Orchidaceae)

10. Flowers in a single involucrate head; outer flowers (rays) strap-like, of united petals; calyx none but a pappus of hair-like bristles present; stamens fused in a ring around the style

ASTERACEAE (Tussilago)

10. Flowers not in a single involucrate head, solitary in the leaf axils, individually pedunculate or single and terminal on a stem; all alike; calyx present (sometimes tiny); stamens separate

11. Petals 5, mostly united in a tube, the flower slightly to distinctly bilaterally symmetrical, not spurred; stamens 4


11. Petals 3–5 but not united in a tubular corolla, the flower regular or strongly bilaterally symmetrical (sometimes spurred); stamens various

12. Perianth strongly bilaterally symmetrical; stamens 1–2

13. Sepals and petals 3, the lower petal a definite lip, the others little modified; ovary inferior; plants of various habitat but not aquatic; perianth of various color


13. Sepals apparently 2 and petals 5, but corolla basically 2-lipped; ovary superior; plants of wet shores and bog pools, with perianth yellow or purple


12. Perianth regular; stamens 4–10

14. Corolla at least 5 mm long; stamens 8–10


14. Corolla less than 5.5 mm long; stamens 4

15. Flowers sessile; plant of wet lake shores, nearly or quite aquatic; stigmas 4, conspicuously exposed (corolla barely 2 mm long); fruit an indehiscent nutlet

HALORAGACEAE (Myriophyllum tenellum)

15. Flowers long-pediceled; plant of peaty habitats but not aquatic; stigma inconspicuous (corolla longer); fruit a capsule




(Inflorescence Apparently Converted to Bulblets, Tufts of Leaves, etc.)

1. Leaves with flat, broad, net-veined (or dissected) blades

2. Leaves with narrow, sparsely toothed leaflets or further dissected; stem hollow; bulblets produced in the axils of broad-based acuminate bracts or leaves, not transversely segmented

APIACEAE (Cicuta bulbifera)

2. Leaves simple and entire; stem solid; bulblets otherwise

3. Plant a twining vine, leaves alternate and cordate

DIOSCOREACEAE (Dioscorea polystachya)

3. Plant an erect herb, leaves not cordate, opposite or basal and alternate

4. Bulblets unsegmented, in a terminal spike; well developed leaves mostly basal (or alternate)

POLYGONACEAE (Bistorta vivipara)

4. Bulblets transversely segmented, in axils of normal leaves, which are cauline and opposite

MYRSINACEAE (Lysimachia terrestris)

1. Leaves terete or slender and parallel-veined, "grass-like"

5. Bulblets in a ± spherical head or umbel; plants with odor of onion or garlic


5. Bulblets not in a distinct umbel or spherical head; plants without strong odor

6. Leaves terete, septate (with hard cross-partitions, easily seen on dry specimens or felt by gently pinching a leaf and drawing it between the fingers)


6. Leaves flat, neither terete nor septate

7. Stem ± triangular and solid


7. Stem terete, with hollow internodes




(Monocots, with Parallel-Veined Leaves)

1. Plant a climbing or twining vine, in most species with tendrils; flowers unisexual; leaves net-veined

2. Inflorescence an umbel; plants with tendrils; ovary superior; fruit a berry


2. Inflorescence spicate to paniculate; plant without tendrils; ovary inferior; fruit a capsule


1. Plant not a vine and without tendrils; flowers bisexual or unisexual; leaves parallel- or net-veined

3. Inflorescence a spadix, subtended by a spathe which may be broad and hood-like or elongate; leaves in some species compound or net-veined

4. Leaves narrow, sword-like, with ± parallel sides; spathe appearing like a continuation of the leaf-like peduncle (the spadix thus apparently lateral)


4. Leaves expanded; spathe clearly differentiated from peduncle


3. Inflorescence not a spadix (if flowers in a head, this with neither an elongate fleshy axis nor a conspicuous subtending spathe); leaves simple, rarely net-veined (in Smilax ecirrata, Trillium, and some Alismataceae)

5. Perianth much reduced: absent, or composed solely of bristles (these small and stiff or elongate and cottony), or of chaffy or scale-like parts, never conspicuously petaloid

6. Individual flowers subtended by 1 or 2 scales; leaves ± elongate, grass-like, usually with a sheath at the base surrounding the stem; fruit a 1-seeded grain or nutlet (achene)

7. Each fertile flower subtended by a single scale (others may be at base of spikelet); sheaths of leaves closed (margins connate); stems frequently triangular (but 4–several-angled or terete in many species), usually solid; leaves usually 3-ranked (especially in a species with terete hollow stem); stamens with filament attached to end of anther; fruit a definitely 2- or 3-sided (rarely nearly terete) nutlet


7. Each flower subtended by 2 scales (almost opposite each other, one rarely absent); sheaths often open; stems ± terete (sometimes flattened), never triangular; leaves not clearly 3-ranked (basically 2-ranked); stamens with filament attached near middle of anther (or apparently so because of sagittate anthers); fruit usually a grain neither flattened (2-sided) nor triangular


6. Individual flowers subtended by no scales or only by bristles, or with a regular perianth of chaffy scales (or tepals); leaves and fruit various

8. Inflorescence a single, very compact, almost spherical head (terminating an erect scape), less than 12 mm across

9. Surface of head (tips of receptacular bracts) white-woolly; flowers chaffy, not concealed by involucral bracts; roots with abundant conspicuous transverse markings


9. Surface of head (bracts) glabrous; flowers yellow or largely concealed by bracts; roots without transverse markings


8. Inflorescence not a single terminal head and/or exceeding 12 mm

10. Inflorescence composed of separate staminate and pistillate portions, the former consisting of conspicuous stamens, sooner or later withering, leaving only the pistillate portion conspicuous


10. Inflorescence composed of bisexual flowers, without conspicuously separate staminate and pistillate portions

11. Flowers in a branched or umbellate inflorescence, solitary or, more often, clustered into small heads of 2 or more; fruit a 3- to many-seeded capsule


11. Flowers in a single elongate spike or zigzag raceme; fruit indehiscent or a 1–2-seeded follicle

12. Spike (truly a spadix) apparently lateral; fruit of each flower indehiscent


12. Spike or raceme terminal; fruit of each flower consisting of 3 or 6 1–2-seeded follicles

13. Pedicels bractless; carpels 3 or 6, erect and ± adherent to a central axis at maturity; leaves all basal or nearly so, without a terminal pore


13. Pedicels bracted; carpels 3, widely divergent in fruit; leaves mostly cauline, each with a terminal pore


5. Perianth at least in part of ± conspicuous white or colored petals

14. Flowers bilaterally symmetrical

15. Ovary inferior; fertile stamens 1 or 2, united with the pistil; flowers not blue (almost any other color)


15. Ovary superior; fertile stamens 3 or 6, free; flowers blue (except albinos), at least in part

16. Sepals colored like the petals; stamens 6, all fertile; flowers in a dense elongate inflorescence


16. Sepals greenish, unlike the petals; stamens 6, 3 with imperfect anthers; flowers few


14. Flowers regular (radially symmetrical)

17. Sepals and petals of quite different color and/or texture, the former green or brownish

18. Leaves in a single whorl of 3 on the stem


18. Leaves all basal or, if cauline, not in a single whorl of 3

19. Petals yellow; flowers in a single compact head less than 12 mm across


19. Petals blue, purple, white, or pink; flowers in a more open or larger inflorescence

20. Pistils several in each flower, each developing into an achene; stamens 6–many; flowers unisexual or bisexual; petals white or pinkish; leaves often broadly elliptic or sagittate, usually ± net-veined, all basal


20. Pistil 1 in each flower, developing into a capsule; stamens 6; flowers bisexual; petals blue, purple, or deep pink (except in occasional albinos); leaves elongate, clearly parallel-veined, basal and cauline

COMMELINACEAE (Tradescantia)

17. Sepals and petals both colored and petaloid, usually similar in shape (tepals) or the sepals (in Iris) of different size and shape

21. Ovary inferior (flowers bisexual)

22. Stamens 3; leaves equitant


22. Stamens 6; leaves not equitant

23. Ovary only half-inferior, part of it adnate to the perianth, glabrous (at most granular-roughened)

MELANTHIACEAE (Aletris, Anticlea)

23. Ovary clearly inferior

24. Foliage and ovary hairy


24. Foliage and ovary glabrous


21. Ovary superior (or flowers unisexual)

25. Pistils 6, united only at the very base, ripening into follicles; stamens 9; flowers pink, in an umbel terminating a long scape


25. Pistil 1, sometimes the carpels slightly separate near the summit; stamens 3–6; flowers and inflorescence various

26. Stamens 3; tepals 6, yellow; plants creeping on wet shores


26. Stamens and tepals 4 or 6, the latter yellow or not; plants erect, of various habitats

27. Flowers or inflorescences lateral, arising from the axils of alternate cauline leaves or scales

28. Leaves scale-like, mostly brownish or yellowish, those on the much-branched upper portion of the plant subtending short green filiform branches (often mistaken for leaves)


28. Leaves broad, flat, green (scale-like leaves or bracts may be present in addition to normal leaves)

29. Leaves net-veined with long or short (but distinct) petioles; flowers unisexual, in umbels of several to many


29. Leaves parallel-veined, sessile, clasping, or perfoliate at base; flowers bisexual, 1–5 at a node


27. Flowers or inflorescences terminal on scapes or leafy (simple or branched) stems

30. Leaves all withering before plant flowers

ALLIACEAE (Allium burdickii & A. tricoccum)

30. Leaves present at flowering time

31. Leaves all in one or two whorls on the stem


31. Leaves alternate or basal, or if in whorls these more than two or some alternate leaves also present

32. Flowers more than 3.5 cm long

33. Leaves perfoliate

CONVALLARIACEAE (Uvularia grandiflora)

33. Leaves not perfoliate

34. Principal leaves cauline, not crowded toward base of plant


34. Principal leaves basal or nearly so; stem leafless above or with very small bracts

35. Flowers solitary


35. Flowers 2–many

36. Leaves ovate to cordate; flower in a raceme


36. Leaves linear; flowers in an umbel, corymb, or panicle

37. Flowers in an umbel or rather irregular corymb, orange or yellow; leaves soft and herbaceous, not evergreen, without fibrous margins


37. Flowers in a panicle, white or creamy; leaves tough and leathery, evergreen, with curling fibers separating from their margins


32. Flowers less than 3.5 cm long

38. Flowers in a many (7–60 or more) flowered umbel on an unbranched stem or scape; plants with odor of onion or garlic


38. Flowers solitary or in a raceme, panicle, or corymb, on a simple or branched stem (if in a few-flowered umbel, then either the stem branched or forked or flowers less than 7)

39. Plants with principal leaves clearly cauline; basal leaves (at least of current season) absent or at most apparently one

40. Stem forked or branched; perianth over 12 mm long


40. Stem unbranched (above the ground and below the inflorescence); perianth usually less than 12 mm long

41. Ovary with a single style; fruit a berry; inflorescence a raceme (tepals up to 7 mm long) or if a panicle, the tepals less than 3 mm long; leaves broadly lanceolate to ovate


41. Ovary with 3 styles (one on each lobe); fruit a capsule; inflorescence a panicle; tepals ca. 5–13 mm long; leaves very elongate


39. Plants with the principal leaves all basal (at ground level) or nearly so; cauline leaves absent, reduced to bracts, or at most much smaller or fewer than basal leaves

42. Flower solitary

LILIACEAE (Erythronium)

42. Flowers 2 or more in an inflorescence

43. Tepals united for half or more of their length

44. Perianth blue, less than 6 mm long; leaves linear (longest leaves at least 20–40 times as long as wide, up to 8 mm wide); plants bulbous


44. Perianth white, 5–10 mm long when mature; leaves lanceolate to elliptic (longest leaves less than 20 times as long as wide or over 1 cm wide, or both); plants not bulbous

45. Leaves elliptic, the widest 2–6 cm broad; stems up to 35 cm tall, about equaling or shorter than the leaves; flowers nodding, on pedicels longer than the subtending bracts; perianth smooth on outside; fruit a berry


45. Leaves narrowly lanceolate or oblanceolate, the widest less than 2 cm broad; stems over 40 cm tall, much surpassing the leaves; flowers ascending on pedicels shorter than the subtending bracts; perianth ± granular-roughened on the outside; fruit a capsule


43. Tepals completely separate or united at base only

46. Ovary with 3 styles (1 on each lobe) in bisexual or pistillate flowers (or flowers all staminate)


46. Ovary with a single style; flowers bisexual

47. Leaves broad (over 3 cm); perianth yellow; fruit a blue berry


47. Leaves long and narrow (less than 1.5 cm wide); perianth white to blue; fruit a capsule




(Flowers in an Involucrate Head)

1. Flowers on a thick fleshy axis (inflorescence a spadix) subtended by a single large overtopping or enveloping bract (spathe); perianth none or of 4 tepals

2. Leaves narrow, sword-like, with ± parallel sides; spathe appearing like a continuation of the leaf-like peduncle (the spadix thus apparently lateral)


2. Leaves expanded; spathe clearly differentiated from peduncle and terminal


1. Flowers not in a spadix overtopped by a spathe; perianth various

3. Leaves parallel-veined, all basal, and less than 5 mm broad

4. Flowers yellow, mostly concealed by bracts; roots without transverse markings; surface of head (bracts) glabrous


4. Flowers chaffy, not concealed by involucral bracts; roots with abundant conspicuous transverse markings; surface of head white-woolly (tips of receptacular bracts)


3. Leaves net-veined or if parallel-veined then at least some cauline and usually more than 5 mm broad

5. Ovary inferior

6. Leaves opposite (very rarely whorled), toothed or pinnatifid (entire in a very local waif, Succisella); corolla 4-lobed, lilac–purple (sometimes pale); stamens 4, separate


6. Leaves and corolla not combined as above, e.g., leaves alternate and/or entire or corolla 5-lobed and/or not lilac–purple

7. Margins of cauline leaves and inflorescence bracts with stiff spines; corolla of separate petals; calyx present (no pappus); stamens separate

APIACEAE (Eryngium)

7. Margins of cauline leaves and bracts various (spiny in a few species); corolla of united petals; calyx usually none (except in Jasione), but a pappus of scales, awns, or bristles often present; stamens almost always fused in a ring around the style

8. Calyx absent, or represented by hairs, scales, or bristles, mostly irregular in number (mostly not 5), or a ring of tissue; fruit an achene


8. Calyx of 5 lobes present; fruit a many seeded capsule dehiscing by 2 apical valves


5. Ovary superior

9. Leaves alternate, compound; involucral bract 3-foliolate; flowers strongly bilaterally symmetrical, papilionaceous (as in other legumes)

FABACEAE (Trifolium)

9. Leaves opposite, simple; flowers often nearly or quite regular

10. Plant with minty odor; ovary deeply 4-lobed, with 1 style; petals united


10. Plant without minty odor; ovary not lobed, with 2 styles; petals separate

CARYOPHYLLACEAE (Petrorhagia and Dianthus)



(Herbaceous Plants with Unisexual Flowers)

1. Leaves compound

2. Leaves palmately compound (or 3-foliolate)

3. Flowers in umbels

4. Leaves cauline, in a single whorl


4. Leaves alternate and basal

APIACEAE (Sanicula)

3. Flowers in spikes or panicles

5. Margins of leaflets entire; flowers at the base of a prolonged fleshy spadix subtended by a single large bract (spathe)

ARACEAE (Arisaema)

5. Margins of leaflets toothed; flowers on normal herbaceous (but not fleshy) pedicels or axes

6. Leaves all opposite; plant a vine; perianth showy


6. Leaves alternate on upper part of stem; plant erect; perianth minute and inconspicuous


2. Leaves pinnately compound or more than once compound

7. Plant a vine, climbing by tendrils; perianth 4-merous; fruit a large 3-lobed bladdery capsule

SAPINDACEAE (Cardiospermum)

7. Plant erect, without tendrils; perianth 4- or 5-merous; fruit not lobed, an achene, berry, or follicle

8. Flowers in tight ovoid heads or umbels

9. Leaves once pinnately compound; flowers in tight heads; perianth 4-merous

ROSACEAE (Poterium)

9. Leaves 2–3 times compound; flowers pediceled, in umbels; perianth 5-merous


8. Flowers in panicles

10. Leaflets with only 3–9 (–12) mostly rounded or obtuse teeth; perianth absent or of one series of parts; fruit an achene


10. Leaflets sharply and closely toothed throughout; perianth with both calyx and corolla (but these small); fruit a follicle

ROSACEAE (Aruncus)

1. Leaves simple

11. Plant with leaves all basal

12. Flowers in dense spikes (or 1–3 at base in Littorella)


12. Flowers pediceled in panicles


11. Plant with leaves all or mostly cauline

13. Leaves peltate or pubescent with forked/stellate hairs


13. Leaves neither peltate nor with forked/stellate hairs

14. Leaves opposite or whorled

15. Flowers solitary in axils of leaves; perianth none; stamen 1


15. Flowers in axillary or terminal inflorescences

17. Leaves hastate, otherwise unlobed but entire to coarsely or irregularly toothed; pistillate flowers and fruit mostly concealed by a pair of bracts with margins ± united at base


17. Leaves not hastate, in some species deeply lobed, in some closely toothed; pistillate flowers without 2 basal bracts

18. Inflorescence terminal; corolla white or colored

19. Cauline leaves deeply pinnately lobed; style 1; stamens 3–4


19. Cauline leaves unlobed; styles 3–7; stamens 10


18. Inflorescence axillary; corolla none or of reduced scales

20. Leaves entire; inflorescence (spike) shorter than the peduncle

PLANTAGINACEAE (Plantago arenaria)

20. Leaves toothed; inflorescence longer than the peduncle

21. Plant a vine; leaves deeply 3–7-lobed


21. Plant erect, not a vine; leaves unlobed


14. Leaves alternate (at least at upper nodes)

22. Evergreen subshrubs with leathery leaves


22. Herbaceous plants with thin, non-persistent leaves

23. Flowers with 6 petaloid tepals and 6 stamens or 3 carpels (dioecious); inflorescences on long peduncles from the nodes (not terminal); leaves with several prominent longitudinal veins (including midrib)

24. Plant a vine with twining stems (no tendrils); inflorescence a spike, raceme, or panicle; ovary inferior, ripening into a winged capsule


24. Plant erect or a vine with tendrils; inflorescence an umbel; ovary superior, ripening into a berry


23. Flowers either with other numbers of tepals, stamens, and carpels or the inflorescence terminal (on main stem or branches); leaves various but without several prominent long veins

25. Perianth with both calyx and corolla (sometimes very inconspicuous); plants climbing or trailing, with tendrils


25. Perianth absent or of 1 series of parts (tepals); plants erect or prostrate, without tendrils

26. Flowers very small, in axillary clusters [plants monoecious; look for pistillate flowers for keying]

27. Style 1; stamens 4 or 5

28. Flowers in long-peduncled, loose, spreading branched axillary clusters or, if smaller and fewer-flowered, then clusters sessile and leaves entire


28. Flowers in short-peduncled, dense, ± spherical clusters in the axils of the crenate-dentate leaves


27. Styles (or sessile stigmas) 2–3; stamens various

29. Styles 3, branched; bracts in inflorescence well developed and at least 5–10-lobed


29. Styles 2–3, unbranched; bracts in inflorescence unlobed (may be toothed)

AMARANTHACEAE (Amaranthus & Atriplex)

26. Flowers small or not, in chiefly terminal inflorescences (spikes, panicles, or racemes on main stem and/or branches)

30. Tepals petaloid (white to pink); flowers in large open racemes


30. Tepals none or minute, not petaloid (often scarious); inflorescence various

31. Flowers consistently 3-merous (tepals 6, stamens 6, carpels 3); stipules united into a sheath (ocrea) surrounding the stem above each node


31. Flowers not consistently 3-merous (tepals 5 or fewer, stamens usually 5, styles often 2); stipules none




(Herbaceous Dicots with Bisexual Flowers, Perianth in One Series, & Inferior Ovary)

1. Stamens more numerous than the 1–4 perianth lobes or parts

2. Perianth with 1–3 (rarely 4) lobes; stamens 6 or 12


2. Perianth 4-parted; stamens 8 or numerous

3. Leaves pinnately compound; stamens numerous

ROSACEAE (Poterium)

3. Leaves simple; stamens normally 8

SAXIFRAGACEAE (Chrysosplenium)

1. Stamens the same number as or fewer than the perianth lobes or parts, or perianth 5-merous (or both conditions)

4. Leaves all or mostly opposite or whorled

5. Inflorescence a dense terminal cluster of flowers (sessile or nearly so)

6. Leaves apparently whorled; bracts below the inflorescence large and white

CORNACEAE (Cornus canadensis)

6. Leaves clearly opposite; bracts below the inflorescence greenish or inconspicuous

7. Heads subtended by several involucral bracts below a receptacle with sessile flowers


7. Heads not subtended by a distinct involucre, with visible branching structure; flowers sessile but not on a common receptacle


5. Inflorescence of solitary, axillary, or clearly pediceled flowers

8. Leaves compound, in a single whorl


8. Leaves simple or deeply lobed, opposite or in several whorls (rarely the lower alternate in Valeriana)

9. Leaves in whorls


9. Leaves opposite

10. Plant low and densely matted, with linear leaves; perianth 5-merous


10. Plant prostrate or erect, but with broader leaves; perianth 5- or 4-merous

11. Flowers in rather dense terminal inflorescences (at ends of stem and branches); stamens 3 (occasionally 4)


11. Flowers 1–few in axils or solitary at ends of branches; stamens various

12. Styles 2; flowers solitary at ends of branches; plant flowering in May

SAXIFRAGACEAE (Chrysosplenium)

12. Style 1; flowers sessile, axillary; plant flowering in summer

ONAGRACEAE (Ludwigia palustris)

4. Leaves alternate or basal

13. Leaves entire, simple and unlobed; flowers in cymes or few-flowered cymules; style 1


13. Leaves (at least the cauline ones) toothed or crenulate (entire in Bupleurum, with upper leaves perfoliate), often deeply lobed or compound; flowers in umbels, axillary, or ovoid to cylindric heads; styles 2, 3, or 5 (1 in Sanguisorba)

14. Tepals and stamens each 5

15. Styles 5; fruit fleshy, berry-like


15. Styles 2; fruit dry, splitting into 2 achene-like indehiscent parts (mericarps)

16. Leaves simple, with crenate margins


16. Leaves, at least the cauline, compound, dissected, or deeply lobed (simple but entire margined and with the upper perfoliate in Bupleurum)


14. Tepals and stamens each 3 or 4

17. Stamens and tepals 3

HALORAGACEAE (Proserpinaca)

17. Stamens and tepals 4

18. Leaves with conspicuous stipules, pinnately compound and strongly toothed

ROSACEAE (Sanguisorba)

18. Leaves without stipules

go to couplet 11



(Herbaceous Dicots with Bisexual Flowers, Perianth in One Series, & Superior Ovary)

1. Ovaries more than 1 in each flower, the carpels separate at least above the middle of the ovaries

2. Stipules conspicuous; leaves pinnately compound

ROSACEAE (Poterium)

2. Stipules none or leaves simple

3. Ovaries united for most of lower half; leaves simple, unlobed


3. Ovaries distinct; leaves of most species lobed or compound


1. Ovary 1 in each flower (bearing 1 or more styles), the carpels united at least below the styles

4. Leaves bipinnately compound, fruit a legume


4. Leaves simple or compound (but not bipinnate); fruit not a legume

5. Plants with a solitary large (ca. 3–5 cm wide) white flower between a single usually opposite or subopposite pair of long-petioled cauline eccentrically peltate and deeply lobed leaves


5. Plants with more flowers per stem or, if only one, then leaves not as above

6. Stamens more than twice as many as the perianth lobes or parts

7. Leaves tubular, open at apex and hence pitcher-like


7. Leaves flat, of normal structure, simple or compound but not hollow

8. Perianth small and inconspicuous (stamens more showy); leaves compound with definite flat broad leaflets


8. Perianth well developed, showy; leaves simple or dissected into very narrowly linear segments

9. Leaf blades entire, unlobed except for deeply cordate base; plants aquatic


9. Leaf blades deeply lobed or dissected; plants terrestrial

10. Perianth parts 5; leaves pinnately dissected; sap watery


10. Perianth parts 4 or 8; leaves ternately dissected (with watery sap) or otherwise toothed, spiny-margined, or lobed (with milky or colored sap)


6. Stamens only twice as many as the perianth lobes or parts, or fewer

11. Style 1 or none (stigmas may be 2 or more)

12. Stamens more numerous than the perianth divisions

13. Flowers bilaterally symmetrical; perianth colorful (white, yellow, or pink)


13. Flowers regular; perianth dull, greenish

14. Leaves opposite; flowers mostly axillary


14. Leaves alternate or basal; flowers mostly terminal


12. Stamens the same number as or fewer than the perianth lobes or parts

15. Leaves alternate or basal

16. Perianth parts (and stamens) 6, 8, or 9


16. Perianth parts (and usually stamens) 4

17. Leaves simple, entire or with dentate margins

18. Leaves alternate, hairy

ROSACEAE (Alchemilla)

18. Leaves opposite, glabrous

URTICACEAE (Parietaria)

17. Leaves pinnately compound with toothed leaflets

ROSACEAE (Sanguisorba)

15. Leaves opposite

19. Flowers solitary or few in axils of leaves, sessile or nearly so

20. Perianth with 4 teeth or shallow lobes alternating with 4 appendages; style 1, with capitate stigma


20. Perianth with 5 divisions; style none (stigmas 2, sessile)


19. Flowers in terminal inflorescences (on stems and branches)

21. Perianth showy, pink to purple; inflorescences each subtended by a conspicuous petaloid or papery 5-lobed involucre which enlarges as fruit matures


21. Perianth reduced, inconspicuous, whitish or scarious; inflorescences subtended at most by very small bracts

22. Flowers in cymes; perianth glabrous; style none (sessile stigmas 2); filaments separate


22. Flowers in dense heads or spikes; perianth woolly; style 1; filaments united into a tube (simulating a corolla except for its bearing anthers!)


11. Styles 2 or more

23. Flowers embedded in a succulent segmented stem; leaves reduced to tiny opposite scales


23. Flowers not embedded in a succulent stem; leaves not scale-like

24. Leaves opposite or whorled

25. Margins of leaves crenate; stamens normally 8

SAXIFRAGACEAE (Chrysosplenium)

25. Margins of leaves entire; stamens various, but usually not 8

26. Leaves opposite


26. Leaves whorled


24. Leaves alternate

27. Stamens and styles each mostly 10; flowers in distinct simple racemes


27. Stamens and (especially) styles fewer than 10; flowers not in distinct racemes

28. Plant with a ± membranous stipular sheath (ocrea) surrounding the stem above each node


28. Plant lacking stipules of any kind




(Herbaceous Dicots with Bisexual Flowers, Perianth in Two Series, and Ovaries Two or More in Each Flower)

1. Style and/or stigmas united (i.e., 1 in each flower, but style may be branched)

2. Ovaries 2; corolla regular, of united petals; stamens 5; sap in most species milky


2. Ovaries 4 or more; corolla regular or bilaterally symmetrical, of united or separate petals; stamens 2, 4, 5, or numerous; sap not milky

3. Petals separate; ovaries apparently 5 or more; stamens numerous, their filaments connate, at least for much of their length, into a tube around the style; leaves palmately veined (may be deeply lobed)


3. Petals united; ovaries apparently 4; stamens 2, 4, or 5, their filaments not connate (but ± adnate to corolla); leaves mostly pinnately veined

4. Leaves alternate (except at lower nodes in the rare Plagiobothrys); stamens 5; corolla regular (bilaterally symmetrical only in the very bristly Echium); stems not angled (rarely winged) and foliage not aromatic


4. Leaves opposite; stamens 2 or 4; corolla bilaterally symmetrical or in a few genera essentially regular; stems usually 4-angled (“square”) and foliage often aromatic when bruised (“minty” or citrus-like)


1. Style and stigmas separate (1 on each ovary, or scarcely developed)

5. Perianth bilaterally symmetrical

6. Leaves deeply cleft; stamens numerous; perianth with spurs; fruit a follicle (3 per flower)

RANUNCULACEAE (Aconitum and Delphinium)

6. Leaves shallowly lobed; stamens 5; perianth without spurs; fruit a capsule


5. Perianth regular

7. Sepals (or sepal-like bracts) 3

8. Plant aquatic, with peltate (often floating) round or shield-shaped alternate floating leaf blades or palmately dissected opposite submersed leaves


8. Plant terrestrial, with leaves neither peltate nor palmately dissected

9. Petals and usually carpels 3; stamens 3 or 6; leaves cauline, deeply and narrowly pinnate-lobed


9. Petals 5 or more, carpels and stamens numerous; leaves basal, with 3 (–7) broad lobes


7. Sepals 4 or more

10. Leaves peltate, the blades round, often floating, and mostly more than 15 cm broad; flowers mostly over 10 cm broad, with carpels embedded in a top-shaped receptacle


10. Leaves not peltate, the blades (of leaflets, if leaves compound) neither round nor as broad as 15 cm; flowers smaller and carpels not embedded in receptacle

11. Sepals separate to the base; stamens and petals individually falling from the receptacle after anthesis


11. Sepals, petals, and stamens united to form a saucer- or cup-like floral tube (“hypanthium”) at the margin of which the stamens and petals are borne

12. Carpels as many as, or more than, the petals

13. Leaves succulent, simple, entire, estipulate


13. Leaves not succulent, deeply lobed or compound (simple in Dalibarda), toothed, stipulate


12. Carpels fewer than the petals

14. Leaves simple, at most shallowly lobed


14. Leaves clearly compound




(Herbaceous Dicots, with Bisexual Flowers, Perianth in Two Series, and Ovary Inferior)

1. Stamens twice as many as the petals (or approximately so)

2. Style 1 (sometimes very short)

3. Petals spreading; herbaceous plants; fruit a capsule or dry and indehiscent


3. Petals strongly reflexed; creeping evergreen wetland subshrubs; fruit a berry

ERICACEAE (Vaccinium oxycoccos and V. macrocarpon)

2. Styles 2 or more

4. Sepals 2; leaves succulent; styles 3


4. Sepals (4–) 5; leaves not succulent; styles 2


1. Stamens the same number as the petals or corolla lobes, or fewer

5. Petals united

6. Cauline leaves alternate

7. Corolla bilaterally symmetrical


7. Corolla regular

8. Flowers less than 3 mm broad


8. Flowers much larger


6. Cauline leaves opposite or whorled (rarely the lower alternate in Valeriana with pinnate leaves)

9. Leaves whorled


9. Leaves opposite

10. Stipules present (connate around the stem)


10. Stipules absent

11. Flowers sessile in terminal heads

12. Heads subtended by several involucral bracts below a receptacle with sessile flowers


12. Heads not subtended by a distinct involucre, with visible branching structure; flowers sessile but not on a common receptacle


11. Flowers visibly pediceled (even if crowded) or axillary

13. Flowers numerous, in rather dense terminal inflorescences (at ends of stem and branches)


13. Flowers axillary or on paired pedicels on a peduncle

14. Leaves strictly entire, stems erect


14. Leaves shallowly toothed on apical half; stems trailing; flowers on paired pedicels on a peduncle


5. Petals separate

15. Stamens and petals each 2


15. Stamens (fertile) and petals each 4 or 5 (stamens sometimes alternating with staminodia, which may have gland-tipped divisions)

16. Petals 4

17. Principal leaves apparently whorled; flowers in a dense head like terminal cluster subtended by 4 large white bracts

CORNACEAE (Cornus canadensis)

17. Principal leaves alternate; flowers neither in a head-like terminal cluster nor subtended by 4 large white bracts


16. Petals 5

18. Leaves simple; styles 2 or stigmas 4 and sessile; inflorescence various

19. Flowers in panicles, in cymes, or solitary


19. Flowers in umbels


18. Leaves compound; inflorescence an umbel

20. Styles 5; fruit berry-like


20. Styles 2–3; fruit various

21. Leaves alternate or basal; fruit dry, splitting into 2 achene-like indehiscent parts (mericarps)


21. Leaves in a single whorl; fruit berry-like




(Herbaceous Dicots with Bisexual Flowers, Perianth in Two Series, Ovary One and Superior, and Stamens More Numerous than the Petals)

1. Corolla bilaterally symmetrical

2. Sepals all or partly petal-like in appearance or prolonged into a spur

3. Spur none; stamens 6, 7, or 8; leaves entire[11]


3. Spur present on one of the sepals

4. Leaves merely crenate or toothed; stamens 5[12]


4. Leaves palmately cleft; stamens numerous


2. Sepals not petal-like in form or appearance, usually green

5. Sepals 2, separate, usually deciduous early in anthesis; leaves dissected or twice-compound


5. Sepals 4 or more, usually ± connate

6. Lower 2 petals forming a laterally compressed “keel” that encloses the stamens; leaves once-compound (simple only in Crotalaria)


6. Lower petals not forming a keel nor enclosing the stamens

7. Flowers completely 5-merous (sepals and petals 5; stamens 5 or usually 10; pistil long-beaked, the 5 carpels evident in a 5-fid apex and 5 mericarps to the fruit); corolla pink or purple, only slightly bilaterally symmetrical; leaves deeply lobed or cleft or compound (the principal cauline ones opposite and prominently toothed or cleft)


7. Flowers with at least the carpels (often one or more other cycles as well) fewer than 5; corolla and leaves various (carpels 5 only in Dictamnus and sometimes Ruta, with alternate leaves and nearly entire leaflets)

8. Leaves simple, deeply lobed to entire

9. Styles 3 (or more); upper petal larger than the others


9. Style 1; upper petal(s) no larger than the others

10. Sepals and petals each 4; stamens 6


10. Sepals and petals each (4) 5–7; stamens twice as many


8. Leaves compound

11. Flowers in dense terminal spikes, each flower very small with 5 anthers, apparently 1 larger petal, and 4 smaller petals arising from a column of stamens

FABACEAE (Dalea purpurea)

11. Flowers not in dense spikes and not so modified

12. Petals and sepals each 4; fruit a thin-walled or bladdery capsule

13. Plant a vine, climbing by tendrils; capsule 3-lobed, large and bladdery

SAPINDACEAE (Cardiospermum)

13. Plant erect, without tendrils; capsule elongate and unlobed

CLEOMACEAE (Polanisia)

12. Petals and sepals each 5; fruit a legume (splitting on 2 sutures or indehiscent) or a woody capsule

14. Corolla yellow; leaves pinnately compound with terminal leaflet none or represented by a bristle; fruit a legume


14. Corolla pink or purple; leaves pinnately compound with a terminal leaflet; fruit a woody capsule

RUTACEAE (Dictamnus)

1. Corolla regular (radially symmetrical)

15. Leaves tubular, open at apex and hence pitcher-like; style greatly expanded, large and umbrella-shaped


15. Leaves flat or at most succulent, of usual shapes; style not unusually expanded

16. Plants with a solitary large (ca 3–5 cm wide) white flower between a single usually opposite or subopposite long-petioled pair of cauline eccentrically peltate and deeply lobed leaves


16. Plants with more flowers per stem or, if only one, then leaves not as above

17. Sepals 2

18. Leaves lobed, compound, or coarsely toothed, not succulent; sap in most species colored (yellow to orange)


18. Leaves unlobed, entire, succulent; sap watery


17. Sepals 3 or more

19. Stamens more than twice as many as the petals

20. Leaves compound

21. Plant clammy-pubescent; leaves palmately compound with 3 entire leaflets

CLEOMACEAE (Polanisia)

21. Plant glabrous or with a little non-glandular pubescence; leaves twice-compound with numerous sharply toothed leaflets


20. Leaves simple

22. Plant truly aquatic, with all leaves basal, the petioles all arising from a rhizome buried under water (except when stranded)

23. Leaves rounded at apex with deep sinus at base


23. Leaves peltate

24. Leaves circular, large (1 dm or more in diameter); flowers yellow


24. Leaves elliptic, less than 1 dm in their longest dimension, flowers reddish or white


22. Plant terrestrial, with at least some leaves cauline

25. Style 1 (or none, with 3 sessile stigmas)


25. Styles 2 or more, evident

26. Leaves opposite, with translucent dots; petals yellow


26. Leaves alternate, without translucent dots; petals of various colors


19. Stamens twice as many as the petals or fewer

27. Stamens fewer than twice as many as the petals

28. Styles 2–5; leaves opposite or whorled, simple and entire

29. Petals yellow


29. Petals white, pink, or red

30. Stamens 9, in 3 distinct groups of 3 each, with 3 conspicuous glands alternating with the groups


30. Stamens various but neither 9 nor in groups


28. Style 1 or none; leaves usually alternate, simple or compound, entire or toothed

31. Sepals 5 (of which the 2 outer ones may be much reduced); petals 3, minute (shorter than the calyx), reddish


31. Sepals and petals each 4; petals usually ± showy, colors various

32. Leaves palmately compound, with entire leaflets; stamens 6 or more, but not with 2 distinctly shorter; pedicels subtended by bracts


32. Leaves simple or if palmately compound the leaflets coarsely toothed; stamens 6, of which 2 are distinctly shorter; pedicels usually bractless


27. Stamens exactly twice as many as the petals

33. Petals 3

34. Leaves alternate, compound or deeply pinnately lobed


34. Leaves in a single whorl, simple and unlobed


33. Petals 4 or more

35. Sepals and petals each 6 or more


35. Sepals and petals each 4 or 5

36. Leaves compound or deeply divided nearly to base of blade

37. Leaves opposite

38. Leaves uniformly trifoliolate


38. Leaves pinnate, or variously palmately compound or lobed

39. Petals yellow; leaves pinnately compound; plant prostrate and hairy


39. Petals pink to purple or red; leaves palmately compound or lobed; plant ± erect, hairy or not


37. Leaves alternate

40. Styles 5; leaves with 3 obcordate leaflets


40. Style 1; leaves various, but if 3-foliolate, the leaflets not obcordate

41. Leaves palmately compound


41. Leaves pinnately compound or twice pinnatifid

42. Leaves pinnate; fruit a legume (pod splitting on 2 sutures); plants not strongly aromatic


42. Leaves twice pinnatifid; fruit a 4–5-lobed capsule; plants strongly aromatic


36. Leaves simple and entire, toothed, or shallowly lobed

43. Style 1

44. Floral tube (“hypanthium”) present, with petals and sepals borne at its margin; petals white to (usually) pink-purple

45. Anthers opening by terminal pores, very showy (curved, yellow, appearing set at 90° on the filament) and stamens becoming skewed toward one side of the flower


45. Anthers opening by longitudinal slits, not especially showy; stamens not skewed


44. Floral tube none, all parts arising directly from the receptacle; petal color various

46. Sepals of 2 sizes, the 2 outer ones very much narrower and often shorter than the 3 inner ones (appearing as mere appendages on them); petals yellow


46. Sepals all of nearly the same size and shape; petals white, greenish, or pink


43. Styles 2 or more

47. Ovary lobed, with a style on each lobe

48. Leaves not succulent, all or mostly basal, (cauline leaves, if any, few and small or a single pair); lobes of ovary 2


48. Leaves succulent, all or mostly cauline; lobes of ovary 4 or 5


47. Ovary unlobed, the styles all arising together

49. Petals yellow; leaves with translucent dots


49. Petals white to pink or red (never yellow); leaves without translucent dots




(Herbaceous Dicots with Bisexual Flowers, Perianth in Two Series, Ovary One and Superior, Stamens the Same Number as the Petals or Fewer, and Petals Separate)

1. Leaves compound or dissected

2. Flowers solitary on leafless peduncles arising from the ground

3. Corolla bilaterally symmetrical, spurred; petals 5


3. Corolla regular, without spur; petals mostly 8


2. Flowers on leafy stems

4. Leaves dissected or 2–3-times compound; inflorescence open, peduncled

5. Petals and stamens each 6; leaves 2–3-times compound, with flat, broad leaflets

BERBERIDACEAE (Caulophyllum)

5. Petals and stamens each 5; leaves dissected


4. Leaves pinnately compound; inflorescence of nearly sessile and axillary flowers or a dense terminal spike

6. Flowers axillary or supra-axillary and sessile or almost so; corolla yellow; petioles with a conspicuous disc-shaped short-stalked gland; leaves without a terminal leaflet

FABACEAE (Chamaecrista nictitans)

6. Flowers in a dense terminal spike; corolla purple; petioles without a gland; leaves with a terminal leaflet

FABACEAE (Dalea purpurea)

1. Leaves entire or toothed to deeply lobed

7. Leaves opposite or whorled

8. Sepals 2 or 3; petals 2–6

9. Plant aquatic or stranded on wet shores; sepals and petals each of the same number (2 or 3)


9. Plant terrestrial; sepals 2; petals 5 or 6

10. Cauline leaves 2; flowers pedunculate


10. Cauline leaves numerous; flowers essentially sessile


8. Sepals and petals each 4–6 (or more)

11. Leaves deeply palmately lobed


11. Leaves entire or merely toothed

12. Style 1, sometimes very short or the stigma ± sessile

13. Floral tube or disk well developed, with sepals and petals borne at its margin

14. Petals pink, styles elongated, floral tube present; herbaceous


14. Petals greenish or purplish, style essentially absent (stigma ± sessile); ± flat floral disk present; creeping, green-barked low soft-wooded shrub

CELASTRACEAE (Euonymus obovatus)

13. Floral tube or disk none

15. Stamens opposite the petals (i.e., each stamen oriented above the middle of a petal)


15. Stamens alternating with the petals


12. Styles 2–5

16. Flowers completely 5-merous, including 5 styles; stamens with filaments connate at the base around the ovary; ovary 5- (or 10-) locular


16. Flowers with styles usually fewer than 5 (and petals sometimes 4); stamens not connate; ovary with 1 locule

17. Petals yellow; leaves with translucent dots


17. Petals white to pink or red; leaves without translucent dots

18. Petals distinctly separate all the way to the base; stem not 4-angled


18. Petals slightly connate at base; stem sharply 4-angled (even narrowly winged)


7. Leaves alternate or basal

19. Leaves shallowly to deeply palmately lobed

20. Corolla bilaterally symmetrical, spurred; style 1


20. Corolla regular or nearly so, not spurred; styles 2


19. Leaves unlobed or pinnately lobed

21. Styles 2 or more

22. Leaves essentially all basal; flowers white or lavender to violet

23. Leaves with conspicuous stalked glands, flowers white


23. Leaves lacking glands; flowers lavender to violet


22. Leaves cauline; flowers yellow (white in Linum catharticum)


21. Style 1 or none

24. Floral tube well developed and prolonged, with sepals and petals borne at its margin


24. Floral tube none or very little developed

25. Corolla bilaterally symmetrical, saccate or spurred at the base


25. Corolla regular, without a spur

26. Petals and sepals each 4


26. Petals and sepals each 5

27. Leaves pinnately lobed or dissected


27. Leaves entire or merely toothed

28. Flowers solitary, terminal; styles essentially none (stigmas 4, nearly sessile); stamens alternating with cleft, gland-tipped staminodia


28. Flowers in a terminal umbel or raceme; style present; staminodia none

29. Principal leaves all basal; inflorescence a stalked umbel


29. Principal leaves all or partly cauline; inflorescence an axillary or terminal raceme

30. Petals ca. 1 mm long or less; flowers in axillary and terminal racemes; leaves glabrous


30. Petals ca. 3.5–5 mm long; flowers in terminal racemes; leaves finely pubescent

MYRSINACEAE (Lysimachia)



(Herbaceous Dicots with Bisexual Flowers, Perianth in Two Series, Ovary One and Superior, Corolla Regular and Stamens the Same Number as Its Lobes, and Petals United)

1. Leaves all basal

2. Leaves covered with conspicuous stalked glands


2. Leaves without stalked glands

3. Perianth 4-merous; flowers in spikes or heads; corolla scarious


3. Perianth 5-merous; flowers in umbels or panicles; corolla petaloid

4. Fruit a many seeded capsule, flowers umbellate


4. Fruit a one-seeded utricle, flowers in a large panicle


1. Leaves all or mostly cauline

5. Ovary deeply 4-lobed, appearing like 4 separate ovaries [and also keyed as such] but with one style arising deep in the midst of the lobes

6. Leaves opposite; stamens 2 or 4; stems 4-angled (“square”) and foliage aromatic (minty or citrus-like)


6. Leaves alternate (except at lower nodes in the very rare Plagiobothrys); stamens 5; stem not angled (rarely winged) and foliage not aromatic


5. Ovary not conspicuously lobed (may be slightly 4- or 2-lobed or notched at apex, where style arises)

7. Leaves opposite (or whorled), at least below the inflorescence

8. Flowers in dense heads or short spikes; corolla 4-lobed

9. Corolla scarious; leaves linear, entire

PLANTAGINACEAE (Plantago arenaria)

9. Corolla petaloid; leaves lance-elliptic, toothed


8. Flowers in crowded or more open racemes or other inflorescences; corolla lobes 4–7

10. Stamens opposite the corolla lobes (i.e., each stamen arising and oriented above the middle of a lobe) and readily visible


10. Stamens alternating with the corolla lobes (sometimes hidden in a corolla tube or closed corolla)

11. Lobes of corolla 4


11. Lobes of corolla 5

12. Stigmas 3; ovary with 3 locules


12. Stigma 1 (may be 2-lobed); ovary with 2 (or 4 or 5) locules

13. Leaves glabrous; ovary 1-locular; fruit a 2-valved capsule


13. Leaves strongly clammy-pubescent; ovary 2-locular; fruit a berry or a 2-valved capsule

SOLANACEAE (some Leucophysalis and Petunia)

7. Leaves alternate, at least below the inflorescence

14. Blades of leaves deeply lobed, dissected, or compound

15. Plant a twining or trailing vine

16. Corolla deeply funnel-shaped (or even trumpet-shaped)


16. Corolla ± flat (rotate)


15. Plant, whether erect or prostrate, not a vine

17. Anthers forming a cone around the pistil


17. Anthers clearly separate

18. Leaves 3-foliolate


18. Leaves otherwise lobed, compound, or dissected

19. Leaves pinnately compound or pinnately dissected into entire filiform lobes (pectinate); ovary 3-locular; stigmas or style branches 3; capsule 3-valved


19. Leaves not compound: pinnatifid or bipinnatifid, the segments not both entire and filiform; ovary 1-locular; stigmas or style branches 2; capsule 2-valved


14. Blades of leaves entire, toothed, or at most shallowly lobed (or merely cordate)

20. Leaves reduced to small scales; flowers 4-merous


20. Leaves developed; flowers mostly 5-merous

21. Flowers or inflorescences axillary

22. Fruit a 4-seeded capsule; corolla large, funnel-shaped; stigmas clearly 2, separate (except in Ipomoea, where at most 2–3-lobed)


22. Fruit a many-seeded berry or capsule; corolla large and funnel-shaped (in Datura, Petunia) or ± flat (rotate) or bell-shaped; stigma 1


21. Flowers or inflorescences terminal

23. Flowers solitary; corolla over 7 cm long


23. Flowers in clusters; corolla smaller

24. Inflorescence branched (panicle or cyme)

25. Leaves linear to narrowly lanceolate, less than 8 cm long


25. Leaves broad and at least 10 cm long

SOLANACEAE (Nicotiana)

24. Inflorescence simple (spike, raceme, or umbel)

26. Corolla bell-shaped

27. Plant glabrous; flowers less than 3 mm broad, in open racemes; corolla white


27. Plant clammy-pubescent; flowers very much larger, bracted in spike-like racemes; corolla greenish yellow with purple veins

SOLANACEAE (Hyoscyamus)

26. Corolla flat or saucer-shaped

28. Anthers separate, at least some of them on hairy filaments; fruit a capsule


28. Anthers forming a cone around the pistil, on glabrous filaments; fruit a berry




(Herbaceous Dicots with Bisexual Flowers, Perianth in Two Series, Ovary One and Superior, Corolla Either Bilaterally symmetrical or Stamens Fewer than Its Lobes, or Both, and Petals United)

1. Fertile (anther-bearing) stamens 5

2. Ovary deeply 4-lobed; plant strongly bristly-hairy; fruit (1–) 4 nutlets


2. Ovary not lobed; plants glabrous or with dense stellate or clammy pubescence; fruit a capsule

3. Corolla flat or saucer-shaped, white or yellow; filaments (or some of them) hairy


3. Corolla bell-shaped, greenish yellow with purple veins; filaments glabrous

SOLANACEAE (Hyoscyamus)

1. Fertile stamens 2 or 4

4. Corolla with a spur or sac at the base

5. Calyx 2-parted


5. Calyx 5-parted

6. Leaves all basal, glandular-sticky above; flowers solitary on scapes


6. Leaves all or mostly cauline and not sticky (glandular in Chaenorrhinum); flowers not solitary


4. Corolla not prolonged into a spur or sac at the base

7. Cauline leaves all alternate

8. Corolla nearly regular, the lobes equaling or exceeding the tube


8. Corolla bilaterally symmetrical, ± 2-lipped, the lobes (not lips) distinctly shorter than the tube

9. Bracts of inflorescence contrasting with the leaves, cream, yellow, or red at least apically


9. Bracts of inflorescence the same color as the leaves, green or purplish-green

10. Cauline leaves deeply pinnately lobed


10. Cauline leaves unlobed (at most shallowly toothed)


7. Cauline leaves all or mostly opposite or whorled

11. Ovary deeply 4-lobed, appearing like 4 separate ovaries around the base of the single style [and also keyed as such], the fruit (1–) 4 nutlets; plants usually with a 4-angled (“square”) stem and often a minty or citrus-like aroma when bruised


11. Ovary not 4-lobed (at most, somewhat 2-lobed), the fruit a capsule; stem in only a few species 4-angled or with aroma when bruised

12. Fertile stamens 2

13. Flowers in terminal racemes or spikes, or solitary or paired in the axils of the leaves

14. Corolla almost regular, with a 4–5-lobed limb


14. Corolla clearly two lipped

15. Pedicels minutely glandular-pubescent, with a pair of sepal-like bractlets at their summit, subtending the calyx; capsules ovoid or spherical


15. Pedicels smooth and glabrous, without bractlets; leaves not gland-dotted; corolla whitish to purple; capsule distinctly ellipsoid


13. Flowers in axillary racemes or spikes 

16. Corolla almost regular, with a 4-lobed limb


16. Corolla distinctly bilaterally symmetrical, 2-lipped


12. Fertile stamens 4

17. Corolla nearly regular, the lobes about equal

18. Corolla salverform (trumpet-shaped, with a slender tube of almost uniform diameter)

19. Corolla 15–22 mm long; leaves sessile, lance-ovate with few (3–6 per side) short teeth; plant a root-parasite (blackening in drying), considered extinct in Michigan


19. Corolla shorter or leaves more prominently toothed or even lobed; plants (some species) widespread


18. Corolla funnel-shaped or bell-shaped, with a tube broad toward its summit

20. Calyx 5-lobed, bilaterally symmetrical, split nearly to the base on the lower side; plant clammy-pubescent; fruit a drupe, the fleshy outer wall falling away to leave the persistent elongate woody inner wall bearing 2 prominent recurved beaks longer than the body


20. Calyx 4-lobed or if 5-lobed not split beneath and the lobes ± equal; plant glabrous or pubescent but not glandular/clammy; fruit a typical capsule

21. Calyx lobes 4, or short and relatively broad and 0–4; or corolla yellow

22. Corolla bright yellow; calyx tube, pedicels, and/or stems with hairs of uniform or mixed lengths (not of 2 distinct lengths and only rarely completely glabrous)

23. Capsule (like the calyx tube, pedicels, and stem) ± densely pubescent with short uniform eglandular hairs


23. Capsule glabrous; calyx tube, pedicels, and/or stems with viscid or minute gland-tipped hairs


22. Corolla pink to purple (white in albinos); calyx and other parts glabrous (at most scabrous) or with hairs of distinctly different lengths


21. Calyx lobes 5, lanceolate to bristle-like, longer than the calyx tube; corolla pink to purple

24. Stem glabrous to ± hirsute; leaves unlobed, entire, similarly glabrous to hairy


24. Stem rough with stiff retrorse hairs; leaves (at least the uppermost) often with a pair of basal lobes, scabrous above

OROBANCHACEAE (Agalinis auriculata)

17. Corolla strongly bilaterally symmetrical

25. Mature flowers and fruit strongly reflexed, nearly sessile and in remote pairs on opposite sides of a spike-like terminal raceme; calyx with 3 upper teeth bristle-like and 2 lower teeth broadly triangular


25. Mature flowers and fruit not strongly reflexed, and otherwise not as above (long-pediceled, alternate, and/or crowded); calyx with teeth equal or subequal (never bristle-like)

26. Upper lip of corolla apparently absent (the corolla split lengthwise above) or much shorter than the lower lip and (except in Phyla) 4-lobed

27. Flowers in dense short spikes or heads on long axillary peduncles


27. Flowers not in dense heads or spikes


26. Upper lip of corolla well developed, of 2 lobes (or these ± fused into one), often nearly or quite as long as the lower lip

28. Inflorescence terminal and branched (± paniculate); stamens 4 fertile plus 1 staminodium

29. Leaves below the inflorescence distinctly petioled; corolla brownish, less than 12 mm long; staminodium broad (ca. 1–2 mm) and flat at the free apex (mostly adnate to the upper lip), glabrous


29. Leaves below the inflorescence sessile; corolla white to purple-violet, ca. 15–30 (–45) mm long; staminodium slender, elongate (of similar diameter and length as the style), close to lower lip of corolla, bearded at the apex


28. Inflorescence a spike or raceme (no branched stalks), or flowers all axillary; stamens 4 fertile, in most genera with no staminodium (or only a very rudimentary one)

30. Leaves (especially middle and lower ones) deeply pinnately toothed or lobed ca. one-third or more the distance to the midrib

31. Flowers (and fruit) less than 6 mm long


31. Flowers (and usually fruit) over 10 mm long


30. Leaves of main stem toothed or entire but not so deeply pinnately toothed or lobed (uppermost leaves or bracts may have small basal lobes)

32. Sepals separate nearly or quite to the base; flowers in a compact terminal inflorescence


32. Sepals (at least at anthesis) fused ca. one-third or more the length of the calyx; flowers solitary in the leaf axils or in a loose terminal inflorescence

33. Flowers (all or many of them, especially lower ones) in the axils of alternate bracts in a distinct terminal or racemose inflorescence

34. Pedicels about equaling or longer than the calyx and much longer than the minute bracts; calyx glabrous; plants stoloniferous mat forming perennials


34. Pedicels shorter than the calyx and bracts (or none); calyx usually pubescent (except in Euphrasia stricta); plants ± erect annuals


33. Flowers all solitary in the axils of opposite (or whorled) leaves or bracts

35. Lobes less than a third the total length of the calyx, or corolla bright yellow (or both conditions)


35. Lobes ca. half or more the total length of the calyx; corolla blue, purple, white, or cream (rarely yellow)

36. Flowers and fruit on pedicels about equaling or exceeding the calyx; corolla with at least the lower lip deep blue


36. Flowers and fruit sessile or on pedicels distinctly shorter than the calyx; corolla with whitish to pink or magenta ground color (plus dark spots and/or yellow markings)



1In the field, plants are usually readily recognized as being aquatic if one is not misled by a rise in water level to assume that a temporarily inundated plant belongs to a normally aquatic species. In the herbarium, a proper label should record the habitat, but most of the larger true aquatics, even without complete data, can be recognized as such by the delicate structure of submersed stem and leaves, which are often extremely limp and flexible; hence when dry they still convey the impression of having been supported by water. The presence of algae, other aquatic organisms, or marl encrustations is also a handy clue to an underwater source. Rush-like plants (grasses, sedges, rushes) with erect stems extending above the water should not be sought under this part of the key unless they have definite limp aquatic foliage. Aquatics producing only floating leaves, their petioles extending to roots or rhizomes in the substrate, will key here as well as elsewhere in the General Keys on the basis of their floral characters.

2Included in Key C are a few leafless or apparently leafless herbaceous plants which are not parasitic or saprophytic but might be sought here because of decided yellowish (or at least non-green) color of at least some individuals as well as apparently leafless condition at flowering time. Also included are herbaceous plants that flower when leafless. 

3Key D is offered for certain plants that are obviously mature seed-plants (not ferns and their allies) but often produce sterile structures as described rather than flowers; specimens of these species, if they possess flowers, may also be run in the appropriate other portions of the General Keys.

4The plants in Key E are monocots, which usually have floral parts in 3’s (rarely 2’s, never 5’s) and parallel-veined leaves. The few monocots with apparently netted-veined leaves will also run in the alternative lead of this couplet, where all dicots belong, even those with apparently parallel-veined leaves. All plants not covered in keys A (aquatics), B (woody plants), and C & D (plants lacking green color or with inflorescences with bulbils or tufts of leaves) with flat ribbon-like, grass-like or sword-shaped, or ± terete linear-subulate leaves belong here, even if the veins are obscure, unless (1) perianth parts (sepals or petals or both) are present and 5, (2) the perianth is absent or chaffy with the stamens 1 or 4, or (3) the flowers are in an involucrate head (cf. Key F). All plants with rush-like stems and apparently leafless or the leaves bristle-like, 3-angled or involute, belong here. Only 4 non-monocots have flower parts uniformly in sets of 3|Asarum, Floerkea, Proserpinaca, and Rumex.

5All plants not covered in keys A–D with compound, deeply lobed, or toothed leaves belong here, as do all others (even monocots) with distinctly netted-veined leaves, i.e. with some main veins diverging from the midvein rather than all running from base to apex of blade. Also included here are the 3 numbered exceptional “parallel-veined” options excluded (in footnote 4) under the alternative lead (to Key E), but generally recognizable as dicots by having perianth parts in 5’s (commonly), a chaffy (or absent) perianth and 1 or 4 stamens, and/or an involucrate head.

6Each stamen and pistil in Euphorbia is anatomically a very much reduced single flower, as evidenced by the stalk of the ovary and a joint or swelling on the stalk of a stamen, marking the junction of a pedicel and filament.

7If perfect flowers are also found on a plant, try also the alternative lead. Some plants with flowers in which either the stamens or the pistils mature distinctly earlier than the other are included here as well as under perfect flowers, but users should be cautious on this point.

8Several genera and families are included for convenience here that technically have both corolla and calyx but in which one of these series either is tiny or vestigial and hence usually overlooked or falls off very early in anthesis.

9A few plants are included here in which the ovary position is so obscure in a technically perigynous flower as to be easily misinterpreted as inferior.

10Various plants might be sought here, including species of Poa and Festuca normally with some bulblets and others with deformed (diseased?) inflorescences.

11The flowers in Polygala superficially resemble those of the Fabaceae (“papilionaceous”) but the perianth parts are not parallel. Of the 5 sepals, the 2 lateral ones are large and petaloid (“wings”); the petals are 3, the lower one forming a “keel” (usually with a fringe or appendage near the end).

12The flowers in Impatiens include 3 sepals, of which the lower one is large, petaloid, sac-like, and slender-spurred; the petals are apparently 3, each of the 2 lateral ones with a lobe.

13Our genera of Lamiaceae having an ovary not deeply 4-lobed and which therefore will key here are Ajuga, Teucrium, and Trichostema.