The total number of leaves (i.e., nodes) on a culm is often a useful character in distinguishing species; care must be taken to include the often shriveled leaf at the lowest node. Our species are quite distinct, with very few hybrids apparently collected in Michigan. The range of variation in any one “key character” often meets or slightly overlaps that of another species, so that a plant which does not run well under one half of a couplet in the key should be sought under the other half, where it may better fit the descriptive statements. As construed here, Elymus includes Hystrix and some species treated in Agropyron in Michigan Flora, but the stout species with broad, lanceolate glumes are placed in Leymus. Species with long-creeping rhizomes (E. lanceolatus and E. repens) are sometimes segregated as Elytrigia.
In addition to the species below, Thinopyrum ponticum (Podp.) Barkworth & D. R. Dewey (Elymus elongatus, Agropyron elongatum) is established along roads in southern Ontario and may eventually occur as a wild plant in Michigan. It would key to couplet 15 in the group key, and is a tall clump-forming species with stiff, truncate glumes and an open spike of arcuate spikelets. A collection in BLH (under Agropyron elongatum) from a fly ash dump in Monroe Co. has the note: "planted by hydroseeding techniques... in the summer of 1985."
1. Spikelets clearly 1 at each node (or most nodes) of the rachis; glumes not more than 2.
2. Lemmas densely hairy; leaves with narrow (rarely as much as 4.5 mm wide) often involute blades, the whole plant usually strongly glaucous.
2. Lemmas glabrous (rarely slightly pubescent), smooth or scabrous; leaves various.
3. Anthers (2.7–) 3–5 (–6.1) mm long; rachilla often not readily disarticulating (florets not easily dislodged on dry specimens except over-ripe ones, empty glumes seldom if ever present); culms from elongate rhizomes.
3. Anthers 1–2.2 (–2.4) mm long; rachilla readily disarticulating between the florets when mature (on dry specimens, the florets very easily dislodged and empty glumes often remaining on older plants); culms cespitose, rhizomes absent.
1. Spikelets mostly 2–3 at each node of the rachis (if this arrangement is obscured by reduction of some spikelets and/or their asymmetric position, the basic structure is still evident by the presence of a total of 4–6 awn-like or narrow glumes subtending the entire group of spikelets like an involucre—side by side rather than opposite each other on the two sides of each spikelet).
4. Glumes absent or vestigial, or, if present, slenderly awn-like their entire length and at least one much shorter than the others at a node; spikelets horizontally spreading at maturity (± ascending when young), well separated, clearly revealing the entire rachis.
4. Glumes present, awn-like to lanceolate, of about equal length; spikelets ascending at maturity, usually concealing much of the rachis.
5. Larger paleas (lowest in each spikelet) 8.6–12.7 (–14) mm long; awns of lemmas usually widely spreading to recurved at maturity.
6. Body of glume about twice as long as its awn, or longer; awns of lemmas usually straight at maturity; spike curved to erect.
go to couplet 10
6. Body of glume about equaling its awn, or shorter; awns of lemmas ± curved at maturity (straight when young); spike curved to strongly nodding.
7. Leaves 5–8 on a culm, the broadest blades rarely as much as 15 (–17) mm wide, glabrous above.
7. Leaves 10–12 on a culm, the broadest blades (14–) 15–19 mm wide, finely hairy above.
5. Larger paleas 5.5–8.5 (–9) mm long; awns of lemmas mostly straight.
8. Glumes, at least the broadest, 1–1.7 (–2) mm wide, clearly expanded and flattened above the base.
9. Spikelets spreading to form a spike 2.5–5 cm wide (measured awn tip to awn tip, pressed); longer glume awns 12–25 mm long.
9. Spikelets ascending to form a spike 1–2.2 (–2.5) cm broad; longer glume awns less than 12 mm long.
10. Base of glumes not conspicuously bowed out, but flattened, hardened for less than 1 mm; glumes not thickened above the base on inner face, with very narrow, thin, translucent margins, often slightly overlapping; culm leaves 5–6; largest palea 7.5–10.5 (–12) mm long.
10. Base of glumes ± bowed out, terete and hard for 1 mm or more; glumes also thickened, pale, and hardened on inner face for about the basal half or more, with firm margins, not at all overlapping; culm leaves (6–) 7–10; largest palea 6.8–8.5 (–9) mm long.
8. Glumes less than 1 mm wide, scarcely if at all widened above the base.
11. Palea of lowest floret in spikelet (6.5–) 7–8.5 mm long; leaves ca. (8–) 9–10, glabrous.
11. Palea 5.5–6.7 (–7) mm long; leaves (5–) 6–7, the sheaths and upper surface of blades ± finely villous.