Eragrostis

1. Plants prostrate basally, rooting at lower nodes; nodes of culm bearded (very rarely glabrate).

E. hypnoides

1. Plants ± erect or spreading from the base, not rooting at the nodes; nodes of culm glabrous.

2. Margins (often inrolled) of leaves and also (usually at least sparsely) pedicels and keels of lemmas and glumes ± glandular-warty.

3. Well-developed spikelets (2.2–) 2.5–3.5 (–4) mm wide; larger glume 1.7–2.5 mm long; sheaths essentially glabrous except at summit.

E. cilianensis

3. Well-developed spikelets 1.5–2 (–2.2) mm wide; larger glume 1–1.5 (–1.8) mm long; sheaths sparsely pilose.

E. minor

2. Margins of leaves, pedicels, and keels of lemmas and glumes not glandular-warty.

4. Spikelets reddish to purplish (except in E. curvula); plants perennial, with hard knotty base; lowest panicle branches usually with a long-pilose white to yellowish or red pulvinus in the axil.

5. Spikelets appressed, longer than their pedicels, dull gray; widest leaves 1–3 mm wide, involute, especially above the middle.

E. curvula

5. Spikelets spreading, mostly shorter than their pedicels, reddish-purple tinged; widest leaves 3–8 mm wide, ± flat.

6. Larger glumes 1.4–2.3 mm long; lower panicle branches reflexed at maturity.

E. spectabilis

6. Larger glumes 2.3–4.5 mm long; lower panicle branches ascending at maturity.

E. trichodes

4. Spikelets greenish gray to dark lead-colored (occasionally with purplish flush besides); plants annual, with relatively soft base; lowest panicle branches with pulvinus glabrous to sparsely pilose (or obscure or absent).

7. Larger spikelets mostly 6–11 (–15)-flowered, usually on ± appressed pedicels (though panicle branches may be widely spreading); lowest lemma ca. 1.4–2 mm long; lateral nerves of lemma distinct (in E. pectinacea).

8. Lateral nerves of lemma distinct, at least on lower half; larger mature spikelets (1.3–) 1.5–2 mm wide; axils of panicle glabrous or rarely the lowermost with a few hairs; panicle branches usually alternate or subopposite at lowest two nodes of inflorescence.

E. pectinacea

8. Lateral nerves of lemma usually obscure; larger mature spikelets ca. 1–1.4 mm wide; axils of lower primary branches of panicle sparsely pilose; panicle branches whorled or clustered at one of the two lowest nodes of inflorescence.

E. pilosa (in part)

7. Larger spikelets mostly 2–4 (–6)-flowered, on spreading pedicels; lowest lemma ca. 1.2–1.4 (–1.6 or very rarely 1.9) mm long; lateral nerves of lemma obscure.

9. Sheaths pilose; grain with a groove the length of one edge; length of culm below lowest branch of terminal panicle less than the height of the panicle.

E. capillaris

9. Sheaths essentially glabrous except at summit; grain not grooved; length of culm below lowest branch of terminal panicle usually more than the panicle.

10. Axils glabrous; tip of second glume ± opposite tip of lowest lemma.

E. frankii

10. Axils of at least the lower primary branches of panicle sparsely long-pilose; tip of second glume usually much shorter than the lowest lemma (across from it).

E. pilosa (in part)

All species found in Eragrostis

Eragrostis capillarisLACE GRASS 
Eragrostis cilianensisSTINK GRASS 
Eragrostis curvulaWEEPING LOVE GRASS 
Eragrostis frankiiSANDBAR LOVE GRASS 
Eragrostis hypnoidesCREEPING LOVE GRASS 
Eragrostis minorLOW LOVE GRASS 
Eragrostis pectinaceaLOVE GRASS 
Eragrostis pilosaSMALL LOVE GRASS 
Eragrostis spectabilisTUMBLE GRASS, PURPLE LOVE GRASS 
Eragrostis trichodesLARGE PURPLE LOVE GRASS 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 17, 2017. http://www.michiganflora.net/genus.aspx?id=Eragrostis.