Flora of the Southeastern United States
2022 Edition

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Key to Eragrostis

1 Plants cespitose or rhizomatous perennials, with innovations near the base, and with or without buds in the basal sheaths.
..2 Palea with a broadened wing or tooth on each side near its base that often projects beyond the lemma
..2 Palea lacking a broadened wing or tooth near its base
....3 Plants with short, knotty, thick rhizomes; florets articulating whole
....3 Plants without short or thick rhizomes; florets usually disarticulating.
......4 Caryopsis with a deep to shallow groove along the adaxial surface.
........5 Caryopsis dorsoventrally compressed, flattened parallel to the side of the embryo, translucent, light brownish
........5 Caryopsis laterally compressed, flattened on the side perpendicular to the embryo, or cylindric, opaque (rarely translucent), usually reddish brown.
..........6 Lateral veins of the lemmas conspicuous, often greenish, the lemmas strongly keeled
..........6 Lateral veins of the lemmas inconspicuous and hardly evident, the lemmas sometimes weakly keeled.
............ 7 Lemmas 1.2-1.8 mm long; culms 30-70 cm tall
............ 7 Lemmas 1.6-3.0 mm long; culms (30-) 40-110 (-120) cm tall.
............ ..8 Spikelets 2-6-flowered, greenish with purple tinges; leaf blades 3-8 (-11) mm wide, 25-60 cm long; sheaths often densely papillose-hirsute
............ ..8 Spikelets (3-) 5-12-flowered, olive green to lead gray; leaf blades 1-3.8 mm wide, (4-) 10-35 cm long; sheaths never papillose-hirsute
......4 Caryopsis not grooved on the adaxial surface.
............ ....9 Stamens 3.
............ ......10 Spikelets 4-8.2 (-10) mm long
............ ......10 Spikelets 2-4.5 (-5) mm long.
............ ........11 Leaf blades 25-60 cm long, 3-8 (-11) mm wide; lemmas 1.6-2.4 mm long; spikelets 1.0-1.7 mm wide
............ ........11 Leaf blades (4-) 8-22 cm long, 1-3.5 mm wide; lemmas 1.2-1.8 mm long; spikelets 0.5-1.0 (-1.3) mm wide
............ ....9 Stamens 2.
............ ..........12 Panicle 15-45 cm wide, open, diffuse, broadly ovate to obovate in outline, the panicle branches capillary; pedicels 0.5-35 (-50) mm long, longer than or shorter than the spikelets.
............ ............ 13 Spikelets with widely spreading pedicels, the lower pedicels all generally longer than the spikelets; disarticulation of the lemmas only, the paleas persistent
............ ............ 13 Spikelets with appressed pedicels, lower pedicels of each branch shorter than the spikelets; disarticulation usually of the whole floret
............ ..........12 Panicle (1-) 2-17 (-20) cm wide, contracted to open, narrowly ovate to oblong in outline, the panicle branches stiffly spreading; pedicels (0-) 0.3-6 mm long, always shorter than the spikelets.
............ ............ ..14 Spikelets 0.7-2.4 mm wide; glumes 0.3-2.2 mm long; lemma 1.5-2.5 mm long, the apex acute (sometimes acuminate)
............ ............ ..14 Spikelets 2.4-5 mm wide; glumes 1.4-4 mm long; lemma 2-6 mm long, the apex acuminate to attenuate
1 Plants cespitose, geniculate or mat-forming annuals, lacking innovations or buds in the lower sheaths.
............ ............ ....15 Paleas prominently ciliate-pectinate on the keels, the hairs 0.1-0.8 mm long.
............ ............ ......16 Panicles contracted, narrow, spike-like, usually <1.5 cm wide
............ ............ ......16 Panicles open, cylindrical to narrowly ovate, usually 1-8 cm wide.
............ ............ ........17 Spikelets (1.0-) 1.5-3.5 mm long, 0.9-1.4 mm wide, 4-12-flowered; lemmas 0.7-1.1 mm long, membranous, the apex truncate to obtuse
............ ............ ........17 Spikelets 5-12 (-18) mm long, 1.4-2.4 mm wide, 12-42-flowered; lemmas (1.3-) 1.5-2.0 mm long, chartaceous, the apex acute
............ ............ ....15 Paleas smooth to scaberulous on the keels, the hairs (if present) <0.1 mm long.
............ ............ ..........18 Plants extensively stoloniferous, creeping and forming flat mats; inflorescences 1-3.5 cm long; culms (2-) 5-12 (-20) cm tall on the erect portions.
............ ............ ............ 19 Hermaphroditic; spikelets bisexual; anthers 2, each 0.2-0.3 mm long
............ ............ ............ 19 Dioecious; spikelets unisexual; anthers 3, each 1.4-2.2 mm long
............ ............ ..........18 Plants not stoloniferous (sometimes creeping and forming flat mats); inflorescences 3-55 cm long; culms (2-) 6-130 cm tall.
............ ............ ............ ..20 Ligules membranous, glabrous
............ ............ ............ ..20 Ligules ciliate, with a row of tiny white hairs.
............ ............ ............ ....21 Caryopsis with a deep to shallow groove along the adaxial surface.
............ ............ ............ ......22 Spikelets (4-) 5-10 (-11) mm long, 5-11 (-15)-flowered; pedicels ascending, somewhat appressed along the branches.
............ ............ ............ ........23 Spikelets ovate to oblong in outline, >1.4 mm wide; lower glume 1.2-2.3 mm long
............ ............ ............ ........23 Spikelets linear to linear-lanceolate, <1.5 mm wide; lower glume 0.7-1.7 mm long
............ ............ ............ ......22 Spikelets (1.4-) 2-5 mm long, 2-6 (-7)-flowered; pedicels erect, spreading along the branches.
............ ............ ............ ..........24 Panicle 10-45 (-55) cm long, 2/3 or more the height of the plant; pedicels (4-) 5-25 mm long; glandular pits absent below the nodes, branches, and rachis
............ ............ ............ ..........24 Panicle 4-20 cm long, < ½ the height of the plant; pedicels 1.5-5 mm long; glandular pits often present below the nodes, branches, and rachis
............ ............ ............ ....21 Caryopsis not grooved on the adaxial surface.
............ ............ ............ ............ 25 Plants with glandular pits or bands on the culm below the nodes, on the veins of the sheath, on the margins and veins of the blade, on the rachis, on the inflorescence branches and pedicels, and/or on the midveins of the lemma and palea.
............ ............ ............ ............ ..26 Spikelets (1.7-) 2-4 mm long, 3-6-flowered
............ ............ ............ ............ ..26 Spikelets (2-) 3.5-20 mm long, (3-) 5-40-flowered.
............ ............ ............ ............ ....27 Spikelets 0.6-1.3 mm wide; pedicels 1-10 mm long, flexuous and delicate, appressed or spreading
............ ............ ............ ............ ....27 Spikelets 1.1-4 mm wide; pedicels 0.2-4 mm long, straight and rigid, mostly spreading.
............ ............ ............ ............ ......28 Spikelets 6-20 mm long, 2-4 mm wide, 10-40-flowered; lemmas 2-2.8 mm long, with 1-3 crateriform glands along the keel; disarticulation of the entire florets from the persistent rachilla; anthers yellow
............ ............ ............ ............ ......28 Spikelets 4-7 (-11) mm long, 1.1-2.2 mm wide, 7-12 (-20)-flowered; lemmas 1.4-1.8 mm long, rarely with 1-2 crateriform glands along the keel; disarticulation of the lemmas only, the palea and rachilla usually persistent; anthers reddish-brown.
............ ............ ............ ............ ........29 Inflorescence with glandular areas of spots or rings on the rachis below the panicle branch bases, the glands often shiny or yellowish; stamens 3; blade margins lacking crateriform glands
............ ............ ............ ............ ........29 Inflorescence sometimes with glandular areas of spots or crateriform pits on the rachis below the panicle branch bases, the glands usually dull and greenish-gray to straw-colored; stamens 2; blade margins sometimes with crateriform glands
............ ............ ............ ............ 25 Plants lacking glandular pits or bands on the culm below the nodes, on the veins of the sheath, on the margins and veins of the blade, on the rachis, on the inflorescence branches and pedicels, and/or on the midveins of the lemma and palea.
............ ............ ............ ............ ..........30 Spikelets (1.6-) 2-4 mm wide, 12-42-flowered; disarticulation of entire florets from a persistent rachilla
............ ............ ............ ............ ..........30 Spikelets 0.6-2.5 mm wide, 3-22-flowered; disarticulation of the lemmas only, the paleas usually persistent (or deciduous), the rachilla persistent.
............ ............ ............ ............ ............ 31 Spikelets 3-6-flowered
............ ............ ............ ............ ............ 31 Spikelets (3-) 5-42-flowered.
............ ............ ............ ............ ............ ..32 Lemmas with conspicuous lateral veins, these usually greenish; grains 0.3-0.6 mm long, ovoid, subglobose, or obovoid.
............ ............ ............ ............ ............ ....33 Spikelets 5-12 (-18) mm long, with 12-42 florets; primary branches 6-10 per culm; lemmas 1.3-2.0 mm long; anthers 3
............ ............ ............ ............ ............ ....33 Spikelets 2-4.6 mm long, with 5-15 florets; primary branches (12-) 15-20 per culm; lemmas 1.0-1.3 mm long; anthers 2
............ ............ ............ ............ ............ ..32 Lemmas with inconspicuous or moderately conspicuous lateral veins, these usually not greenish; grains 0.5-1.1 mm long, pear-shaped, obovoid, or prism-shaped.
............ ............ ............ ............ ............ ......34 First glume 0.3-0.6 (-0.8) mm long, <0.5× as long as the lowest lemma; spikelets 0.6-1.3 mm wide; panicle branches usually whorled at the lowest 2 nodes
............ ............ ............ ............ ............ ......34 First glume 0.5-1.5 mm long, >0.5× as long as the lowest lemma; spikelets 1.2-2.5 mm wide; panicle branches solitary or paired at the 2 lowest nodes.
............ ............ ............ ............ ............ ........35 Anthers 0.5-0.7 mm long; [endemic to s. FL]
............ ............ ............ ............ ............ ........35 Anthers 0.2-0.4 mm long; [collectively widespread in our area]
............ ............ ............ ............ ............ ..........36 Pedicels widely spreading
............ ............ ............ ............ ............ ..........36 Pedicels appressed or rarely diverging up to 20 degrees from the branches