1 Spikelets pedicellate; if awns present, then arising from just below the lemma apices; lemma apices bifid or not; plants usually perennial, rarely winter annuals.

  2 Spikelets 5-9.5 mm long; second lemma with an awn 3.5-7 mm long

  2 Spikelets 1.5-5 (-5.2) mm long; second lemma awnless, or infrequently with an awn up to 1 mm long (S. nitida) or 3.5-4 mm long (S. filiformis, S. ×pallens), but otherwise awnless.

    3 Lower leaf blades usually involute, mostly (10-) 15-45 cm long, < 2 mm wide

    3 Lower leaf blades flat, mostly < 10 cm long (8-18 cm long in S. longiflora), 2-10 mm wide.

      4 First glume 1/3-2/3 as wide as the second glume; second lemma strongly scabrous

      4 First glume ≤ ⅓ as wide as the second glume; second lemma smooth to slightly scabrous (scabridulous).

        5 First (proximal) lemma with an awn up to 3.5 mm long; distal lemma with awns 0.1-4 mm long

        5 Both first (proximal) and distal lemma unawned.

          6 Spikelets 4-5.2 mm long; panicles nodding, not spikelike; spikelets loosely arranged

          6 Spikelets 2.1-4 mm long; panicles nodding or erect, spikelike or not spikelike; spikelets loosely or densely arranged.

             7 Panicle open; second glume 3-6× as long as wide, acute at the tip; lowermost rachilla internode 0.8-1.0 mm long

             7 Panicle densely cylindrical; second glume 2-3× as long as wide, rounded or truncate at the tip; lowermost rachilla internode 0.5-0.7 mm long

1 Awns of the lemmas 1 mm long, essentially a minute prolonged extension of the lemma midvein; lemma apices acute

1 Awns of the lemmas 2-8 mm long (therefore conspicuous and not merely a minute midvein extension), bent or geniculate and often basally-twisted and exceeding lemma apices; lemma apices bifid or bicuspidate.

  2 Lower and upper glumes unequal, the lower glume shorter than the upper glume (sometimes only 0.5-1.0 mm shorter as in Trisetum aureum, but otherwise conspicuously shorter), 2.0-5.5 mm long (lower glume), 2.5-7 mm long (upper glume); lemma awns arising from the upper 1/3 of the lemmas; plants annual and without sterile shoots OR perennial with both fertile and sterile shoots; [widespread]

    3 Spikelets 2.5-3.5 mm long; lemma awns 2-6 mm long; plants annuals, without sterile shoots

    3 Spikelets 4-8 mm long; lemma awns 3-9 mm long; plants perennial, with both fertile and sterile shoots.

      4 Panicles usually glistening yellowish-brown; spikelets usually with 2 florets (sometimes 3); panicles 5-20 cm long; leaves evenly distributed; ligules 0.5-1(2) mm, obtuse, lacerate, sometimes ciliolate; plants sometimes with rhizomes to 7 cm long; [occurring sporadically in disturbed sites]

      4 Panicles usually silvery-shiny; spikelets usually with 3 florets (sometimes 2 or 4); panicles (5)20-30(50) cm long; leaves mostly basal or evenly distributed; ligules 0.5-4 mm, truncate or rounded; plants not rhizomatous; [cool, moist northern sites, rare and disjunct in high elevation areas s. to VA]