1. Lateral awns < 12 mm long, < half as long and half as thick as central awn (this to 30 mm long)…A. patula

1. Lateral awns 10 or more mm, > half the length of the central awn…2

2. Inflorescence a dense foxtail > 15 mm wide (excluding awns) wide…A. spiciformis

2. Inflorescence otherwise…3

3. Wetland grass with well developed scaly rhizome; upper glume with awn > (3)-7 mm…A. rhizomophora (basal sheath shredding) (central awn 15-30 mm long, horizontal to reflexed; lateral awn 13-20 mm)

3. Wetland or dry habitat grass without strongly developed rhizome; upper glume with no awn or with awn < 3 mm long…4

4. Leaf blades predominantly flat toward the base of the plant…5

4. Leaf blades involute…6

5. Leaf blades curled; lower glume < 9 mm long; ligule < 0.1 mm long; central awn 8-25 mm…A. purpurascens

5. Leaf blades usually not curled; lower glume > 9 mm long; ligule 0.2 mm long; central awn 15-40 mm long…A palustris

6. Awns contorted (also true in A. purpurascens var. tenuispica with flat leaves and equal glumes); glumes unequal; callus usually > 1 mm long; leaf collars glabrous; awns nearly equal…A. gyrans

6. Awns not contorted; glumes nearly equal; callus usually 0.4-0.6 mm; leaf collars pubescent; lateral awns a little shorter than central awn…A. stricta