Andropogon, Bothriochloa, Dichanthium, Schizachyrium

Schizachyrium is similar to Andropogon but differs by having the ultimate inflorescence axes (racemes or rames of some authors) single rather than paired. Also similar, Bothriochloa pertusa has a conspicuous pit on each spikelet. Dichanthium is under 1 m tall, has the rames clustered at the top of the plant, and often has awns > 16 mm long (which is rare in Andropogon).

1. Spikelets with a conspicuous gland or pit (visible with a hand lens) on the lower glume…Bothriochloa pertusa (Spikelets 3-4 mm long; awn 10-17 mm long)

1. Spikelets glandless…2

2. Ultimate branches of the inflorescence (rames) single, zig-zag...10

2. Rames paired...3

3. Plants < 1 m tall; rames confined to top, awns often > 20 mm long...Dichanthium

3. Plants usually > 1 m tall (with exceptions; see "6" below); rames not confined to the top; awns usually < 16 mm long...4

4. Peduncles exposed, curved or drooping; ultimate inflorescence branches (rames) < 2.1 cm long…A. brachystachyus

4. Peduncles hidden, or exposed and straight; rames of variable lengths, usually (but not always) exceeding 2.1 cm long...5

5. Sessile spikelets usually (4.5)5-8.4 mm long. Pedicellate spikelets well developed…A. ternarius (plants usually in dry pine woods, with few [easily counted] inflorescence units [vs. crowded and numerous in A. floridanus], rames 3-6 cm, on long exposed straight peduncles; anthers 3; awns to 25 mm)

5. Sessile spikelets usually < 4.5 mm long. Pedicellate spikelets absent or vestigial…6

6. Plants < 1 m tall...7

6. Plants > 1 m tall (there may be small individuals in a population generally > 1 m tall)...8

7. Inflorescence with expanded sheath(s) (inflated and out of proportion to the small size of the plant). Leaf blades and sheaths usually glabrous. Rames 2.8-4.2 cm long, usually exserted on peduncles 5-31 mm long. Ligule 0.3-1.5 mm...A. gyrans

7. Inflorescence sheath not expanded; leaf blades and sheaths usually pubescent. Rames 1.8-2.6 cm long, usually included or the peduncle < 4 mm...A. longiberbis

8. Peduncles often > 14 cm. Inflorescence branches (rames, racemes) 2.5-3.7 cm long. Usually in scrub. Inflorescence units numerous and crowded...A. floridanus

8. Peduncles usually < 14 cm. Rames 1.7-2.8 cm long...9

9. Inflorescence highly branched and dense. Ligules 0.6-2.2 mm, ciliate. Sheaths usually scabrous, < 2 mm wide.....A. glomeratus

9. Inflorescence usually diffuse, not a dense mass at the top of the plant. Ligules 0.1-1 mm, membranous to sometimes ciliate. Sheaths usually smooth, > 2 mm wide...A. virginicus

10. Lower glume pubescent or glabrous. Upper glume cleft for > half its length. Awn on sessile spikelet 15-25 mm….Schizachyrium sanguineum

10. Lower glume glabrous. Upper glume cleft for< half its length; awn on sessile spikelet < 17 mm...11

11. Awns on pedicellate spikelet absent-4 mm. Blade 1.5-9 mm…Schizachyrium scoparium

11. Awns on pedicellate spikelet to 1 mm. Blade 1-6 mm wide…S. rhizomatum (syn. of S. scoparium in Wunderlin)