1. Panicle branches tightly entangled for most of their length, separable only with difficulty and forming a cylindrical, spikelike inflorescence, the individual branches visibly distinct only at the tip | C. berroi |
1. Panicle branches sometimes appressed to each other but easily separable, inflorescences evidently composed of multiple spikelike branches borne in 1-several whorls. | → 2 |
2. Panicles with 1-3 branches. | → 3 |
3. Lowest (bisexual) lemmas usually glabrous or scabrous, occasionally with a few scattered hairs on the margins. | → 4 |
4. Lemma of the first sterile floret in each spikelet entire; panicle branches 5-11 cm long, with about 10 spikelets per cm | C. ventricosa |
4. Lemma of the first sterile floret in each spikelet bilobed for 1/3– 1/2 of its length; panicle branches 4-17 cm long, with 3-7 spikelets per cm on the distal portion | C. divaricata |
3. Lowest (bisexual) lemmas conspicuously hairy on the margins and keels. | → 5 |
5. Lemma of the lowest (bisexual) floret in each spikelet 1.8-2.8 mm long | C. ciliata |
5. Lemma of the lowest (bisexual) floret in each spikelet 2.7-4.2 mm long | C. canterae |
2. Panicles with 4 or more branches. | → 6 |
6. Spikelets with 3 or more florets (the third often concealed), the lowest (first) floret bisexual, the remainder sterile or staminate, the terminal floret sometimes represented only by a clavate rachilla segment. | → 7 |
7. Second sterile florets ovoid to subspherical, strongly inflated; first sterile florets 0.9-1.3 mm long | C. barbata |
7. Second sterile florets widened or not distally, not inflated or inflated only near the apices; first sterile florets 1-3.5 mm long. | → 8 |
8. All sterile or staminate florets awned. | → 9 |
9. Culms to 300 cm tall; panicle branches averaging 10 spikelets per cm; spikelets tawny | C. gayana |
9. Culms 30-50 cm tall; panicle branches averaging 6 spikelets per cm; spikelets dark brown to black | C. truncata |
8. At least 1 of the sterile or staminate florets in each spikelet unawned. | → 10 |
10. Spikelets barely imbricate, averaging 5-7 per cm; plants annual or short-lived perennials | C. pilosa |
10. Spikelets strongly imbricate, averaging 10-14 per cm; plants perennial or annual. | → 11 |
11. Margins of the lowest lemma in each spikelet scabrous, glabrous, or appressed pubescent | C. gayana |
11. Margins of the lowest lemma in each spikelet conspicuously hairy, at least distally, the hairs 0.5-3 mm long. | → 12 |
12. Plants annual; third florets, if present, shorter than the subtending rachilla segment | C. virgata |
12. Plants perennial; third florets as long as or longer than the subtending rachilla segment. | → 13 |
13. Lowest lemmas 2.7-4.2 mm long | C. canterae |
13. Lowest lemmas 1.5-2.8 mm long. | → 14 |
14. Panicles with 2-7 branches; branches 3.5-8 cm long; awns of the first sterile florets 0.9-1.4 mm long | C. ciliata |
14. Panicles with (4)8-30 branches; branches (5)8-20 cm long; awns of the first sterile florets 0.8-4 mm long. | → 15 |
15. First sterile florets 1-1.6 mm long | C. elata |
15. First sterile florets 2.2-3.2 mm long | C. gayana |
6. Spikelets with 2 florets, 1 bisexual and 1 sterile or staminate. | → 16 |
16. Lemmas of the sterile or staminate florets bilobed for at least A of their length; lateral lobes sometimes awned. | → 17 |
17. Spikelets pectinate, diverging from the branch axes, crowded, averaging 10-14 per cm; plants annual | C. pectinata |
17. Spikelets appressed to the branch axes, not crowded, averaging 3-7 per cm; plants perennial | C. divaricata |
16. Lemmas of the sterile or staminate florets not bilobed or lobed less than 1/4 of their length; lateral lobes, if present, not awned. | → 18 |
18. Lowest (bisexual) lemmas unawned, mucronate, or shortly awned, the awns less than 1.5 mm long. | → 19 |
19. Plants annuals or short-lived perennials, sometimes shortly stoloniferous | C. pilosa |
19. Plants perennial, sometimes stoloniferous. | → 20 |
20. Lowest (bisexual) lemmas unawned, sometimes mucronate, the mucros to 1 mm long. | → 21 |
21. Sterile or staminate florets inflated, 1-1.5 mm wide and about equally long | C. cucullata |
21. Sterile or staminate florets 0.3-0.9 mm wide, usually at least twice as long | C. submutica |
20. Lowest (bisexual) lemmas always awned, the awns 1-11 mm long. | → 22 |
22. Panicles with 2-9 branches; branches 5-11 cm long | C. ventricosa |
22. Panicles with 4-28 branches (usually more than 8); branches 2-20 cm long. | → 23 |
23. Panicle branches 10-20, 2-5 cm long; spikelets with only 1 sterile floret | C. cucullata |
23. Panicle branches 4-28 (usually more than 8), 5-20 cm long, spikelets usually with 2 sterile florets, the lowest often enclosing and concealing the second | C. elata |
18. Lowest (bisexual) lemmas always awned, the awns 1.5-16 mm long. | → 24 |
24. Lowest lemmas with a conspicuous glabrous or pubescent groove on each side; plants annual or short-lived perennials | C. pilosa |
24. Lowest lemmas not conspicuously grooved on the sides; plants perennial or annual. | → 25 |
25. Margins of the lowest (bisexual) lemmas conspicuously hairy along most of their length, the hairs strongly divergent, at least some longer than 1 mm. | → 26 |
26. Plants rarely stoloniferous; second (first sterile) florets 1-1.6 mm long | C. elata |
26. Plants usually stoloniferous; second (first sterile) florets 2.2-3.2 mm long | C. gayana |
25. Margins of the lowest (bisexual) lemmas glabrous, scabrous, or appressed pubescent, sometimes with a few scattered longer hairs, or with strongly divergent hairs distally but not basally. | → 27 |
27. Panicle branches borne in 2 or more, clearly distinct whorls. | → 28 |
28. Second (first sterile) florets 0.4-0.7 mm long | C. radiata |
28. Second (first sterile) florets 0.9-2.5 mm long. | → 29 |
29. Panicle branches spikelet-bearing to the base; panicles with 10-16 branches, these usually in several, well separated whorls below a solitary, vertical branch | C. verticillata |
29. Panicle branches naked on the basal 2-5 cm; panicles with 8-10 branches, these usually digitate, sometimes a second whorl present below the terminal whorl | C. texensis |
27. Panicle branches usually digitate, in a single terminal cluster, sometimes with a poorly-developed second whorl just below the terminal cluster. | → 30 |
30. Margins of the lowest (bisexual) lemmas with conspicuously longer hairs distally than basally, the distal hairs usually more than 1.5 mm long. | → 31 |
31. Plants annual; third floret, if present, shorter than its subtending rachilla segment | C. virgata |
31. Plants perennial; third floret, if present, longer than its subtending rachilla segment | C. gayana |
30. Margins of the lowest (bisexual) lemmas glabrous or with appressed hairs less than 1 mm long, occasionally with a few scattered longer hairs. | → 31 |
32. Panicle branches without spikelets on the basal 2-5 cm | C. texensis |
32. Panicle branches spikelet-bearing to the base or naked for less than 2 cm. | → 33 |
33. Second florets (first sterile florets) 0.1-0.5 mm wide. | → 34 |
34. Plants annual, sometimes rooting at the lower nodes, not stoloniferous; second florets 0.4-0.7 mm long | C. radiata |
34. Plants perennial, not rooting at the lower nodes but sometimes stoloniferous; second florets 0.7-2.6 mm long. | → 35 |
35. Culms 10-40 cm; lowest lemmas 1.9-2.7 mm long with awns 1.9-5.2 mm long; second florets 0.9-1.7 mm long | C. andropogonoides |
35. Culms to 100 cm; lowest lemmas 2-5.4 mm long, with awns 1-11 mm long; second florets 1-2.6 mm long | C. ventricosa |
33. Second florets (first sterile florets) 0.5-1 mm wide. | → 36 |
36. Lemmas of the second florets inconspicuously bilobed; spikelets with (1)2-4 staminate or sterile florets | C. gayana |
36. Lemmas of the second florets usually not bilobed; spikelets with 1(2) staminate or sterile florets. | → 37 |
37. Panicle branches 5-23 cm long; margins of the lowest lemmas appressed pubescent, occasionally sparsely so; second florets awned, the awns 3.1-12.5 mm long; blades without basal hairs | C. truncata |
37. Panicle branches 5-11 cm long; margins of the lowest lemmas usually glabrous or scabrous, occasionally sparsely pubescent; second florets awned, the awns 0.5-7.5 mm long; blades with basal hairs up to 3 mm long | C. ventricosa |