Plants annual or perennial; cespitose, occasionally rhizomatous. Culms 14-100 cm, ascending to erect; nodes pubescent to hirsute. Sheaths open; auricles absent; ligules of hairs or membranous and ciliate; blades 1-5 mm wide, flat or involute. Primary inflorescences terminal, open panicles, with few spikelets, exerted or partially included in the upper sheath, apices exceeding the upper leaf blades, axillary panicles sometimes also present; cleistogamous inflorescences also present in the upper sheaths. Spikelets laterally compressed, purplish, with 2-5 florets; sterile florets above the fertile florets; rachillas prolonged; disarticulation above the glumes and beneath the florets and, subsequently, at the cauline nodes. Glumes equal or unequal, shorter than the first lemma, 1-veined, keeled; calluses hairy; lemmas 3-veined, veins villous, apices bilobed to incised, midveins sometimes extending into an awn, awns to 11 mm; paleas bowed-out, keels hairy, distal hairs 0.5-2 mm, longer than those below; lodicules 2, truncate; anthers 3, yellow or reddish-purple; stigmas pink to purple. Caryopses dorsiventrally compressed, x = 10.
Distribution
Conn., N.J., N.Y., Del., Wis., Fla., N.H., N.Mex., Tex., La., Tenn., N.C., S.C., Pa., Va., Colo., Ont., Ala., Kans., N.Dak., Nebr., Okla., S.Dak., Ark., Ill., Ga., Ind., Iowa, Ky., Maine, Md., Mass., Ohio, Mo., Mich., R.I., Miss., Oreg.
Discussion
Triplasis is an American genus of two species that is probably related to Tridens. The disarticulating culm, which helps disperse the cleistogenes, aids in distinguishing Triplasis from other genera.
Selected References
None.
Lower Taxa
Key
| 1 | Lemmas with lobes 4.5-8 mm long, tapering to acute tips; lemma awns 5-11 mm long; culm internodes puberulent to pilose | Triplasis americana |
| 1 | Lemmas with lobes about 1 mm long, rounded; lemma awns less than 2 mm long; culm internodes glabrous | Triplasis purpurea |