Panicum rigidulum

Plants perennial; cespitose, not rhizomatous, occasionally purple-tinged throughout, mostly glabrous throughout (except as noted). Culms 35-150 cm, stout, compressed. Sheaths more or less strongly compressed or keeled, sides usually glabrous or sparsely pubescent distally; ligules 0.3-3 mm, membranous, erose or ciliate, cilia often themselves fimbriate; blades 8-50 cm long, 2-12 mm wide, flat or folded, both surfaces usually glabrous or scabridulous, or the adaxial surfaces sparsely pilose basally. Panicles terminal and axillary, 9-40 cm, 1/3 – 3/4 as wide as long, usually dense; ultimate branchlets usually appressed, 1-sided, scabridulous; pedicels 0.5-1.5 mm, usually appressed, sometimes with 1-several slender hairs at the apices. Spikelets usually 1.6-3.8 mm, usually subsessile, lanceolate, green, purple-tinged, or purple, glabrous. Lower glumes 2/5 – 3/4 as long as the spikelets, 3-veined, midveins keeled; upper glumes and lower lemmas subequal or the glumes slightly longer, often spreading slightly apart at the apices, midveins keeled, usually scabridulous apically; lower florets sterile; lower paleas to 2/3 as long as the lower lemmas; upper florets 1.4-2 mm long, 0.6-0.8 mm wide, 2/5 – 3/4 as long as the spikelets, occasionally stipitate, lustrous, with a tuft of minute, thickish hairs at the apices; upper lemmas thick, stiff, clasping the upper paleas throughout their length. 2n =18.

Distribution

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• Legacy Map

Conn., N.J., N.Y., W.Va., Del., D.C., Wis., B.C., N.S., Ont., Mass., Maine, N.H., R.I., Vt., Fla., Ala., Kans., Ky., La., Mo., Okla., Pa., Tenn., Tex., Va., Puerto Rico, N.C., S.C., Md., Calif., Miss., Ark., Ill., Ga., Ind., Mich., Ohio, Oreg.

Discussion

Panicum rigidulum grows in swamps, wet woodlands, flood-plain forests, wet pine savannahs, marshy shores of rivers, ponds, and lakes, drainage ditches, and other similar wet to moist places; it is rarely found in dry sites. Its range extends from southern Canada to Mexico, Guatemala, and the Antilles.

Selected References

None.

Lower Taxa

Panicum rigidulum subsp. abscissum, Panicum rigidulum subsp. combsii, Panicum rigidulum subsp. elongatum, Panicum rigidulum subsp. pubescens, Panicum rigidulum subsp. rigidulum

Key

1	Sheaths truncate or broadly auriculate; blade bases much narrower than the subtending sheaths	Panicum rigidulum subsp. abscissum
1	Sheaths not truncate or broadly auriculate; blade bases about as wide as the subtending sheaths.	> 2
2	Blades usually 5-12 mm wide, flat, mostly glabrous or scabridulous; ligules membranous, 0.3-1 mm long.	> 3
3	Spikelets 1.6-2.5 mm long, usually over 0.6 mm wide, green or purplish-tinged	Panicum rigidulum subsp. rigidulum
3	Spikelets 2.4-3 mm long, usually less than 0.6 mm wide, conspicuouly stipitate, usually purple	Panicum rigidulum subsp. elongatum
2	Blades usually 2-7 mm wide, often folded or involute, usually pilose adaxially, at least near the base; ligules membranous, the cilia usually fimbriate, 0.5-3 mm long.	> 4
4	Spikelets 2-2.7 mm long, green or purplish-stained, often obliquely set on the pedicels	Panicum rigidulum subsp. pubescens
4	Spikelets 2.6-3.8 mm long, usually purple, slender, erect on the pedicels	Panicum rigidulum subsp. combsii