Panicum rigidulum
Panicum coloratum
redtop panic grass, redtop panicum, smooth witchgrass
kleingrass
35-150 cm, stout, compressed.
50-140 cm tall, 1.5-2.5 mm thick, usually erect, rarely decumbent, firm;
nodes glabrous or puberulent;
internodes glabrous.
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.
shorter than the internodes, glabrous or hispid, hairs papillose-based, rounded basally;
ligules 0.5-2 mm;
blades 10-30 cm long, 2-8 mm wide, flat, glabrous or sparsely hirsute on 1 or both surfaces.
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.
4-25(40) cm long, 3-14 cm wide, exerted, lax;
primary branches 3-14 cm, opposite and alternate, ascending, glabrous, branching in the distal M;
pedicels 1-4 mm, appressed or spreading.
usually 1.6-3.8 mm, usually subsessile, lanceolate, green, purple-tinged, or purple, glabrous.
2.5-3.5 mm long, 1-1.2 mm wide, narrowly ovoid to ellipsoid, glabrous, acute.
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.
1-1.5 mm, about 1/3 as long as the spikelets, glabrous, 1-3-veined, acute;
upper glumes slightly exceeding the lower lemmas, glabrous, acute, scarcely separated from the lower lemmas;
lower florets staminate;
lower lemmas similar to the upper glumes;
lower paleas 2-3 mm, oblong;
upper florets 2-2.5 mm long, 0.8-1 mm wide, ellipsoid, widest below the middle, glabrous, smooth, shiny, apices lightly beaked.
=18.
= 18, 36, 41, 42, 43, 45, 54, 63 (United States material apparently usually tetraploid, with 2n = 36).
Panicum rigidulum
Panicum coloratum
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Panicum coloratum is an African species that has been widely introduced into tropical and subtropical regions around the world. It is now established in the Flora region, growing in open, usually wet ground; it is also occasionally cultivated as a forage grass.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Sheaths truncate or broadly auriculate; blade bases much narrower than the subtending sheaths | 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 | subsp. rigidulum |
3. Spikelets 2.4-3 mm long, usually less than 0.6 mm wide, conspicuouly stipitate, usually purple | 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 | subsp. pubescens |
4. Spikelets 2.6-3.8 mm long, usually purple, slender, erect on the pedicels | subsp. combsii |
- Local floras:
BC, 
OR - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
