Panicum virgatum
Panicum anceps
panic raide, switch grass, switch panicgrass
beak panicgrass
40-300 cm tall, 3-5 mm thick, solitary or forming dense clumps, erect or decumbent, usually simple;
nodes glabrous;
internodes hard, glabrous or glaucous, green or purplish.
30-130 cm, terete to slightly compressed.
longer than the lower internodes, shorter than those above, glabrous or pilose, especially on the throat, margins usually ciliate;
ligules 2-6 mm;
blades 10-60 cm long, 2-15 mm wide, flat, erect, ascending or spreading, glabrous or pubescent, adaxial surfaces sometimes densely pubescent, particularly basally, bases rounded to slightly narrowed, margins scabrous.
laterally compressed, glabrous or sparsely to densely pilose or villous, especially at the summit;
ligules less than 0.5 mm, membranous, erose, often brownish;
blades 10-50 cm long, 4-12 mm wide, erect, adaxial surfaces pilose at least basally, glabrous or pilose abaxially.
10-55 cm long, 4-20 cm wide, exserted, open;
primary branches thin, straight, solitary to whorled or fascicled, ascending to spreading, scabrous, usually rebranching once;
pedicels 0.5-20 mm, appressed to spreading.
10-40 cm, 1/4 - 2/3 as wide as long, well-exserted at anthesis;
branches relatively few, stiffly spreading or ascending; ultimate branchlets 1-sided;
pedicels 0.1-3 mm, scabridulous to scabrous, appressed.
2.5-8 mm long, 1.2-2.5 mm wide, narrowly lanceoloid, turgid to slightly laterally compressed, glabrous, acuminate.
2.3-3.9 mm, narrowly ellipsoid to ovoid, usually subsessile, usually pale to yellowish-green, glabrous, often falcate and gaping at the apices, rarely lanceolate, densely crowded on short, appressed branchlets, set obliquely on short pedicels.
glumes 1.8-3.2 mm, 1/2 - 4/5 as long as the spikelets, glabrous, 5-9-veined, acuminate;
upper glumes and lower lemmas extending 0.4-3 mm beyond the upper florets, 7-11-veined, strongly gaping at the apices;
lower florets staminate;
lower paleas 3-3.5 mm, ovate-hastate, lateral lobes folded over the anthers before anthesis;
upper florets 2.3-3 mm long, 0.8-1.1 mm wide, narrowly ovoid, smooth, glabrous, shiny;
upper lemmas clasping the paleas only at the base.
glumes A-A as long as the spikelets, 3-veined, keels scabrous, apices acute;
upper glumes and lower lemmas subequal, keeled, beaked, usually gaping at the apices;
lower florets sterile;
lower paleas subequal to the lower lemmas;
upper florets 1.5-2.2 mm long, about 1 mm wide, 2/5 – 3/4 as long as the spikelets, apices with a tuft of minute, thick hairs;
upper lemmas thick, stiff, clasping the upper paleas throughout their length.
= 18, 21, 25, 30, 32, 35, 36, 54-60, 67-72, 74, 77, 90, 108.
= 18, 36.
Panicum virgatum
Panicum anceps
Panicum virgatum grows in tallgrass prairies, especially mesic to wet types where it is a major component of the vegetation, and on dry slopes, sand, open oak or pine woodlands, shores, river banks, and brackish marshes. Its range extends, primarily on the eastern side of the Rocky Mountains, from southern Canada through the United States to Mexico, Cuba, Bermuda, and Costa Rica, and, possibly as an introduction, in Argentina. It has also been introduced as a forage grass to other parts of the world.
Panicum virgatum is an important and palatable forage grass, but its abundance in native grasslands decreases with grazing. Several types are planted for range and wildlife habitat improvement. Plants from eastern New Mexico, western Texas, and northern Mexico tend to have larger spikelets (6-8 mm versus 2.5-5.5 mm) and are sometimes called P. havardii Vasey Tetraploids appear to be the most common ploidy level, especially in the upper midwest and northern plains, with higher ploidy levels being more common southwards, but plants in a small area can range from diploid through duodecaploid, with dysploid derivatives. If morphological markers matched chromosome numbers and ecotypic characters, the species could be considered an aggregate of numerous microspecies. In the absence of such correlations, it must be regarded as simply a wide-ranging, highly variable taxon. Plants identified as Panicum virgatum var. cubense Griseb. and P. virgatum var. spissum Linder represent end points of geographic clines.
Panicum virgatum is not always readily separable from P. amarum, particularly P. amarum subsp. amarulum; future work may support their treatment as conspecific taxa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Panicum anceps grows in low, moist, primarily sandy areas, pine savannahs, the borders of flood-plain swamps, mesic woodlands, roadsides, and upland pine-hardwood forests. It is restricted to the United States.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Spikelets 2.7-3.9 mm long, often clearly falcate; rhizomes relatively short and stout | subsp. anceps |
1. Spikelets 2.3-2.8 mm long, not clearly falcate; rhizomes relatively long and slender | subsp. rhizomatum |
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