Panicum virgatum
Panicum bulbosum
panic raide, switch grass, switch panicgrass
bulb 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.
50-200 cm tall, 2-3(5) mm thick, with cormlike bases, slightly compressed, erect or geniculate at the lower nodes;
nodes glabrous or pilose;
internodes slightly compressed, glabrous.
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.
longer or shorter than the internodes, keeled, glabrous or pilose, hairs papillose-based near the throat;
ligules 0.5-2 mm, membranous, dissected ciliate;
blades (6)20-65 cm long, 2-15 mm wide, flat, adaxial surfaces glabrous or densely pubescent, particularly basally, occasionally pubescent on both surfaces, hairs papillose-based, bases subcordate to rounded.
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.
9-50 cm long, 1.5-12 cm wide, open;
branches opposite and alternate, straight or flexible, strongly ascending to reflexed;
pedicels 0.5-5 mm, scabridulous, divergent.
2.5-8 mm long, 1.2-2.5 mm wide, narrowly lanceoloid, turgid to slightly laterally compressed, glabrous, acuminate.
2.8-4.2(5.4) mm long, 1-2 mm wide, ellipsoid or lanceoloid, often purplish, glabrous, acute or obtuse.
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 1.2-3.5 mm, 1/2 - 4/5 as long as the spikelets, 3-5-veined;
upper glumes often longer than the lower lemmas, glabrous, 5-7-veined;
lower florets sterile or staminate;
lower lemmas glabrous;
lower paleas 3-4 mm, sometimes longer than the lower lemmas;
upper florets 3-4 mm long, 1-1.5 mm wide, equaling or surpassing the lower lemmas, dull, pale, finely transversely rugose, lemma apices puberulent.
= 18, 21, 25, 30, 32, 35, 36, 54-60, 67-72, 74, 77, 90, 108.
= 36, 54, 70, 72.
Panicum virgatum
Panicum bulbosum
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 bulbosum grows on gravelly river banks and moist mountain slopes, often in ponderosa pine woodlands, from southern Nevada and Arizona to western Texas and central Mexico. It is an important forage grass and is sometimes cut for hay. Flowering is from July to mid-October. Small plants have been called P. bulbosum var. sciaphilum (Rupr. ex E. Fourn.) Hitchc. & Chase or P. bulbosum var. minor Vasey, but size and other characters integrade completely.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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