Plains Bristlegrass
Large-spike Bristlegrass
Setaria macrostachya
Setaria vulpiseta
Photographed in Rackensack Canyon, Maricopa Co., Arizona. Aug 3, 2008.
PERENNIAL: Robust perennial grass reaching close to
1½ meters in height with good soil and moisture. Warm
season growth and flowering.
LEAVES: Leaves are about a cm wide and can range from 8 to
25 cm long.
RANGE: Fairly common in upland Sonoran Desert in Arizona ranging
eastward through Texas and the Great Plains. An important range grass.
FRUIT: There is a prominent, slightly twisted bristle below each spikelet giving
the whole spike a bristly appearance. There are several closely related species
distinguished by finer characteristics of the spikes, lemmas and glumes.
FLOWERS: The spikelets are short and presented in a dense spike
10 cm or so long. Flowering begins after start of summer rains.
UNARMED
Setaria macrostachya and S. vulpiseta have been treated as
distinct species by most authors since they were first described more than 180
years ago. In three recent publications, however, S. macrostachya was listed as
a synonym of S. vulpiseta. The present study, which included the examination of
some 350 herbarium specimens, has convinced us that these two species are as
distinct as many others in the genus, and should continue to be recognized as
separate taxa. Toolin & Reeder
(2000) Systematic Botany, Vol. 25, No. 1.