Culms 1.3-2.5 m tall, 2-4 mm wide, stiffly erect, not or only sparingly
branched; nodes hirsute, hairs 2-6 mm, stiff, spreading, tan; internodes
glaucous below the nodes. Leaves cauline; ligules 1-3 mm; blades
20-30 cm long, 4-10 mm wide, glabrous or sparsely pilose near the base. Panicles
14-25 cm long on the larger shoots, 3-6 cm wide when pressed, oblong, dense; rachises
10-20 cm, with numerous branches, rachises and branches kinked and wavy at the
base from being compressed in the sheath; branches 2-8 cm, much shorter
than the rachises, erect to appressed, with multiple rames; rame internodes
villous on the margins, with 5-8 mm distal hairs. Sessile spikelets 4.5-6
mm, ovate; lower glumes shortly pilose, with or without a dorsal pit; awns
18-22 mm; anthers about 1 mm, often remaining in the floret, light brown.
Pedicellate spikelets 3.8-4.4 mm. 2n = 120.
Bothriochloa alta grows along roads, drainage ways, and gravelly slopes
in the desert grasslands of the southwestern United States, at 600-1200 m, and
extends south to Bolivia and Argentina. It is not a common species in the Flora
region. It often grows with and is mistaken for B.
barbinodis, but differs from that species in having longer culms, panicles,
and nodal hairs, and 2n = 120. Plants in the southwestern United States
have larger spikelets and more hairy panicles than those of central Mexico, where
the species was originally described.