Bothriochloa alta
Bothriochloa exaristata
tall beardgrass, tall bluestem
awnless beardgrass, awnless bluestem
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.
40-150 cm, erect;
nodes glabrous, uppermost node often concealed within the sheaths.
cauline;
ligules 1-3 mm;
blades 20-30 cm long, 4-10 mm wide, glabrous or sparsely pilose near the base.
cauline, mostly glabrous;
sheaths with a white, powdery bloom;
ligules 1-2.2 mm;
blades 10-20 cm long, 3-6(8) mm wide, flat to folded.
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.
4.5-15 cm, lanceolate;
rachises with numerous branches;
branches shorter than the rachises, erect-appressed, lacking axillary pulvini;
rame internodes with a central groove about as wide as the margins, margins densely villous, hairs 4-6 mm, obscuring the spikelets.
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.
spikelets 2.5-4 mm long, 0.6-0.8 mm wide, narrowly ovate;
lower glumes glabrous or sparsely short-pilose, lacking a dorsal pit;
awns absent or to 6 mm;
anthers 0.5-1.5 mm.
spikelets 3.8-4.4 mm.
spikelets shorter than the sessile spikelets, sterile.
= 120.
= 60.
Bothriochloa alta
Bothriochloa exaristata
Bothriochloa alta grows along roads, drainage ways, and gravelly slopes in the desert grasslands of the south-western 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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Bothriochloa exaristata grows in heavy soils of fields and roadsides of the Gulf coastal prairie, at 2-150 m, as well as in coastal areas of southern Brazil and adjacent Argentina, and inland along the Rio Pilcomayo to Paraguay. It has been reported from Los Angeles County, California. When growing in dense grassland thickets, B. exaristata has rather spindly basal growth, but branches abundantly from the middle and upper nodes.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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