Bothriochloa alta
Bothriochloa
tall beardgrass, tall bluestem
beardgrass
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.
30-250 cm, with pithy internodes.
cauline;
ligules 1-3 mm;
blades 20-30 cm long, 4-10 mm wide, glabrous or sparsely pilose near the base.
basal or cauline, not aromatic;
sheaths open;
auricles absent;
ligules membranous, sometimes also ciliate;
blades usually flat, convolute in the bud.
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.
terminal, panicles of subdigitate to racemosely arranged branches, each branch with (1)2-many rames, branches not subtended by modified leaves;
rames with spikelets in heterogamous sessile-pedicellate pairs, internodes with a translucent, longitudinal groove, often villous on the margins;
disarticulation in the rames, beneath the sessile spikelets.
dorsally compressed;
sessile spikelets with 2 florets;
lower glumes rounded, several-veined, sometimes with a dorsal pit, margins clasping the upper glume;
upper glumes somewhat keeled, 3-veined;
lower florets hyaline scales, unawned;
upper florets bisexual;
upper lemmas with a midvein that usually extends into a twisted, geniculate awn, occasionally unawned;
anthers 3.
lanceolate to oblong, somewhat flattened;
hila punctate, basal;
embryos about Yi as long as the caryopses.
similar to the internodes.
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 3.8-4.4 mm.
spikelets reduced or well-developed, sterile or staminate, unawned.
= 10.
= 120.
Bothriochloa alta
Bothriochloa
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 is a genus of about 35 species that grow in tropical to warm-temperate regions. Nine are native to the Flora region; three Eastern Hemisphere species have been introduced into the southern United States for forage and range rehabilitation. Most species provide fair forage in summer and fall. Polyploidy has been an important mechanism of speciation in the genus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Pedicellate spikelets about as long as the sessile spikelets. | → 2 |
2. Sessile spikelets 5.5-7 mm long | B. wrightii |
2. Sessile spikelets 3-4.5 mm long. | → 3 |
3. Rachises longer than the branches | B. bladhii |
3. Rachises shorter than the branches. | → 4 |
4. Lower glumes of the sessile spikelets with a dorsal pit | B. pertusa |
4. Lower glumes of the sessile spikelets without a dorsal pit | B. ischaemum |
1. Pedicellate spikelets much shorter than the sessile spikelets. | → 5 |
5. Sessile spikelets 2.5-4.5 mm long; awns absent or less than 17 mm long. | → 6 |
6. Sessile spikelets unawned or with awns less than 6 mm long | B. exaristata |
6. Sessile spikelets with awns 8-17 mm long. | → 7 |
7. Panicles reddish when mature; hairs below the sessile spikelets about 1/4 as long as the spikelets, sparse, not obscuring the spikelets | B. bladhii |
7. Panicles silvery-white or light tan; hairs below the sessile spikelets at least 1/2 as long as the spikelets, copious, at least somewhat obscuring the spikelets. | → 8 |
8. Panicles 9-20 cm long; sessile spikelets narrowly ovate to lanceolate; glumes acute; leaves evenly distributed on the culms; culms 2-4 mm thick | B. longipaniculata |
8. Panicles 4-12(14) cm long; sessile spikelets ovate; glumes blunt; leaves often clustered at the base of the culms; culms usually less than 2 mm thick | B. laguroides |
5. Sessile spikelets 4.5-8.5 mm long; awns 18-35 mm long. | → 9 |
9. Rachises 5-20 cm long, with numerous branches. | → 10 |
10. Panicles of the larger shoots 14-25 cm long; culms 130-250 cm tall, 2-4 mm thick, stiffly erect, little-branched distally, glaucous below the nodes; nodes with spreading hairs, the hairs 2-6 mm long | B. alta |
10. Panicles of the larger shoots 5-14(20) cm long; culms usually 60-120 cm tall, usually less than 2 mm thick, tending to be bent at the base and often branched at maturity, not glaucous below the nodes; nodes with ascending hairs less than 3 mm long | B. barbinodis |
9. Rachises usually less than 5 cm long, with 2-9 branches. | → 11 |
11. Cauline nodes densely pubescent, the hairs 3-7 mm long, white, spreading | B. springfieldii |
11. Cauline nodes glabrous or puberulent, the hairs always less than 3 mm long, usually off-white and ascending. | → 12 |
12. Lower branches of the inflorescences rebranched; sessile spikelets 4.5-6.5 mm long; lower glumes sparsely hairy near the base; leaves primarily cauline, the blades 2-5 mm wide | B. hybrida |
12. Lower branches of the inflorescences simple, not rebranched; sessile spikelets 5-8 mm long; lower glumes glabrous; leaves primarily basal, the blades usually less than 2 mm wide | B. edwardsiana |
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