26.12   BOTHRIOCHLOA Kuntze
Kelly W. Allred

Plants perennial; cespitose or stoloniferous. Culms 30-250 cm, with pithy internodes. Leaves basal or cauline, not aromatic; sheaths open; auricles absent; ligules membranous, sometimes also ciliate; blades usually flat, convolute in the bud. Inflorescences 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. 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. Pedicels similar to the internodes. Pedicellate spikelets reduced or well-developed, sterile or staminate, unawned. Caryopses lanceolate to oblong, somewhat flattened; hila punctate, basal; embryos about 1/2 as long as the caryopses. x = 10. Name from the Greek bothros, trench or pit, and chloë, grass, alluding either to the groove in the pedicels or to the pit in the lower glumes of some species.

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.


SELECTED REFERENCES Allred, K.W.1983. Systematics of the Bothriochloa saccharoides complex (Poaceae: Andropogoneae). Syst. Bot. 8:168-184; de Wet, J.M.J. 1968. Biosystematics of the Bothriochloa barbinodis complex (Gramineae). Amer. J. Bot. 55:1246-1250; de Wet, J.M.J. and J.R. Harlan. 1970. Bothriochloa intermedia-a taxonomic dilemma. Taxon 19:339-340; Vega, A.S. 2000. Revisión taxonómica de las especies americanas del género Bothriochloa (Poaceae: Panicoideae: Andropogoneae). Darwiniana 38:127-186.

1
Pedicellate spikelets about as long as the sessile spikelets (2)
Pedicellate spikelets much shorter than the sessile spikelets (5)
2
Sessile spikelets 5.5-7 mm long ..... 1. B. wrightii
Sessile spikelets 3-4.5 mm long (3)
3
Rachises longer than the branches ..... 10. B. bladhii
Rachises shorter than the branches (4)
4
Lower glumes of the sessile spikelets with a dorsal pit ..... 12. B. pertusa
Lower glumes of the sessile spikelets without a dorsal pit ..... 11. B. ischaemum
5
Sessile spikelets 2.5-4.5 mm long; awns absent or less than 17 mm long (6)
Sessile spikelets 4.5-8.5 mm long; awns 18-35 mm long(9)
6
Sessile spikelets unawned or with awns less than 6 mm long ..... 4. B. exaristata
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 ..... 10. B. bladhii
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 ..... 3. B. longipaniculata
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 ..... 2. B. laguroides
9
Rachises 5-20 cm long, with numerous branches (10)
Rachises usually less than 5 cm long, with 2-9 branches (11)
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 ..... 5. B. alta
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 ..... 6. B. barbinodis
11
Cauline nodes densely pubescent, the hairs 3-7 mm long, white, spreading ..... 7. B. springfieldii
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 ..... 8. B. hybrida
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 ..... 9. B. edwardsiana


1.   Bothriochloa wrightii (Hack.) Henrard
Wright's Bluestem

Culms to 70 cm, erect, sparingly branched; nodes glabrous or hirsute, hairs about 1 mm. Leaves cauline, glaucous; ligules 1-2 mm; blades 15-25 cm long, 3-7 mm wide, glabrous. Panicles 5-6 cm, oblong to fan-shaped; rachises 1-3 cm, with 4-5 branches; branches 4-6 cm, lacking axillary pulvini, with 1 rame; rame internodes with stiff, 1-3 mm marginal hairs. Sessile spikelets 5.5-7 mm, lanceolate-elliptic; lower glumes glabrous, usually without a dorsal pit; awns 10-15 mm, twisted, once-geniculate; anthers about 3 mm. Pedicellate spikelets staminate, subequal to the sessile spikelets. 2n = 120.

Bothriochloa wrightii grows in rocky grasslands and shrubby slopes of the pine-oak woodlands of southern Arizona, New Mexico, Texas, and northern Mexico, at 1200-1800 m. It was last collected in the United States in 1930. It differs from B. barbinodis in its glaucous foliage, short, fan-shaped panicles, and large, pedicellate spikelets.


2.   Bothriochloa laguroides (DC.) Herter
Silver Bluestem

Culms 35-115(130) cm tall, usually less than 2 mm thick, erect or geniculate at the base, branched at maturity; nodes shortly hirsute, pilose with erect hairs, or glabrous. Leaves usually basal (sometimes cauline on robust plants), usually glaucous; ligules 1-3 mm; blades 5-25 cm long, 2-7 mm wide, flat to folded, mostly glabrous. Panicles 4-12(14) cm, narrowly oblong or lanceolate, silvery-white or light tan; rachises 4-8 cm, with more than 10 branches; branches 1-5.5 cm, erect-appressed, rarely with axillary pulvini, lower branches shorter than the rachises, usually with more than 1 rame; rame internodes with a groove wider than the margins, margins copiously hairy, hairs 3-9 mm, at least somewhat obscuring the spikelets. Sessile spikelets 2.5-4.5 mm, ovate, somewhat glaucous, apices blunt; lower glumes glabrous or hirtellous, rarely with a dorsal pit; awns 8-16 mm; anthers 0.6-1.4 mm. Pedicellate spikelets 1.5-2.5(3.5) mm, shorter than the sessile spikelets, sterile. 2n = 60.

Bothriochloa laguroides grows in well-drained soils of grasslands, prairies, roadsides, river bottoms, and woodlands, often on limestone, usually at 20-2100 m. Plants from the United States and northern Mexico belong to B. laguroides subsp. torreyana, which differs from B. laguroides subsp. laguroides in its glabrous, or almost glabrous, nodes, long internode hairs, and pilose throat region. Occasional plants are found with spreading branches and axillary pulvini; they do not merit formal recognition. Bothriochloa laguroides subsp. torreyana is used in landscaping. It does well on rocky slopes and sandy banks.

Bothriochloa laguroides has been confused with B. saccharoides (Sw.) Rydb., a more southern species that differs from B. laguroides in having pilose leaves, a narrow central groove in the internodes and pedicels, and panicle branches with axillary pulvini.


3.   Bothriochloa longipaniculata (Gould) Allred & Gould
Longspike Silver Bluestem

Culms 60-150(200) cm tall, 2-4 mm thick, robust; nodes glabrous or shortly hirsute. Leaves cauline, evenly distributed, glabrous, dark green; ligules 2.5-3 mm; blades 12-20 cm long, (3)4-7 mm wide, flat to folded. Panicles 9-20 cm, narrowly lanceolate, silvery-white or light tan; rachises 7-15 cm, with numerous branches; branches 3-5 cm, shorter than the rachises, erect, without axillary pulvini, with multiple rames; rame internodes with a membranous groove wider than the margins, margins copiously hairy, hairs 3-8 mm, at least somewhat obscuring the spikelets. Sessile spikelets (3)3.5-4.5 mm, narrowly ovate to lanceolate, shiny green, apices acute; lower glumes hirtellous on the lower 1/2, hairs shorter than 0.8 mm, lacking a dorsal pit; awns 9-14 mm; anthers 1-2 mm. Pedicellate spikelets 1.8-2.8 mm, sterile. 2n = 120.

Bothriochloa longipaniculata grows at 2-200 m, along roadsides and in fields, open woodlands, disturbed ground, and swales of the Gulf coastal prairie, often in heavy clay soil. Its range extends from southern Texas and Louisiana to northeastern Mexico and possibly Panama.


4.   Bothriochloa exaristata (Nash) Henrard
Awnless Bluestem

Culms 40-150 cm, erect; nodes glabrous, uppermost node often concealed within the sheaths. Leaves 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. Panicles 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. Sessile 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. Pedicellate spikelets shorter than the sessile spikelets, sterile. 2n = 60.

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.


5.   Bothriochloa alta (Hitchc.) Henrard
Tall Bluestem

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.


6.   Bothriochloa barbinodis (Lag.) Herter
Cane Bluestem

Culms 60-120 cm tall, rarely more than 2 mm thick, erect, geniculate at the base, often branched at maturity, not glaucous below the nodes; nodes hirsute, hairs 3-4 mm, mostly erect to ascending, tan or off-white. Leaves cauline; ligules 1-2 mm, often erose; blades 20-30 cm long, 2-7 mm wide, not glaucous, glabrous or sparingly pilose near the throat. Panicles 5-14(20) cm on the larger shoots, oblong to somewhat fan-shaped, silvery-white; rachises 5-10 cm, straight, exserted or partially included in the sheath, with numerous branches; branches 4-9 cm, erect, with several rames; rame internodes with a membranous groove wider than the margins, margins densely pilose, longest hairs 3-7 mm, concentrated distally. Sessile spikelets 4.5-7.3 mm; lower glumes short pilose, with or without a dorsal pit; awns 20-35 mm; anthers 0.5-1 mm, often remaining within the spikelet. Pedicellate spikelets 3-4 mm, narrowly lanceolate, sterile. 2n = 180.

Bothriochloa barbinodis is a common species, at 500-1200 m, along roadsides, drainage ways, and gravelly slopes in desert grasslands, from the southwestern United States through Mexico and Central America to Bolivia and Argentina, and has been found in the Hawaiian Islands. Plants with a pit on the back of their lower glumes occur sporadically; they do not differ in any other respect from those without pits. The species is sometimes used as an ornamental. It is tolerant of coastal conditions and will grow as far north as Vancouver, British Columbia.

Bothriochloa barbinodis has been confused with three other species in the Flora region. It differs from B. wrightii in not having glaucous foliage, and in having oblong to merely somewhat fan-shaped panicles with pedicellate spikelets that are definitely shorter than the sessile spikelets; from B. alta in having shorter culms, panicles, and nodal hairs; and from B. springfieldii in having taller culms, wider leaves, shorter nodal hairs, and more, less hairy panicles branches.


7.   Bothriochloa springfieldii (Gould) Parodi
Springfield Bluestem

Culms 30-80 cm, erect, unbranched; nodes prominently bearded, hairs 3-7 mm, spreading, silvery-white. Leaves mostly basal; ligules 1-2.5 mm; blades 5-30 cm long, 2-3(5) mm wide, flat to folded, glabrous or sparsely hispid adaxially, pilose near the throat. Panicles 4-9 cm, oblong to fan-shaped; rachises 1-5 cm, with 2-9 branches; branches 4-8 cm, longer than the rachises, with 1(2) rames; rame internodes with a membranous groove wider than the margins, margins densely white-villous, hairs 5-10 mm, obscuring the sessile spikelets. Sessile spikelets 5.5-8.5 mm, lanceolate; lower glumes densely short-pilose on the lower 1/2, sometimes with a dorsal pit; awns 18-26 mm; anthers 1-1.5 mm. Pedicellate spikelets 3.5-5.5 mm, sterile. 2n = 120.

Bothriochloa springfieldii grows in rocky uplands, ravines, plains, sandy areas, and roadsides, from southern Utah to western Texas and Mexico at 900-2500 m and, as a disjunct, in northwest Louisiana. It differs from B. barbinodis in its less robust habit, narrower blades, longer nodal hairs, and fewer, more hairy panicle branches, and from B. edwardsiana in its pubescent nodes and wider, non-ciliate leaf blades.


8.   Bothriochloa hybrida (Gould) Gould
Hybrid Bluestem

Culms 30-80 cm, stiffly erect, moderately branched above the base; nodes glabrous or puberulent. Leaves primarily cauline; sheaths glabrous, green, sometimes glaucous; ligules 1-2 mm; blades 5-25 cm long, 2-5 mm wide, flat to folded, usually ciliate, with long hairs near the base and some hairs on the adaxial surface. Panicles 5-12 cm, lanceolate; rachises usually shorter than 5 cm; branches 3-8, without axillary pulvini, lower branches longer than the rachises; at least the lower branches rebranched and with multiple rames; rame internodes with 5-7 mm marginal hairs. Sessile spikelets 4.5-6.5 mm, narrowly ovate; lower glumes 4.5-5.7(6.5) mm, sparsely hairy near the base, with a dorsal pit above the middle; awns 18-25 mm; anthers 0.5-1 mm. Pedicellate spikelets 2.2-3.6 mm, sterile. 2n = 120.

Bothriochloa hybrida grows in open grasslands, rangeland pastures, disturbed ground, and roadsides, often on calcareous soil, usually at 50-500 m. Its range extends from southern Texas and Louisiana to central Mexico. It resembles B. edwardsiana in some respects, but the latter species has a less robust habit, more predominantly basal foliage, and narrower leaf blades.


9.   Bothriochloa edwardsiana (Gould) Parodi
Merrill's Bluestem

Culms 35-65 cm, slender, stiffly erect, rarely geniculate; lower nodes shortly hairy, hairs shorter than 3 mm, usually off-white and ascending; upper nodes glabrous or glabrate. Leaves mostly basal, glaucous; ligules 1-1.5 mm; blades 10-25 cm long, 1-2(3.5) mm wide, flat to rolled, with 3-7 mm hairs below the middle. Panicles 6-12 cm, loose, fan-shaped; rachises shorter than 5 cm, with 3-6 branches; branches longer than the rachises, not rebranched, with 1 rame; rame internodes with 3-5 mm marginal hairs. Sessile spikelets 5-8 mm, lanceolate; lower glumes 5.5-7 mm, glabrous, shiny, with a deep dorsal pit, tapering to a narrow, slightly bifid apex; awns 20-28 mm; anthers 0.5-1 mm. Pedicellate spikelets 2.5-3.5 mm, sterile. 2n = 60.

Bothriochloa edwardsiana grows in the rocky plains and prairies of the Edwards Plateau of Texas, on calcareous soil, at 300-600 m. It also grows in northern Mexico and Uruguay. It resembles B. hybrida in some respects, but that species has a more robust habit, predominantly cauline foliage, and wider leaf blades.


10.   Bothriochloa bladhii (Retz.) S.T. Blake
Australian Bluestem

Culms 40-90(150) cm, usually erect; nodes glabrous or short hispid, with mostly appressed, less than 2 mm hairs. Leaves cauline; ligules 0.5-1.5 mm; blades (10)20-35(40) cm long, 1-4.5(5.5) mm wide, mostly glabrous. Panicles 5-15(24) cm, elliptic to lanceolate, reddish at maturity; rachises 6-12(20) cm, with numerous branches; branches 3-7 cm, shorter than the rachises, erect to spreading during anthesis, with axillary pulvini, lower branches with multiple rames; rame internodes with darkened grooves, with sparse, about 1 mm marginal hairs. Sessile spikelets 3.5-4 mm, oblong-ovate; lower glumes glabrous or scabrous, with or without a dorsal pit; awns 10-17 mm, twisted, geniculate; anthers 1-2 mm. Pedicellate spikelets about the same size and shape as the sessile spikelets, or about 1/2 their size, staminate or sterile. 2n = 40, 60, 80.

Bothriochloa bladhii grows along roadsides and in rangeland pastures, waste ground, and open disturbed areas, at 150-1800 m. It is native to subtropical Asia and Africa and was introduced to the Flora region as a forage grass. It is now established in the southern and central United States. A similar species, B. decipiens (Hack.) C.E. Hubb., has been grown at some experiment stations in the United States. It is not known to be established in North America. Bothriochloa decipiens differs from B. bladhii in having longer (4.7-5.3 mm) sessile spikelets and a single anther.

The Eastern Hemisphere species of Bothriochloa are thought to be closely related to Capillipedium and Dichanthium, largely because B. bladhii hybridizes with those genera as well as with B. ischaemum.


11.   Bothriochloa ischaemum (L.) Keng

Plants usually cespitose, occasionally stoloniferous or almost rhizomatous under close grazing or cutting. Culms 30-80(95) cm, stiffly erect; nodes glabrous or short hirsute. Leaves tending to be basal; ligules 0.5-1.5 mm; blades 5-25 cm long, 2-4.5 mm wide, flat to folded, glabrous or with long, scattered hairs at the base of the blade. Panicles 5-10 cm, fan-shaped, silvery reddish-purple; rachises 0.5-2 cm, with (1)2-8 branches; branches 3-9 cm, longer than the rachises, erect to somewhat spreading from the axillary pulvini, usually with only 1 rame; rame internodes with a central groove narrower than the margins, margins ciliate, with 1-3 mm hairs. Sessile spikelets 3-4.5 mm, narrowly ovate; lower glumes hirsute below, with about 1 mm hairs, lacking a dorsal pit; awns 9-17 mm, twisted, geniculate; anthers 1-2 mm. Pedicellate spikelets about as long as the sessile spikelets, but usually narrower, sterile or staminate. 2n = 40, 50, 60.

Bothriochloa ischaemum grows along roadsides and in waste ground and rangeland pastures, at 50-1200 m. It is native to southern Europe and Asia. It was introduced to the United States for erosion control along right of ways and for livestock forage in the southwest. It is now established in the region and has spread along roadsides into other central and southern states. There are two variants that are sometimes recognized as varieties, plants with glabrous nodes being called B. ischaemum (L.) Keng var. ischaemum, and plants with pubescent nodes being called B. ischaemum var. songarica (Rupr. ex Fisch. & C.A. Mey.) Celarier & J.R. Harlan.


12.   Bothriochloa pertusa (L.) A. Camus
Pitted Bluestem

Plants cespitose or stoloniferous. Culms to 100 cm, often decumbent or stoloniferous, freely branching; nodes bearded. Leaves mostly basal, green, sometimes glaucous; sheaths glabrous, keeled; ligules 0.7-1.5 mm; blades 3-15 cm long, 3-4 mm wide, flat, margins and ligule regions hairy. Panicles 3-5 cm, fan-shaped, often purplish; rachises 0.2-2 cm, with 3-8 branches; branches 3-4.5 cm, longer than the rachises, usually with 1 rame; rame internodes with villous margins, with 1-3 mm hairs. Sessile spikelets 3-4 mm, lanceolate; callus hairs about 1 mm; lower glumes sparsely hirtellous, with a prominent dorsal pit near the middle; awns 10-17 mm; anthers 1-1.8 mm, yellow. Pedicellate spikelets the same size as the sessile spikelets, sterile, pitted or not, occasionally with 2 pits. 2n = 40, 60.

Bothriochloa pertusa is native to the Eastern Hemisphere, and was introduced to the southern United States as a warm-season pasture grass. It now grows in disturbed, moist, grassy places and pastures in the region, at elevations of 2-200 m. It has not persisted at all locations shown on the map.