Plants annual or perennial; synoecious; habit various, cespitose, stoloniferous, or rhizomatous. Culms 1-80 cm. Leaves usually mostly basal; sheaths open; ligules of hairs, membranous, or membranous and ciliate. Inflorescences terminal, panicles of 1-80 solitary, spikelike branches, exceeding the upper leaves; branches 4-50(75) mm, not woody, 1-sided, usually racemose on elongate rachises, sometimes digitate or subdigitate, with 1-130+ sessile to subsessile spikelets in 2 rows, axes terminating in a spikelet or extending beyond the base of the distal spikelet. Spikelets closely imbricate, appressed to pectinate, laterally compressed or terete, with 1-2(3) florets, lowest floret in each spikelet bisexual, distal florets staminate or sterile; disarticulation at the base of the branches or above the glumes. Glumes unequal or subequal, 1 or both glumes equaled or exceeded by the distal floret, 1-veined, acute or acuminate, sometimes shortly awned; lower glumes usually shorter than the lowest floret; lemmas of lowest florets entire, bilobed, trilobed, or 4-lobed, 3-veined, veins usually extended into 3 short awns; paleas of lowest florets 2-veined, veins sometimes excurrent; distal floret(s) staminate or sterile, varying from similar to the lowest floret in shape, size, and venation to sterile and reduced to an awn column with well-developed awns or to a flabellate scale. x = 10. Named for the brothers Claudio (1774-1842) and Esteban (1776-1813) Boutelou Agraz, Spanish botanists.

Bouteloua, a genus of the Western Hemisphere with its center of diversity in Mexico, has about 40 species; all 19 species treated here are native to the Flora region. Several of its taxa are important forage grasses, and some are important constituents of the native North American grasslands. Two that are particularly important in North America are Bouteloua curtipendula and B. gracilis. These were major constituents of the shortgrass prairie that once covered the drier portions of the Great Plains. Both are excellent forage species. Irrigation has converted much of the area they once occupied to agricultural use, but large areas of Bouteloua grasslands remain.

Based on molecular data and morphological similarities in the non-pistillate characters, Columbus (1999) recommended expanding Bouteloua to include Buchloë, Opizia, and Cathestecum, plus some other small genera not known from the Flora region. The traditional treatment is adopted here, pending corroboration from a wider range of data, both molecular and morphological.

Bouteloua Lag. subg. Bouteloua

Panicle branches (1)4-80, with 1-15 spikelets, terminating beyond the distal spikelet in an entire, bifurcate, or trifurcate tip; spikelets usually appressed; disarticulation at the base of the branches.

1.   Bouteloua curtipendula (Michx.) Torr.
Sideoats Grama

Plants perennial; cespitose or not, with or without rhizomes. Culms 8-80 cm, erect or decumbent, solitary or in small to large groups. Leaves evenly distributed; sheaths mostly glabrous, sometimes with hairs distally; ligules 0.3-0.5 mm, membranous, ciliate; blades 2-30 cm long, (1.4)2.5-7 mm wide, at least some over 2.5 mm wide, flat or folded when dry, usually smooth abaxially and scabrous adaxially, occasionally pubescent, bases usually with papillose-based hairs on the margins. Panicles 13-30 cm, secund, with (12)30-80 reflexed branches; branches (5)10-30(40) mm, deciduous, with (1)2-7(15) spikelets, axes terminating 3-5 mm beyond the base of the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, all alike, with 1 bisexual and 1-2 sterile, rudimentary florets. Glumes unequal, glabrous or scabrous; lower glumes 2.5-6 mm, 1/2 or more as long as the upper glumes; upper glumes 5.5-8 mm; lowest lemmas 3-6.5 mm, glabrous or scabrous-strigose, often minutely rugose, acute or inconspicuously 3-lobed, 3-veined, veins usually extending as short mucros or awns to 6 mm; central mucros or awns not flanked by membranous lobes; lowest paleas acute, unawned; anthers 1.5-3.5 mm, yellow, orange, red, or purple; distal floret(s) 0.4-3.5 mm, sterile, variable, usually a glabrous lemma having a short membranous base, no palea, and 3 unequally-developed awns, central awns 1.5-7 mm. 2n = (20), 40, 41-103.

Bouteloua curtipendula is a common, often dominant or co-dominant species in open grasslands and wetlands of the drier portions of the central grasslands of North America. It ishighly regarded as a forage species and is also an attractive ornamental. Its range extends from the Flora region through Mexico and Central America to western South America.

As the range of chromosome numbers suggests, B. curtipendula is an apomictic species. There are three varieties. Two of the three grow in the Flora region; the third, B. curtipendula var. tenuis, is endemic to Mexico.

Bouteloua curtipendula var. caespitosa Gould & Kapadia

Plants cespitose, often with a knotty base, not or shortly rhizomatous. Culms in large or small clumps, stiffly erect. Blades usually narrow, but at least some over 2.5 mm wide. Panicles with 12-80 branches, averaging 2-7 spikelets per branch. Glumes and lemmas bronze or stramineous to green, or various shades of purple; anthers usually yellow or orange, occasionally red or purple. 2n = 58-103.

Bouteloua curtipendula var. caespitosa grows on loose, sandy or rocky, well drained limestone soils at 200-2500 m in the southwestern United States, Mexico, and South America. It frequently grows, and may hybridize, with B. warnockii.

Bouteloua curtipendula (Michx.) Torr. var. curtipendula

Plants not cespitose, with long rhizomes. Culms solitary or in small clumps. Blades 3-7 mm, flat. Panicles with 40-70 branches, averaging 3-7 spikelets per branch. Glumes and lemmas typically purple or purple-tinged; anthers red or red-orange, infrequently yellow, orange, or purple. 2n = 40, 41-66.

Bouteloua curtipendula var. curtipendula is the common variety of B. curtipendula in most of the Flora region. It grows on rich, loamy, well-drained prairie soils. Its elevational range extends from below 100 m to 2500 m.

2.   Bouteloua warnockii Gould & Kapadia
Warnock's Grama

Plants perennial; cespitose, forming clumps 4-10 cm in diameter, without rhizomes or stolons. Culms 20-35(50) cm, stiffly erect. Leaves bluish-green, more or less glaucous; sheaths mostly glabrous, hairs present distally; ligules 1-1.5 mm, of hairs; blades 5-15(25) cm long, 1-1.5(2.5) mm wide, stiffly erect or curving, involute when dry; mostly glabrous, ligular area with long and short hairs, bases usually with papillose-based hairs on the margins. Panicles 5-13(20) cm, with 9-15(30) branches; branches 4-5.5 mm, deciduous, scabrous, with 2-6 spikelets, axes terminating well beyond the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets 5-6.5 mm, with 1 bisexual and 1 sterile floret, appressed, all alike, green, often with a brownish or purplish cast. Lower glumes slightly shorter than the upper glumes, both usually exceeded by the lemmas of the lowest florets; upper glumes glabrous, sometimes scabrous; lowest lemmas glabrous, acute, 3-awned, awns less than 1 mm, central awns not flanked by 2 membranous lobes; anthers 2.2-3.7 mm, dark purple; second florets sterile, usually without paleas; second lemmas reduced to a glabrous awn column, sometimes moderately well-developed and 3-awned, awns usually not exserted, central awns to 2.5 mm. 2n = 21, 22, 23, 24, 25, 28, 38, 40.

Bouteloua warnockii grows on limestone ledges and dry slopes below limestone outcrops. Its range extends from the southwestern United States to the state of Coahuila in northern Mexico. It frequently grows, and may hybridize with, B. curtipendula var. caespitosa.

3.   Bouteloua uniflora Vasey
Nealley's Grama

Plants perennial; cespitose, without rhizomes or stolons. Culms 20-60 cm, stiffly erect, glabrous. Sheaths mostly glabrous, a few long hairs present near the ligules; ligules 0.2-0.5 mm, of hairs; blades 6-16 cm long, 1-2 mm wide, involute when dry, glabrous, bases usually with papillose-based hairs on the margins. Panicles 5-10(14) cm, with 15-70 branches; branches 5-9 mm, deciduous, scabrous, with 1 spikelet (lower branches occasionally with 2 spikelets), axes extending 3-4 mm beyond the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, with 1 bisexual and 0-1 rudimentary florets. Glumes acute to slightly cleft and minutely apiculate, midveins usually scabrous; lower glumes 2.5-4 mm; upper glumes 6.2-8 mm, mostly smooth, midveins usually scabrous; lowest lemmas 6-7.5 mm, acute or minutely cleft, glabrous, unawned, sometimes mucronate; lowest paleas unawned, glabrous; anthers 2.5-3 mm, bright yellow; second florets absent or reduced to 1 or 3 short awns, glabrous. Caryopses about 3 mm. 2n = 20.

Bouteloua uniflora grows primarily in fertile, rocky, limestone soils of Texas and adjacent Coahuila, Mexico at 300-1000 m. A disjunct collection has been reported from Zion National Park, Utah. Plants in the Flora region belong to Bouteloua uniflora Vasey var. uniflora, which differs from B. uniflora var. coahuilensis Gould & Kapadia in having taller (40-60 cm, not 20-40 cm) leafy, rather than scapose, culms, longer leaf blades (12-16 cm versus 6-12 cm), and 50-70, rather than 15-40, panicle branches.

4.   Bouteloua aristidoides (Kunth) Griseb.

Plants annual; tufted. Culms 4-60 cm, outer culms of a tuft decumbent, sometimes geniculate, branched at the lower nodes. Ligules 0.2-0.5 mm, membranous, lacerate or ciliate; blades 2-5(9) cm long, 0.7-2 mm wide, flat or folded, adaxial surfaces sometimes with papillose-based hairs, margins usually with papillose-based hairs near the ligules. Panicles 2.5-10.5 cm, with (1)4-15 branches; branches 5-45 mm, deciduous, densely pubescent (at least basally), with 2-10 spikelets per branch, axes extending 2-10 mm beyond the base of the terminal spikelets, apices entire; disarticulation at the base of the branches, the break forming a sharp tip. Spikelets appressed. Proximal spikelet on each branch with 1 floret; lower glumes 1.5-3.5 mm, glabrous, narrow to subulate; upper glumes 5.5-6.2 mm, densely pubescent, at least on the basal 1/2; lemmas 5.8-6 mm, acuminate, unawned; lowest paleas almost as long as the lemmas, bifid, glabrous; rachillas prolonged beyond the florets for about 0.5 mm. Distal spikelets with 1 bisexual and 1 rudimentary floret;glumes unequal, glabrous, minutely scabrous on the keels; narrowly acute or acuminate; lower glumes 1.5-2 mm; upper glumes 5-6 mm, glabrous or sparsely pubescent basally, often divergent; lowest lemmas 6-8 mm, veins pubescent, lateral veins excurrent as short (to 1 mm) awns, acuminate, midvein extended into a setaceous tip or a short awn; lowest paleas 5-7 mm, bifid, veins often excurrent as short awns; anthers about 2.5 mm, yellow or yellow and red; distal florets reduced to a pubescent, 3-awned, awn column, awns 2-7 mm, exserted. Caryopses 2.5-3 mm. 2n = 40.

There are two varieties, both of which grow in the Flora region.

Bouteloua aristidoides (Kunth) Griseb. var. aristidoides
Needle Grama

Panicle branches 5-16 mm to the base of the terminal spikelets and extending an additional 6-10 mm, with 2-5 spikelets.

Bouteloua aristidoides var. aristidoides grows in dry mesas, plains, and washes from near sea level to about 2000 m. It matures rapidly following summer rains, and can be abundant over large areas within its range, which extends from California to western Texas and Mexico.

Bouteloua aristidoides var. arizonica M.E. Jones
Arizona Needle Grama

Panicle branches 15-35 mm to the base of the terminal spikelets and extending an additional 1.5-5(7) mm, with 6-10 spikelets.

Bouteloua aristidoides var. arizonica grows in the same kind of habitats as var. aristidoides, but only from 500-800 m. It has a more restricted range than B. aristidoides var. aristidoides (which extends into northern Mexico), being known only from New Mexico, Arizona, and Chihuahua, Mexico. In its extreme form, var. arizonica is very different from var. aristidoides, but the two varieties do intergrade.

5.   Bouteloua eludens Griffiths
Elusive Grama

Plants perennial; without rhizomes or stolons. Culms 20-60 cm, unbranched. Leaves mostly basal; sheaths glabrous or sparsely ciliate near the throat, basal sheaths papery, becoming pale; ligules to 0.5 mm, of hairs; blades to 15 cm long, 1-1.5(3) mm wide, flat, lower leaves variously hispid or scabrous, upper leaves glabrous, with scabrous margins. Panicles 6-10 cm, with (8)12-16(20) branches; branches 5-11 mm, deciduous, pubescent, with (2)4-6 spikelets, axes extending about 5 mm beyond the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, all alike, with 1-2 bisexual florets and 1 rudimentary floret. Glumes silvery-hispid over and between the veins, at least basally, apices acute, acuminate, or shortly awned; lower glumes 5-6 mm; upper glumes 6-7 mm, sericeous over the veins and elsewhere, hairs about 0.5 mm, apices mucronate; lowest florets bisexual, pistillate, or staminate; lowest lemmas 6-7 mm, pubescent between the veins and over the midveins, midveins extending into acuminate or setaceous lobes about the same length as the lateral lobes, not flanked by membranous lobes, lateral veins extending from the lateral lobes for 0.5-2 mm; lowest paleas as long as the lemmas, pubescent, acute to acuminate, unawned; second florets usually staminate, pistillate, or bisexual (rarely rudimentary); second lemmas 8-10 mm; usually well-developed, pubescent, lateral veins extended into 0.5-4 mm awns, midveins extended into a flattened, 1-5 mm awn; second paleas as long as the second lemmas, pubescent, usually with 2 short awns; third florets, if present, pubescent, variable, resembling the second floret, a 3-awned structure with 2 membranous scales, or a prolongation of the rachilla. Caryopses about 5 mm long, about 1.5 mm wide. 2n = 20.

Bouteloua eludens grows on dry, rocky slopes and rolling desert flats at 1200-1800 m. It is only known from Cochise, Santa Cruz, and eastern Pima counties in Arizona, adjacent portions of New Mexico and Sonora, Mexico. Although its range is small, B. eludens is not rare.

Bouteloua eludens resembles B. chrondrosoides in having pubescent panicle branches, but B. eludens usually has 12-16 branches 5-11 mm long with 2-6 spikelets, whereas B. chrondrosoides usually has 3-8 branches 10-15 mm long with 8-12 spikelets per branch. Bouteloua rigidiseta is also similar to B. eludens, but differs from that species in its glume pubescence and geographic distribution, being only found in Oklahoma, Texas, and northeastern Mexico.

6.   Bouteloua chondrosioides (Kunth) Benth. ex S. Watson
Sprucetop Grama

Plants perennial; cespitose, without rhizomes or stolons. Culms (10)30-60 cm, erect, unbranched. Leaves mostly basal; sheaths mostly glabrous, margins often long-ciliate distally; ligules 0.3-0.6 mm, of hairs; blades 1-10 cm long, 1-2.5(3) mm wide, flat, glaucous, bases with papillose-based hairs on the margins, similar hairs sometimes present on either or both surfaces. Panicles 2.5-6 cm, with 3-8(10) branches; branches (8)10-15 mm, densely pubescent, with 8-12 spikelets, axes extending to 5 mm beyond the base of the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, all alike, 7-7.5 mm, with 1 bisexual and 1 rudimentary floret. Glumes evidently hairy; lower glumes 2.5-4.5 mm; upper glumes 4.5-6.5 mm; lowest lemmas 4.7-6.2 mm, hairy distally, 3-lobed, lobes unawned or shortly awned; lowest paleas 5-7.2 mm, pubescent along the veins and on the margins, bifid, veins excurrent as short awns; anthers 2.8-4 mm, yellow; upper florets rudimentary, glabrous, 3-awned, awns scabrous, sometimes arising from a short but evident awn column, central awns sometimes with a membranous margin, awns scabrous. Caryopses about 2.5 mm long, about 0.9 mm wide. 2n = 20, 22, 40.

Bouteloua chondrosoides grows on dry, rocky slopes and grassy plateaus at 200-2500 m. Its range extends from southern Arizona and western Texas to Costa Rica. It resembles B. eludens in having pubescent panicle branches, but B. eludens usually has 12-16 branches 5-11 mm long with 2-6 spikelets whereas B. chrondrosoides usually has 3-8 branches 10-15 mm long with 8-12 spikelets per branch.

7.   Bouteloua rigidiseta (Steud.) Hitchc.
Texas Grama

Plants perennial; cespitose, without rhizomes or stolons, forming dense, small clumps. Culms 10-50 cm, erect, unbranched. Sheaths smooth, striate; ligules 0.2-0.3 mm, membranous, ciliate; blades 4-12(17) cm long, 1-2 mm wide, abaxial surfaces sparsely short pubescent, bases with papillose-based hairs on the margins, similar hairs also present on both surfaces. Panicles 3-6 cm, with 6-8 branches; branches 8-16 mm, hairy, becoming more sparsely so distally, with 2-6 spikelets, axes terminating beyond the base of the terminal spikelets, apices deeply bi- or trifurcate; disarticulation at the base of the branches. Spikelets appressed, all alike, with 1 bisexual and 1-2 rudimentary florets. Glumes lanceolate, veins pubescent, apices acuminate; lower glumes 3-4 mm; upper glumes about 6 mm, pubescent over the veins, hairs about 0.7 mm, apices bilobed, awned from the sinuses; lowest lemmas 2.5-4 mm, glabrous or sparsely pubescent on the veins, 3-awned, awns wide basally, forming 3 triangular lobes, central awns flanked by 2 membranous 0.5-1.5 mm lobes; lowest paleas 4-5 mm, bilobed, veins often excurrent; second lemmas glabrous, 3-awned, awns 5-10 mm; second paleas 2-lobed, unawned; third lemmas similar to the second lemmas but smaller and without paleas. Caryopses (2) 3.5-3.7 mm. 2n = 40.

Bouteloua rigidiseta grows in grassy pastures and openings in woods, usually in clay or sandy clay soils, from near sea level to approximately 700 m. It is both widespread and abundant within its range, which extends from the southern United States to northern Mexico, but has little value as a forage grass. It is one of the earliest flowering warm season grasses. Although similar to B. eludens, B. rigidiseta differs in its geographic distribution and glume pubescence, so the two taxa are unlikely to be confused in the field.

8.   Bouteloua repens (Kunth) Scribn. & Merr.
Slender Grama

Plants perennial; cespitose, usually not dense, hard, or knotty, without rhizomes or stolons. Culms 15-65 cm, erect, geniculate, or decumbent, sometimes rooting at the lower nodes, usually branching from the aerial nodes. Sheaths glabrous or pubescent; ligules 0.2-0.3 mm, membranous, ciliate; blades 5-20 cm long, 1-5 mm wide, bases with papillose-based hairs on the margins, both surfaces glabrous or pubescent. Panicles 4-14 cm, with (3)7-12 branches; branches 10-20 mm, with 2-8 spikelets, extending 4-6 mm beyond the base of the terminal spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, all alike, with 1 bisexual and 1 staminate (rarely rudimentary) floret. Glumes glabrous, veins scabrous or strigose; lower glumes 4-7 mm; upper glumes 4-9 mm, mostly glabrous, sometimes scabrous or strigose over the veins, apices acute, unawned or awn-tipped, awns about 1 mm; lowest lemmas 4.5-8 mm, usually glabrous, rarely pubescent basally, 3-awned, awns wide basally, central awns slightly longer than the lateral awns, often flanked by 2 membranous 0.5-1.5 mm lobes; lowest paleas 6-8 mm, bilobed, often shortly 2-awned; anthers 3-5.5 mm, usually orange or yellow, occasionally red or purple; second lemmas 5.5-7 mm, glabrous, 3-awned, central awns 4-10 mm, often flanked by membranous lobes, lateral awns 2-10 mm; second paleas 4-7 mm; anthers smaller than those of the lowest florets; rachillas prolonged beyond the second florets as a short bristle. Caryopses 3-4 mm. 2n = 20, 40, 60.

Bouteloua repens grows in open, usually hilly terrain on many soil types, from sandy ocean shores to montane slopes, reaching elevations of 2500 m. Its native range extends from the southwestern United States through the Caribbean islands, Mexico, and Central America to Colombia and Venezuela.

9.   Bouteloua radicosa (E. Fourn.) Griffiths
Purple Grama

Plants perennial; cespitose, with a dense, hard, knotty base, rhizomatous, rhizomes 2-3 mm thick, with pale cataphylls; internodes 4-5 mm. Culms (40) 60-80 cm, erect, straight, unbranched. Sheaths strongly striate; ligules 0.5-1 mm, of hairs; blades mostly basal, short and firm, 2-3 mm wide, bases with papillose-based hairs on the margins. Panicles 10-15 cm, usually with 7-12 branches; branches (15)20-30 mm, deciduous, with 8-11 spikelets, apices entire; disarticulation at the base of the branches. Spikelets appressed, all alike, with 2 florets, lowest floret bisexual, upper florets pistillate, bisexual, or staminate. Glumes acuminate, glabrous; lower glumes about 4 mm; upper glumes 5-6 mm; lowest lemmas 7-8 mm, smooth, often shortly trilobed, 3-awned, awns extending from the lobes, central awns 2-3 mm, not flanked by membranous lobes, lateral awns about 1 mm; lower paleas 6-7 mm, unawned, sometimes mucronate; upper lemmas 9-10 mm, central awns 6-8 mm, lateral awns 5-6 mm; upper paleas similar to the lower paleas. Caryopses 4-5 mm long, 0.75-1 mm wide. 2n = 60.

Bouteloua radicosa grows on dry, rocky slopes at 1000-3000 m, from Arizona and southern New Mexico to southern Mexico. It has also become established in Maine, growing in disturbed habtiats, but is not common there.

Bouteloua radicosa frequently grows with B. repens at lower elevations, but extends higher than that species. Like B. repens, B. radicosa exhibits great variation in spikelet and inflorescence characters. Gould (1979) suggested that some of the variation in B. radicosa was due to hybridization with B. repens in the Flora area and B. williamsii Swallen in southern Mexico. This hypothesis has not been tested.

Bouteloua subg. Chondrosum (Desv.) A. Gray

Panicle branches 1-20, persistent, with 6-130 spikelets, terminating in a point or spikelet; spikelets usually dense and pectinate on the branches; disarticulation above the glumes.

10.   Bouteloua gracilis (Kunth) Lag. ex Griffiths
Blue Grama, Eyelash Grass

Plants perennial; usually densely cespitose, often with short, stout rhizomes. Culms 24-70 cm, not woody basally, erect, geniculate, or decumbent and rooting at the lower nodes, not branched from the aerial nodes; nodes usually 2-3, glabrous or puberulent; lower internodes glabrous. Leaves mainly basal; sheaths glabrous or sparsely hirsute; ligules 0.1-0.4 mm, of hairs, often with marginal tufts of long hairs; blades 2-12(19) cm long, 0.5-2.5 mm wide, flat to involute at maturity, hairs usually present basally. Panicles with 1-3(6) branches, these racemose on 2-8.5(12.5) cm rachises or digitate; branches 13-50(75) mm, persistent, arcuate, scabrous, without papillose-based hairs, with 40-130 spikelets, terminating in a spikelet; disarticulation above the glumes. Spikelets pectinate, with 1 bisexual and 1 rudimentary floret. Glumes mostly glabrous or scabrous, midveins sometimes with papillose-based hairs; lower glumes 1.5-3.5 mm; upper glumes 3.5-6 mm; lowest lemmas 3.5-6 mm, pubescent at least basally, 5-lobed, central and lateral lobes veined and awned, awns 1-3 mm, central awns flanked by 2 membranous lobes; lower paleas about 5 mm, shallowly bilobed, veins excurrent for less than 1 mm; rachilla internodes subtending second florets with a distal tuft of hairs; anthers 1.7-2.9 mm, yellow or purple; upper florets sterile, 0.9-3 mm, lobed almost to the base, lobes rounded, 3-awned, awns equal, 1-3 mm. Caryopses 2.5-3 mm long, about 0.5 mm wide. 2n = 20, 28, 35, 40, 42, 60, 61, 77, 84.

Bouteloua gracilis grows in pure stands in mixed prairie associations and disturbed habitats, usually on rocky or clay soils and mainly at elevations of 300-3000 m. Its native range extends from Canada to central Mexico; records from the eastern portion of the Flora represent introductions.

Bouteloua gracilis is an important native forage species and also an attractive ornamental.

11.   Bouteloua hirsuta Lag.

Plants perennial; densely or loosely cespitose, occasionally stoloniferous. Culms 15-75 cm, erect or decumbent, sometimes branched basally, sometimes branched aerially; nodes 3-6; internodes glabrous or sparsely to densely pubescent with papillose-based hairs. Leaves basal or mainly cauline; sheaths mostly glabrous, finely scabrous, or pubescent, pilose near the ligules; ligules 0.2-0.5 mm, of hairs; blades 1-30 cm long, 1-2.5 mm wide, flat to involute, papillose-based hairs often present on both surfaces, usually present on the bases of the margins. Panicles usually with 0.7-18 cm rachises bearing 1-6 branches, the branches sometimes digitate; branches 10-40 mm, persistent, straight, with 20-50 spikelets, axes extending 5-10 mm beyond base of the terminal spikelets; disarticulation above the glumes. Spikelets pectinate, green to dark purple, with 1 bisexual floret and 1-2 rudimentary florets. Glumes acuminate or awn-tipped; lower glumes 1.4-3.5 mm; upper glumes 3-6 mm, midveins with papillose-based hairs; lowest lemmas 2-4.5 mm, pubescent, 1-3-awned, central (or only) awns 0.2-2.5 mm, not flanked by membranous lobes, lateral lobes acuminate, unawned or with awns no longer than the central awn; lower paleas ovate, unawned; anthers 2-3.4 mm, cream or yellow; rachilla internodes subtending second florets glabrous or pubescent, sometimes with a distal tuft of hairs; second lemmas 0.5-2 mm, bilobed, 3-awned, awns 2-4(6) mm; third lemmas, if present, minute, membranous scales, glabrous. Caryopses 1.5-2.6 mm. 2n = 20, 40, 50, 60; numerous dysploid numbers also reported.

Bouteloua hirsuta is a widespread species, with two subspecies that frequently hybridize in areas of sympatry (Wipff and Jones 1996).

Bouteloua hirsuta Lag. subsp. hirsuta
Hairy Grama

Plants loosely or densely cespitose, sometimes stoloniferous. Culms 15-60 cm, usually decumbent and branched basally, sometimes erect, branched or unbranched from the aerial nodes; nodes usually 4-6; internodes glabrous or sparsely to densely pubescent with papillose-based hairs. Leaves basally clustered, sometimes not strongly so; sheaths glabrous or pubescent, hairs not papillose-based, sometimes scabrous. Panicles with 1-4 branches on 0.7-7.5(9.2) cm rachises or digitate; branches 1-4. Anthers 2-2.5 mm; rachilla internodes subtending second florets without a distal tuft of hairs. Caryopses 1.4-2 mm. 2n = 20, 40, 50, 60; numerous dysploid numbers also reported.

Bouteloua hirsuta subsp. hirsuta grows from the open plains to slightly shaded openings in woods and brush on well-drained, often rocky, soils at 50-300 m. It is morphologically, ecologically, and cytologically more variable than subsp. pectinata. Its range extends from North Dakota and Minnesota to central Mexico. In the northern portion of its range, it is not densely tufted and the culms are decumbent and branched; in the southwestern United States and northern Mexico, it grows in isolated, dense clumps, with erect, stout, unbranched culms and mostly basal leaves.

Bouteloua hirsuta Lag. subsp. pectinata (Feath.) Wipff & S.D. Jones
Tall Grama

Plants without rhizomes or stolons. Culms 35-75 cm, erect, densely tufted, usually unbranched; nodes 3-4; internodes glabrous. Leaves mostly basal; sheaths mostly pubescent. Panicles racemose, with (2)3-6 branches on (3)6-18 cm rachises. Anthers 2-3.2 mm; rachilla internodes subtending second florets with a distal tuft of hairs. Caryopses 1.5-2.6 mm. 2n = 20.

Bouteloua hirsuta subsp. pectinata grows in well-drained, relatively undisturbed, calcareous soils, usually on thin-soiled limestone outcrops, at 60-500 m. Its range extends from southern Oklahoma to central Texas. Although restricted in its geographic distribution, where subsp. pectinata is sympatric with subsp. hirsuta, swarms of morphologically intermediate plants are found (Wipff and Jones 1996).

12.   Bouteloua eriopoda (Torr.) Torr.
Black Grama

Plants perennial; often shortly rhizomatous, stoloniferous, stolons long, densely woolly-pubescent. Culms 20-60(75) cm, wiry, decumbent, rooting at the lower nodes; lower internodes densely woolly-pubescent. Sheaths mostly glabrous or sparsely pilose, usually pilose near the ligules; ligules 0.1-0.4 mm, of hairs; blades 2.5-6 cm long, 0.5-2 mm wide, scabrous adaxially, margins with papillose-based hairs basally. Panicles (1)2-16 cm, with (1)2-8 branches; branches 14-50 mm, persistent, densely woolly-pubescent basally, with 8-18 spikelets, axes terminating in entire, sometimes scarious apices; disarticulation above the glumes. Spikelets pectinate, with 1 bisexual floret and 1 rudimentary floret. Glumes unequal, smooth or scabrous; lower glumes 2-4.5 mm; upper glumes 4.5-8(9) mm, glabrous, scabrous, or withhairs, hairs to 0.5 mm, not papillose-based; lower lemmas 4-7 mm, pubescent basally, glabrous or sparsely puberulent distally, acuminate, central awns 0.5-4 mm, lateral awns absent or shorter than 1 mm; lower paleas acuminate, unawned; anthers 1.5-3 mm, yellow to orange; rachilla segment to second florets about 2 mm, with a distal tuft of hairs; upper florets rudimentary, an awn column terminating in 3 awns of 4-9 mm. Caryopses 2.5-3 mm. 2n = 20, 21, 28.

Boutloua eriopoda grows on dry plains, foothills, and open forested slopes, often in shrubby habitats, and also in waste ground. It is usually found between 1000-1800 m, but extends to 2500 m. Once a dominant in much of its range, under heavy grazing B. eriopoda persists only where protected by shrubs or cacti because it is highly palatable. Its range extends from the southwestern United States to northern Mexico.

13.   Bouteloua trifida Thurb. ex S. Watson
Red Grama

Plants perennial; cespitose, older plants occasionally shortly rhizomatous. Culms 5-40 cm, slender, wiry, erect or slightly geniculate at the lower nodes; lower internodes glabrous, shorter than those above. Leaves mostly basal; sheaths glabrous, sometimes scabridulous, becoming flattened, persistent; ligules 0.2-0.5 mm, of hairs; blades 0.7-8 cm long, 0.5-1.5(2) mm wide, scabridulous, margins often with papillose-based hairs basally. Panicles 3-9 cm, with 2-7 branches; branches 7-25 mm, persistent, spreading, ascending, or appressed, straight to slightly arcuate, with 8-24(32) spikelets, axes terminating in a spikelet; disarticulation above the glumes. Spikelets appressed to pectinate, reddish-purple; with 1 bisexual floret and 1 rudimentary floret. Glumes bilobed; lower glumes 1.7-3.4 mm, slightly shorter than the upper glumes, veins excurrent to 0.6 mm; upper glumes 1.9-4 mm, glabrous or pubescent, hairs not papillose-based, veins excurrent to 1 mm; lower lemmas 1.2-2.2 mm, glabrous, sparsely appressed pubescentalong the veins or densely appressed pubescent for much of their length and on the margins, trilobed, lobes veined, tapering into 3 awns, awns 2.2-6.6 mm, central awns not flanked by membranous lobes; anthers 0.2-0.4 mm, yellow; rachilla internodes glabrous; upper florets glabrous, of 3-awned, awns equal, 2-7 mm. Caryopses 0.8-1.5 mm long, 0.3-0.6 mm wide. 2n = 20.

Bouteloua trifida grows on dry open plains, shrubby hills, and rocky slopes, at 2200-2500 m. Its range extends from the southwestern United States to central Mexico. It is a drought-resistant species that is sometimes mistaken for Aristida because of its delicate, cespitose growth habit and purplish, 3-awned spikelets. Juvenile plants may also be confused with B. barbata, but that species is annual, with the central awn flanked by two membranous lobes and the lowest paleas 4-lobed and 2-awned.

Bouteloua trifida var. burkii (Scribn. ex S. Watson) Vasey ex L.H. Dewey

Panicle branches ascending to divergent, rarely appressed. Lower glumes 1.7-3.1 mm, veins excurrent for 0.05-0.2 mm, usually not exceeding the apical lobes; upper glumes 1.9-3.2 mm, veins excurrent for 0.05-0.2 mm, usually not exceeding the apical teeth; lower lemmas conspicuously appressed pubescent across the lower 2/3-4/5 and along most or all of the margins, awns 2.2-4.5 mm; anthers 0.2-0.3 mm. Caryopses 0.8-1.2 mm long, 0.5-0.6 mm wide, flat or slightly concave adaxially. 2n = 20.

Bouteloua trifida var. burkii grows in southern New Mexico, southern Texas, and adjacent Mexico.

Bouteloua trifida Thurb. ex S. Watson var. trifida

Panicle branches appressed to ascending, occasionally divergent. Lower glumes 2.2-3.4 mm, midveins excurrent for 0.1-0.6 mm; upper glumes 2.7-4 mm, midveins excurrent for 0.2-1 mm; lower lemmas glabrous or sparsely appressed pubescent along both sides of the veins, awns (3.2)4-6.6 mm; anthers 0.3-0.4 mm. Caryopses 1.3-1.5 mm long, 0.4-0.5 mm wide, grooved adaxially. 2n = unknown.

Bouteloua trifida var. trifida grows in dry plains and rocky slopes, mostly at 300-1500 m, from southern California, Nevada, and Utah to Texas and Mexico.

14.   Bouteloua kayi Warnock
Kay's Grama

Plants perennial; cespitose, without rhizomes or stolons. Culms 10-50 cm, erect; nodes glabrous; internodes glabrous, scabridulous between the veins. Leaves mostly basal; sheaths scabridulous or glabrous, sparsely pubescent basally; ligules 0.3-0.5 mm, membranous, ciliate; blades to 20 cm long, 0.5-1.5 mm wide, involute, scabridulous adaxially. Panicles 8-11 cm, with 7-20 branches; branches 15-30 mm, persistent, with (6)14-20 pedicellate spikelets, axes terminating in a spikelet; pedicels 0.6-0.8 mm; disarticulation above the glumes. Spikelets 6-8 mm, pectinate, with 1 bisexual and 1 rudimentary floret. Glumes subequal, 2.5-4 mm, glabrous, acute or bidentate, midvein sometimes excurrent as a mucro or short awn; lowest lemmas 5-7 mm, glabrous, 3-awned, awns 3-4 mm, central awns flanked by 2 membranous, acuminate, 0.4-0.6 mm lobes; lowest paleas sometimes reduced to 2 awns, awns 1-2 mm, anthers 1.2-1.3 mm, yellow; second florets glabrous, reduced to 1-3 awns, awns 3-4 mm. 2n = unknown.

Bouteloua kayi is only known from the mountainous limestone terrain along the Rio Grande River in southwestern Brewster County, Texas, at 2200-2500 m. Superficially, it resembles B. trifida.

15.   Bouteloua barbata Lag.

Plants annual or short-lived perennials; tufted, sometimes with stolons. Culms 1-75 cm, prostrate, decumbent, or erect, sometimes rooting at the lower nodes; lower internodes glabrous. Leaves basal or cauline; sheaths usually glabrous, except for tufts of long hairs on either side of the collars; ligules 0.1-1 mm, membranous, ciliate; blades 0.5-10 cm long, 0.7-4 mm wide, adaxial surfaces usually sparsely pubescent with a few papillose-based hairs basally. Panicles 0.7-25 cm, with (2)4-9(11) branches; branches 10-30 mm, persistent, straight to arcuate, glabrous, scabridulous, or with papillose-based hairs, with 20-55 spikelets, axes terminating in a well-developed spikelet; disarticulation above the glumes. Spikelets 2.5-5 mm, pectinate, with 1 bisexual and 2 rudimentary florets. Glumes unequal, glabrous, sometimes scabridulous, apices sometimes shortly bilobed, acuminate or mucronate; lower glumes 0.7-1.5 mm; upper glumes 1.5-2.5 mm, glabrous, scabrous, or strigose, hairs not papillose-based; lowest lemmas 1.7-4 mm, densely pilose, at least on the margins, 3-awned, awns 0.5-3 mm, central awns flanked by 2 membranous lobes; lowest paleas 1.5-4 mm, pubescent on the margins, 4-lobed, 2-awned, awns 1-2 mm; anthers 0.4-0.7 mm; rachilla internodes subtending second florets terminating in a dense tuft of hairs; second florets rudimentary, 1.5-4 mm, 2-lobed, lobes rounded, 3-awned, awns 0.5-4 mm; rachilla internodes subtending third florets with glabrous or puberulent apices; third florets rudimentary, flabellate, unawned. Caryopses to 1 mm. 2n = 20.

The range of Bouteloua barbata extends from the southwestern United States to southern Mexico. It has occasionally been found as far north as southern Montana, but it does not persist there and no voucher specimens exist. There are three varieties of B. barbata. The two that grow in the Flora region are often sympatric, but are usually easily distinguished in the field in this region by their growth habit. According to Gould (1979), in the southern portion of their range the differences between the two varieties are less evident, particularly on herbarium specimens. The third variety, B. barbata var. sonorae (Griffiths) Gould, is usually stoloniferous; it is known only from the states of Sonora and Sinola, Mexico.

Bouteloua barbata is often confused with juvenile plants of the perennial B. trifida, but in B. barbata the central awn is flanked by two membranous lobes and the lowest paleas are 4-lobed and 2-awned.

Bouteloua barbata Lag. var. barbata
Sixweeks Grama

Plants annual; not stoloniferous. Culms 1-35 cm, usually decumbent and geniculate, occasionally rooting at the lower nodes. Ligules 0.4-1 mm; blades 0.5-5(9) cm long, 0.7-3 mm wide. Panicles 0.7-9 cm, with (2)4-11 branches; branches 10-27 mm, scabrous, with 20-40 spikelets. 2n = 20.

Bouteloua barbata var. barbata grows in loose sands, rocky slopes, and washes, often on disturbed soils, usually at elevations below 2000 m. Its range extends from the southwestern United States to northwestern Mexico.

Bouteloua barbata var. rothrockii (Vasey) Gould
Rothrock's Grama

Plants short-lived perennials; not stoloniferous. Culms 25-60 (75) cm, stiffly erect or slightly geniculate-spreading basally; ligules 0.1-0.5 mm; blades 6-10 cm long, 1-4 mm wide. Panicles (3.5)5-25 cm, with 3-8 branches; branches 15-30 mm, scabrous, with 35-50 (55) spikelets. 2n = 40.

Bouteloua barbata var. rothrockii grows on dry slopes and sandy flats, mostly at 750-1700 m. It grows throughout the southwestern United States and Mexico, sometimes covering large areas. It used to be the most important forage grass in southern Arizona and neighboring regions.

Bouteloua barbata var. rothrockii resembles var. parryi, but can be easily distinguished from that taxon by the lack of papillose-based hairs on the keels of its upper glumes.

16.   Bouteloua simplex Lag.
Mat Grama

Plants annual. Culms 3-35 cm, usually decumbent, occasionally erect, rarely branching; internodes glabrous. Sheaths smooth, deeply striate; ligules 0.1-0.2 mm, of short hairs, sometimes with a few papillose-based hairs on either side; blades 2-8 cm long, 0.5-1.5 mm wide, flat to involute, adaxial surfaces mostly glabrous, often pilose basally. Panicles usually with only 1 branch (terminating the culm), or with 2-4 branches and subdigitate; branches 10-25(40) mm, persistent, straight, arcuate, or circular, with 30-80 spikelets, axes terminating in a reduced spikelet; disarticulation above the glumes. Spikelets pectinate, with 1 bisexual floret and 1-2 rudimentary florets. Glumes glabrous, sometimes scabrous distally, acute or acuminate; lower glumes 1.5-2.5 mm; upper glumes 3.5-5 mm; lowest lemmas 2.5-3.5 mm, pilose over the veins, 3-awned, awns stout and flattened, central awns 1-2 mm, flanked by 2 membranous lobes, lateral awns shorter than the central awns; lowest paleas obovate, unawned; rachilla internodes subtending second florets with densely pubescent apices; second florets reduced to an awn column with 3 awns of 5-6 mm; third florets, if present, flabellate scales. 2n = 20.

Bouteloua simplex grows on rocky, open slopes in grassy and open shrub vegetation at 1200-2500 m. Its native range extends from the southwestern United States through Mexico and Central America to western South America. It is adventive in Maine, where it has been grows in disturbed places, but it is not common there.

17.   Bouteloua parryi (E. Fourn.) Griffiths
Parry's Grama

Plants annual or short-lived perennials; tufted, sometimes stoloniferous. Culms 20-60 cm, erect or somewhat geniculate at the base. Leaves mostly basal; sheaths pubescent, usually with tufts of long hairs on either side of the collar; ligules 0.1-0.5 mm, of hairs; blades 1-3 cm long, 1-2.5 mm wide, margins and usually both surfaces with papillose-based hairs. Panicles 2.5-10 cm, with 4-8 branches; branches 20-35 mm, persistent, with papillose-based hairs, with 40-65 spikelets, branches terminating in a spikelet; disarticulation above the glumes. Spikelets pectinate, with 1 bisexual floret and 2 rudimentary florets. Glumes unequal; lower glumes about 2 mm, glabrous or sparsely pubescent at the base, mucronate; upper glumes 3-4 mm, keels with papillose-based hairs, apices bilobed, awned from between the teeth, awns to 0.7 mm; lowest lemmas 3-4 mm, pilose or villous proximally, 3-awned, awns 2-3 mm, central awns flanked by 2 membranous lobes; lowest paleas about 2.5 mm, 4-lobed, 2-awned; anthers 1.8-2 mm, yellow; rachilla internodes subtending second florets with densely pubescent apices; second florets lobed nearly to the base, lobes ovate, awns 2-4 mm, exceeding those of the lowest lemmas, third florets minute scales, glabrous, unawned or with a single awn. Caryopses 1.3-1.5 mm. 2n = 20.

Bouteloua parryi grows on sandy slopes and flats at elevations from near sea level to 2000 m. Its range extends from the southwestern United States to central Mexico. Plants in the Flora region belong to B. parryi (E. Fourn.) Griffiths var. parryi, which differs from B. parryi var. gentryi (Gould) Gould in comprising tufted annuals rather than stoloniferous perennials. Bouteloua parryi var. parryi resembles var. rothrockii, but differs in the papillose-based hairs on the keels of its upper glumes.

18.   Bouteloua breviseta Vasey
Gypsum Grama

Plants perennial; sometimes cespitose, sometimes rhizomatous, rhizomes 1-3 mm thick, short or elongate, scaly. Culms 20-40 cm, erect, somewhat woody at the base, branching at the base and, in late fall, sometimes at the aerial nodes; nodes usually 4-5; internodes glabrous, distal portions of the lower internodes with a thick, white, chalky bloom. Ligules 0.1-0.2 mm, of hairs; blades 1-4(7) cm long, 0.5-2 mm wide, flat basally, involute and arcuate to reflexed distally. Panicles 2-4 cm, with 1-3(4) branches; branches 15-37 mm, persistent, straight to slightly arcuate, mostly appressed, stramineous, with 30-45 spikelets, branches terminating in a reduced, needlelike, 2-5 mm spikelet; disarticulation above the glumes. Spikelets pectinate, with 1 bisexual floret and 1-2 rudimentary florets. Glumes acute to acuminate, glabrous or sparsely short-hairy, hairs not papillose-based; lower glumes 2-2.5 mm; upper glumes 2-3.5 mm; lowest lemmas 2.5-4 mm, sparsely to densely hairy, 3-awned, awns slightly shorter than the lemma bodies, central awns flanked by 2 membranous lobes; lowest paleas about 4.5mm, mostly or completely glabrous, sometimes puberulent distally, acute to acuminate, unawned, veins not excurrent; second florets about 4.5 mm, 3-awned, awns 3-5 mm; rachilla internodes subtending second florets with densely pubescent apices; third florets, if present, flabellate scales, 1-awned. Caryopses 1-1.2 mm long, about 0.4 mm wide. 2n = 20.

Bouteloua breviseta is locally abundant on gypsum soils in southeastern New Mexico and the northern portion of the Trans Pecos region in Texas. It also grows in the state of Chihuahua, Mexico. Reeder and Reeder (1980) provide an excellent discussion of B. breviseta and B. ramosa.