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.
Dr. David Bogler, USDA NRCS PLANTS Database
Perennials, Terrestrial, not aquatic, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath hairy at summit, throat, or collar, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades more or less hairy, Ligule present, Ligule a fringed, ciliate, or lobed membrane, Inflorescence terminal, Inflorescence with 2 or more spikes, fascicles, glomerules, heads, or clusters per culm, Inflorescence a panicle with narrowly racemose or spicate branches, Inflorescence with 2-10 branches, Inflorescence branches 1-sided, Inflorescence branches terminating in bristle or point, Flow ers bisexual, Spikelets sessile or subsessile, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets secund, in rows on one side of rachis, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glumes 1 nerved, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma 3 nerved, Lemma body or surface hairy, Lemma apex dentate, 3-5 fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 3 awns, Lemma awn less than 1 cm long, Lemma awns straight or curved to base, Lemma margins thin, lying flat, Lemma straight, Lemma surface pilose, setose or bristly, Palea present, well developed, Palea membranous, hyaline, Palea shorter than lemma, Palea 2 nerved or 2 keeled, Stamens 3 , Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.
FNA 2003, Gould 1980
Common Name: Rothrock's grama Duration: Perennial Nativity: Native Lifeform: Graminoid General: Short lived perennial grass, stems wiry, 25-60 cm tall and in small clumps, usually stiffly erect, occasionally slightly geniculate-spreading at the base. Vegetative: Leaves glabrous or sparsely pillose-hirsute, the blades 6-10 cm long by 1-4 mm broad, often loosely involute. Inflorescence: Panicle 5-25 cm long, with 3-8 spicate branches per stem; branches scabrous, 1.5-3 cm long, 3 mm broad excluding the awns, with 35-50 spikelets; Spikelets with 1 fertile floret below and 1 rudimentary floret above; fertile lemma pubescent below with long white hairs, broad and lobed above, three nerves evident, extending from the notches as awns mostly 1.5-3 mm long; rudiment half or less as long as the fertile lemma, with rounded, somewhat inflated lobes and 3 awns. Ecology: Found on dry rocky hillsides and sandy mesas from 2,500-5,500 ft (762-1676 m); flowers August-October. Distribution: s AZ, s CA, extreme sw NM, south into MEX Notes: This species is difficult to discern from B. barbata, and is classified as a variety of B. barbata in the recent FNA treatment. Several characteristics are diagnostic: in B. rothrockii the awns are longer, the stems are usually less branched and the glumes more noticeably scaberulous rather than glabrous and shiny. The roots of B. rothrockii are often more developed to be clearly perennial, although weakly so. Very similar to B. parryi, but differs in not having papillose-based hairs on the keels of the upper glumes. An important range grass in southern Arizona, sometimes covering large areas. Ethnobotany: Unknown, other species in this genus have uses. Etymology: Bouteloua named for brothers Claudio (1774-1842) and Esteban (1776-1813) Boutelou Agraz, Spanish botanists and horticulturalists; rothrockii is named for Dr. Joseph Trimble Rothrock (1839-1922), surgeon on the Wheeler expedition of 1873-1875. Synonyms: Bouteloua barbata var. rothrockii Editor: SBuckley 2010, AHazelton 2015