Plants usually perennial; herbaceous, usually cespitose, occasionally rhizomatous. Culms 10-150 cm, not woody, sometimes branched above the base; internodes usually pith-filled, sometimes hollow. Leaves sometimes predominantly basal, sometimes predominantly cauline; sheaths open; auricleslacking; ligules of hairs or very shortly membranous and long-ciliate, the 2 types generally indistinguishable. Inflorescences terminal, usually panicles, sometimes racemes, occasionally spikes; primary branches without axillary pulvini and usually appressed to ascending, or with axillary pulvini and ascending to strongly divergent or divaricate. Spikelets with 1 floret; rachillas not prolonged beyond the florets; disarticulation above the glumes. Glumes often longer than the florets, thin, usually 1-3-veined, acute to acuminate; florets terete or weakly laterally compressed; calluses well-developed, hirsute; lemmas fusiform, 3-veined, convolute, usually glabrous or scabridulous, usually enclosing the palea at maturity, usually with 3 terminal awns, lateral awns reduced or obsolete in some species, lemma apices sometimes narrowed to a straight or twisted beak below the awns; awnsascending to spreading, usually straight, bases sometimes twisted together into a column or the bases of the individual awns coiled, twisted, or otherwise contorted, occasionally disarticulating at maturity; paleas shorter than the lemmas, 2-veined, occasionally absent; anthers 1 or 3. Caryopsesfusiform; hila linear. x = 11, 12. Name from the Latin arista, awn.
Aristida is a tropical to warm-temperate genus of 250-300 species. It grows throughout the world in dry grasslands and savannahs, sandy woodlands, arid deserts, and open, weedy habitats and on rocky slopes and mesas. All 29 species in this treatment are native to the Flora region.
The divergent awns aid in wind and animal transportation of the florets and, by holding the florets and the caryopses they contain at an angle to the ground, in establishment. The presence of Aristida frequently indicates soil disturbance or abuse. Although generally poor forage grasses and, because of the calluses, potentially harmful to grazing animals, some species of Aristida are an important source of spring forage on western rangelands. Quail and small mammals eat small amounts of the seed.
SELECTED REFERENCESAllred, K.W. 1984. Morphologic variation and classification of the North American Aristida purpurea complex (Gramineae). Brittonia 36:382-395; Allred, K.W. 1984, 1985, 1986. Studies in the genus Aristida (Gramineae) of the southeastern United States. Rhodora 86:73-77; 87:137-145, 145-155; 88:367-387;Henrard, J.T. 1926, 1927, 1928, 1933. A critical revision of the genus Aristida. Meded. Rijks-Herb. 54:1-701; 55C:703-747; Henrard, J.T. 1929, 1933. A monograph of the genus Aristida. Meded. Rijks-Herb. 58:1-325; Kesler, T.R. 2000. A taxonomic reevaluation of Aristida stricta (Poaceae) using anatomy and morphology. Master's thesis. Florida State University, Tallahassee, Florida, U.S.A. 33 pp.; Peet, R.K. 1993. A taxonomic study of Aristida stricta and A. beyrichiana. Rhodora 95:25-37; Reeder, J.R. and R.S. Felger. 1989. The Aristida californica-glabrata complex (Gramineae). Madroño 36:187-197; Trent, J.S. and K.W. Allred. 1990. A taxonomic comparison of Aristida ternipes and Aristida hamulosa (Gramineae). Sida 14:251-261; Vaughn, J.M. 1981. Systematics of Aristida dichotoma, basiramea, and curtissii(Poaceae). Master's thesis. University of Oklahoma, Norman, Oklahoma, U.S.A. 38 pp.; Walters, T.E.. D.S. Decker-Walters, and D.R. Gordon. 1994. Restoration considerations for wiregrass (Aristida stricta): Allozymic diversity of populations. Conservation Biol. 8:581-585.
T.A. Cope (1993) Poaceae Flora of Somalia 4: 148-270
Plants annual or perennial. Leaves: blades flat or rolled. Glumes 1(-5)-veined; floret calluses obtuse to pungent' lemmas convolute or involute; awns with or without a column, persistent or deciduous, glabrous, flat or terete, sometimes the lateral awns reduced to more or less suppressed.
Aristida includes about 250 species. It is most abundant in the tropics and subtropics. The Flora of Somalia reports 18 species from Somaliland and Somalia.
