sixweeks threeawn, more...
[Aristida adscensionis f. modestina Hack., more]
Kelly W. Allred. 2007. Aristida, published in Barkworth et al. (eds.), Flora of North America vol. 25
Plants short- to long-lived annuals. Culms (3)10-50(80) cm, often highly branched above the base. Leaves cauline, glabrous; sheaths shorter than the internodes, not disintegrating into threadlike fibers; ligules 0.4-1 mm; blades 2-14 cm long, 1-2.5 mm wide, flat to involute. Inflorescences panicles, 5-15(20) cm long, 0.5-3 cm wide, often interrupted below; nodes glabrous or with straight, less than 0.5 mm hairs; primary branches 1-4 cm, erect to ascending, without axillary pulvini, with 3-8 spikelets. Spikelets crowded. Glumes unequal, 1-veined, acuminate; lower glumes 4-8 mm; upper glumes 6-11 mm; calluses 0.5-0.8 mm; lemmas 6-9 mm, slightly keeled, midveins scabrous, junction with the awns not evident; awns not disarticulating at maturity, flattened and straight to somewhat curved at the base, central rib flanked by equally wide pale wings; central awns 7-15(20) mm; lateral awns somewhat shorter, occasionally only 1-2 mm; anthers 3, 0.3-0.7 mm. 2n = 22.
Aristida adscensionis grows in waste ground, along roadsides, and on degraded rangelands and dry hillsides, often in sandy soils. It is associated with woodland, prairie, and desert shrub communities. Its range extends from the United States south through Mexico and Central America to South America.
Because A. adscensionis is highly variable in height, panicle size, and awn development, several varieties have been described. None are recognized here because most of the variation appears to be environmentally induced.
Plant: Annual grass 10-30 cm; inflorescence narrow and spikelike, often with a purplish color; spikelets with one floret, unequal glumes; lemma elongated into a twisted awn column, apex bearing three awns 5-15 mm long. Notes: This is a very widespread species in the drier areas of the world. Becauseý of the numerous morphological forms many infraspecific names have been proposed. However, many of the distinctive forms are connected by intergrading forms, and for this reason no infraspecific taxa are recognized in this Catalogue pending a world-wide revision of this taxon. References: Delta World Grasses
A chiefly tropical sp. with the awns flat at the base, the central one 8-15 mm, the first glume half to two-thirds as long as the second, is rarely adventive in our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
©The New York Botanical Garden. All rights reserved. Used by permission.
FNA 2003, Gould 1980
Common Name: sixweeks threeawn Duration: Annual Nativity: Native Lifeform: Graminoid General: Small tufted annual, erect stems 10-50 cm, highly branched above base sheaths have papery margin, shorter than internodes. Vegetative: Blades flat, 2-14 cm long, 1-2.5 mm wide, flat to involute, 3-4 veins on each side of midrib, glandular hairs at base of blade; ligule ciliate, 0.5 mm, some long hairs 2-3 mm; collar with hairy margin, glandular. Inflorescence: Dense panicles, contracted, often interrupted, 5-15 cm long with spikelets aggregated on short, widely-spaced branches, glumes unequal, lower glume 1-nerved, 5-8 mm, rough-textured on nerve, broad, upper glume 8-11 mm; lemma 6-9 mm long, pubescent on callus, rough-textured on slightly keeled midrib, 3 awns, 7-15(20) mm long, flattened at base, lateral awns slightly shorter. Ecology: Found on dry sandy or rocky slopes, deserts, dry mesas, often on disturbed soils from 1,000-6,000 ft (305-1830 m); flowers June-October. Distribution: Much of the western US: c and s CA north through NV west to KS and NE; south to s MEX. Notes: If you are looking at an annual Aristida, chances are it's this species. Distinguished by being an annual, erect three-awn grass, sometimes bunched at the base or only with a few culms branched above the base. The panicles are condensed with appressed branches and spikelets with two awns shorter than the third (sometimes only slightly so). It can form dense stands after summer rains and is generally common in the southwest deserts. Provides good forage, especially during summer. The only other annual three-awn in the Southwest is A. oligantha, which has more veins (3-7) on its glumes and sparsely flowered panicles with longer (>2 cm), more divergent awns. Ethnobotany: Unknown Etymology: Aristida is from the Latin arista for awn, while adscensionis is thought to refer to Ascension Island. Synonyms: Aristida adscensionis var. abortiva, A. adscensionis var. modesta, A. fasciculata Editor: SBuckley 2010, FSCoburn 2014, AHazelton 2015
This project made possible by National Science Foundation Award 1410069