Oldfield Threeawn , Prairie Threeawn

Aristida oligantha



Oldfield Threeawn grows in tufts and is much branched at the base and nodes (freely branched above the base with age). The base is woolly. Leaf blades are mainly cauline growing to 25 cm by 5 mm. Leaf-sheaths are smooth and rounded on the back. The open panicle, which can be from 2/3 to ¾ of the culm, is few-flowered. Purplish spikelets are widely spaced. Spikelet lemmas have long, spreading awns of about equal length reaching 2 inches or 5.5 cm. The three-veined lemma is also long, reaching 6 to 28 mm. The first and second glumes persist after the seed disperses.  Oldfield Threeawn is a solitary, annual, warm-season, native with wiry culms ranging from 12 to 24 inches or 30 to 60 cm tall.  Poor grazing for both livestock and wildlife. Mature seeds create problems in wool and irritate the eyes of livestock. It also may have allelopathic effects on other plants. 


An abundant, weedy species of waste places; common on sandy soils but can grow on clays. Grows in upland areas and increases in disturbed and overgrazed areas. Plant density is controlled by the amount of bare ground and rainfall in spring and early summer. USDA maps suggest it is least common in the Panhandle, Trans-Pecos, and extreme South Texas.