Aristida ehrenbergii Trin. & Rupr.
Annual or short-lived perennial, forming erect or sprawling tufts 10-100 cm high. Leaf-blades linear, up to 20 cm long and 3 mm wide, expanded or folded. Panicle up to 30 cm long, occasionally lax, usually ± contracted about the main branches, sometimes narrow and dense. Spikelets pallid, green or purple; glumes unequal, linear-lanceolate to lanceolate, scaberulous on the keel, emarginate and mucronate or acute but never awned, the upper 5-10 mm long, the lower 1-3 mm shorter; lemma 5-13(17) mm long, sometimes no longer than the glumes but usually exceeding the upper by 1-2 mm or more, laterally compressed, convolute, scabrid on the keel or sometimes generally scaberulous on the upper part, passing into the awn without constriction or articulation; callus narrowly oblong, 0.5 mm long, obtuse; central branch of the awn 7-25 mm long, the laterals subequal or occasionally conspicuously shorter.
Fl. & Fr. Per.: March-December.
Type: Ascension Is., Osbeck (LINN).
Distribution: Pakistan (Sind, Baluchistan, Punjab, N.W.F.P., Gilgit & Kashmir); throughout the tropics.
Aristida adscensionis is a pan-tropical weed and morphologically extremely variable. There are no discontinuities between var. adscensionis and either var. pumila or var. ehrenbergii and the distinctions between them are hardly worth maintaining. The same may be said of Aristida depressa, an extreme form completely intergrading with Aristida adscensionis. The distinction between annuals and perennials in the tropics and subtropics is not always very clear and often appears to be a facultative difference of little taxonomic consequence. This is particularly true in Aristida adscensionis where the separation of perennial plants as Aristida caerulescens cannot be justified. Indeed, perennial plants, otherwise indistinguishable from typical var. ehrenbergii are seen in the Middle East.
Six-weeks Tripleawn (a North American name) is probably grazed by cattle, but nothing more definite about its economic value in Pakistan seems to be known.