Setaria rubiginosa (Steud.) Miq.
Loosely tufted annual; culms 5-130 cm high, ascending. Leaf-blades linear, 3-30 cm long, 2-10 mm wide. Panicle spiciform, cylindrical, 1-10(20) cm long, the rhachis tomentellus; bristles 3-12 mm long, slender, commonly fulvous. Spikelets ovate, 1.5-3.5 mm long; both glumes one-third to two-thirds the length of the spikelet; lower floret male or sterile, its palea almost as long as the lemma; upper lemma rugose to corrugate, rarely almost smooth.
Fl & Fr. Per.: June-October.
Type: locality unknown but probably France or North Africa, Desfontaines(P?).
Distribution: Pakistan (Sind, Baluchistan, Punjab, N.W.F.P., Gilgit & Kashmir); tropical and warm temperate regions of the Old World; introduced to North America.
Panicum pumila is a polymorphic weed segregating into regional populations. These overlap to such an extent that the recognition of more than one species cannot be upheld, though there may be a case for distinguishing between tropical and Mediterranean populations at infra-specific level (see Clayton in Kew Bull. 33:501. 1979). Much argument has been devoted to the nomenclature of this species (summarised by Terrell in Taxon 25:297-304. 1976), but it now seems that the commonly used name Panicum glauca should be referred to Pennisetum.
Panicum pumila is closely related to the caespitose perennial Panicum sphacelata (K. Schum.) Moss, and specimens lacking their basal parts are often indistinguishable. The latter is a native of tropical and South Africa introduced to India (but not, thus far, to Pakistan) as a fodder grass. Panicum pumila is even more difficult to separate from another introduction, Panicum gracilis Kunth (Panicum geniculata auct. non (Willd.) P. Beauv.), which occurs in America and tropical Asia. This is a short-lived perennial, commonly with short knotty rhizomes bearing dormant buds, though the perennial habit is usually not very obvious.