Plants perennial, forming loose clumps. Culms 20-90 cm, decumbent, often rooting from the lower nodes; nodes antrorsely pilose; internodes glabrous. Leaves crowded towards the base; sheaths open, sparsely to densely pilose; ligules about 1 mm, membranous; blades 4-15 cm long, 3-8 mm wide, pilose on both surfaces. Inflorescence units with 2 rames; rames 3-5 cm long, 4-5 mm wide; internodes 3-4 mm long, 0.5-0.7 mm wide, slightly triquetrous. Sessile spikelets 4-5 mm long, 1.2-1.5 mm wide; calluses strigose; lower glumes coriaceous below, thickly membranous above, rough but not rugose, 5-7-veined, 2-keeled, keels narrowly winged; upper glumes 1-keeled, keels winged distally, awned, awns 1-1.5 cm; anthers 2-2.5 mm. Pedicels 2.5-3.5 mm, ciliate on the edges. Pedicellate spikelets slightly smaller than the sessile spikelets. 2n = 36.

Reed (1964) reported finding Ischaemum indicum growing on chrome ore piles in Canton, Maryland. This reported introduction has not been verified.

Plants highly stoloniferous. Culms 10-40 cm, decumbent, rooting at the lower nodes, erect portions 10-20 cm; nodes pubescent; internodes glabrous. Leaves cauline, often purplish; sheaths keeled, pubescent basally and sometimes sparsely so distally, margins ciliate; ligules 0.2-0.5 mm, truncate; blades 0.5-7 cm long, 1-7 mm wide, flat, pubescent. Rames 2-3 cm; internodes 2-3 mm, flat, ciliate on the edges and distally. Sessile spikelets 3-4 mm, ovate, pilose, brown or yellow-brown; calluses blunt; glumes concealing the floret; lower glumes 2-3 mm; lemmas about 1 mm; awns 4-12 mm, exserted, geniculate, twisted below the bend, brown. Pedicels 4-4.5 mm, slender, free of the rame axes. Pedicellate spikelets similar to the sessile spikelets or somewhat smaller, sometimes staminate. Caryopses 1.5-1.8 mm. 2n = 20.

Polytrias amaura is native to southeastern Asia. It used as a lawn grass in tropical and subtropical regions, including Florida. It gives a purplish cast to a lawn.