Plants perennial; densely cespitose, shortly rhizomatous. Culms 6-25 cm. Sheaths mostly glabrous, sparsely hispid near the throat; blades to 4 cm long, to 1 mm wide, rolled, falcate to curled, pilose or hispid. Panicles 0.5-2 cm, subcapitate; pedicels mostly shorter than or equaling the spikelets. Spikelets 4-8 mm, with 3-6 florets. Glumes glabrous or scabrous, dark purple fading to brown; lemma bodies (1.3)1.5-2 mm, with tufts of hairson the lower portion and in a transverse row below the sinus, apical teeth 1-2 mm; awns (2)3.5-5.5 mm; anthers 1.7-2.2 mm. Caryopses about 0.8 mm. 2n = 12.

Karroochloa purpurea was grown in the grass garden of the University of California, Berkeley. There is no evidence that it has become established in the Flora region.