Plants perennial, extensively rhizomatous. Culms to 10 m tall, 1.5-2.5 cm in diam., erect, often woody in texture. Leaf-sheaths,= glabrous, green; ligules 0.5-1 mm, ciliolate; blades 30-80 cm long, 12-40 mm wide, erect-ascending, glabrous, lower surfaces scabrous at least distally, tips stiff, attenuate (occasionally almost smooth or filiform). Panicles 30-50 cm long, 10-20 cm wide, the lowest node often with a whorl of many-branches; branches without spikelets on the lower portion. Spikelets 9-12 mm long; rhachilla-hairs 4-7 mm long, rather sparse; lower glumes just over half as long as the upper; upper glumes 3.5-6 mm long, narrowly to very narrowly elliptic, acute to subacute; lowest lemmas 7-12 mm long, very narrowly elliptic; other lemmas 8.5-11 mm long, very narrowly lanceolate, tips long attenuate.
2n = 24, 36, 38, 48.
Phragmites karka grows in Africa, from Pakistan through China to Japan, in northern Australia, and many Pacific Islands.