Plants annual or perennial; cespitose from a hard, knotty base. Culms
30-200 cm, erect, branching; nodes glabrous. Sheaths glabrous, margins
ciliate; ligules 1.5-2.7 mm; blades 15-55 cm long, 4-18 mm wide,
flat, glabrous or pubescent. Panicles terminal, 10-25 cm long, 15-30 mm
wide, fully exerted from the sheaths, erect to drooping, white, yellow, light
brown, or pink to deep purple; rachises terete, scabrous. Fascicles
33-45 per cm, disarticulating at maturity; fascicles axes 0.2-0.5 mm, with
1 spikelet; outer bristles 13-30, 1.3-5 mm, scabrous; inner bristles
6-14, 4.3-11.5 mm, long ciliate; primary bristles 14-25 mm, long-ciliate,
noticeably longer than the other bristles. Spikelets 3-4.5 mm, sessile;
lower glumes absent or to 2 mm, veinless; upper glumes 3-4.5 mm,
glabrous, 5-7-veined, 3-lobed; lower florets sterile or staminate; lower
lemmas 3-3.9 mm, 5-7-veined, apices lobed; lower paleas 2.9-3.7 mm;
anthers absent or 1.7-2 mm; upper florets disarticulating at maturity;
upper lemmas 1.7-3 mm, coriaceous, shiny, 5-veined, apices ciliate; anthers
1.3-2.1 mm. Caryopses about 1.7 mm, concealed by the lemma and palea at
maturity. 2n = 18, 36, 45, 48, 52, 53, 54, 56, 78.
Pennisetum polystachion is a polymorphic, weedy African species that has
become established in the tropics and subtropics, including Florida. The U.S.
Department of Agriculture considers it a noxious weed. Only Pennisetum polystachion
subsp. setosum (Sw.) Brunken has
been found in the Flora region. It differs from P. polystachion
(L.) Schult. subsp. polystachion
as indicated in the key below.