Pennisetum macrourum

Name and classification

Pennisetum macrourum Trin.
Family Poaceae, Tribe Paniceae

Common names

African feathergrass, waterside reed

Disseminule

spikelet (usually single, occasionally in clusters) enclosed by fascicle consisting of bristles; disarticulation below fascicle

Description

Fascicle consists of unfused, antrorsely scabrous bristles; outer bristles number 15–20 and are 2.5–8 mm long; inner bristles number 8–10 and are 4–9 mm long; primary bristle solitary, conspicuously longer than other bristles, to 20 mm. Spikelets usually solitary, sessile or pedicellate (pedicels to 0.2 mm long), lanceolate, dorsally compressed; 2–8 mm long, ca. 1.2 mm wide; consisting of 1 fertile floret and 1 basal sterile floret (usually just the lemma). Glumes small, hyaline; lower glume absent or scale-like (to 1.4 mm long); upper glume 0.8–2 mm long. Sterile lemma membranous, 3–5(7) nerved, up to length of spikelet. Fertile lemma 3–6.8 mm long, membranous, thicker than glumes, 5–7-nerved, surface rough. Caryopsis oblong-obovate, dorsally compressed, golden; embryo up to to 3/4 length of caryopsis.

Identification considerations

Pennisetum macrourum spikelets solitary or in clusters in the fascicle. See

Pennisetum clandestinum Hochst. ex Chiov.

Pennisetum pedicellatum Trin.

Pennisetum polystachion (L.) Schultes.

Distribution

South Africa and much of tropical Africa, Australia, New Zealand, Ascension Island and St. Helena in South Atlantic Ocean, United States

native to tropical Africa and South Africa

Habitat

subhumid warm-temperate regions, wet or swampy places, along streams, roadsides, hillsides

General information

Pennisetum macrourum is a perennial grass up to 200 cm tall, with rhizomes to a depth of 30 cm. Dense clumps may form through extensive rhizome growth. These clumps may eventually eliminate other plant species and prevent access to water. Cultivation may help spread the species, as rhizome fragments can generate roots and shoots at nodes. Disseminules may be spread by water or wind, or by clinging to animal fur. This grass has been used ornamentally as a landscape plant.

spikelets singly and in clusters, each subtended by a fascicle of bristles

spikelets singly and in clusters, each subtended by a fascicle of bristles

ventral view of fertile floret showing margins of lemma enclosing palea (left); spikelet subtended by primary bristle showing upper glume and fertile lemma (right).

ventral view of fertile floret showing margins of lemma enclosing palea (left); spikelet subtended by primary bristle showing upper glume and fertile lemma (right).

caryopses in ventral view (left) and dorsal view (right)

caryopses in ventral view (left) and dorsal view (right)

A, spikelet cluster in fascicle; B, spikelet showing lower glume and sterile lemma; C, spikelet showing upper glume and fertile lemma; D, floret; E, caryopsis in ventral view; F, caryopsis in dorsal view; drawing by Lynda E. Chandler

A, spikelet cluster in fascicle; B, spikelet showing lower glume and sterile lemma; C, spikelet showing upper glume and fertile lemma; D, floret; E, caryopsis in ventral view; F, caryopsis in dorsal view; drawing by Lynda E. Chandler