Digitaria abyssinica (Hochst. ex A. Rich.) Stapf

(=Digitaria scalarum (Schweinf.) Chiov.)

Family: Poaceae,  Tribe: Paniceae

Common names:  African couchgrass, fingergrass

Disseminule:  Spikelet; disarticulation below the glumes.

Description

Spikelets of 1 fertile floret and 1 basal sterile lemma. Spikelets ovate-elliptic, dorsally compressed, plano-convex, 1.5-2.5 mm long, 0.8-1 mm wide, completely glabrous. Pedicel segment often persistent. Glumes 2, dissimilar; lower glume absent or reduced, hyaline; upper glume membranous, slightly shorter than to as long as spikelet. Sterile lemma similar in appearance to upper glume, as long as spikelet. Fertile floret brown at maturity, fertile lemma cartilaginous, shorter than to as long as spikelet, with flat margins enclosing much of palea, faintly muricate.

Identification remarks

Fertile lemmas in the genus Digitaria are flat and thinner at the margins. Distinguishing characteristics of Digitaria abyssinica include its glabrous, unequally pedicelled spikelets and fertile floret that is brown at maturity. See

Digitaria velutina (Forssk.) P. Beauv.

Distribution

Widespread in tropical Africa, including South Africa and Madagascar; also Sri Lanka, Hawaii.

Native to Eastern Africa.

Habitat

Moist, shady places, roadsides.

General information

Digitaria abyssinica is a perennial rhizomatous grass, up to 60 cm tall. It is reported to be the most troublesome weed in Eastern Africa, invading major crops such as coffee and cotton. Eradication is difficult because propagation is primarily by rhizomes. Cultivation creates rhizome fragments, which can generate new plants. The grass is eaten by livestock, but is not productive enough to be used as a pasture grass.

A, Spikelet in ventral view showing lower glume and sterile lemma; B, spikelet in dorsal view showing upper glume; C, floret in ventral view showing palea and margins of lemma; D, floret in dorsal view showing lemma

A, Spikelet in ventral view; B, spikelet in dorsal view; C, floret in ventral view; D, floret in dorsal view; E, caryopsis in ventral view; E, caryopsis in dorsal view

drawing by Lynda E. Chandler

Caryopsis in dorsal view

photo by Mark Thurmond

Inflorescence

photo on right by Mark Thurmond