Digitaria didactyla Willd.

Global description

Digitaria didactyla is a small vivacious grass with elongated stolons and rhizomes. The culms are first prostrate, then erect at the inflorescence, with glabrous nodes. The sheaths are smooth or scabrous and glabrous on the surface. The ligule is membranous. The leaf blade is short, lanceolate, glaucous, smooth and glabrous on the surface, scabrous on the margin. The inflorescence is composed of 2 to 3 unilateral, paired or digitate linear racemes. The spikelets are lanceolate or oblong and compressed dorsally on the rachis of the raceme.

First leaves

The prefoliation is rolled.

General habit

Digitaria didactyla is a small vivacious grass with stolons and rhizomes, whose culms are spread out on the ground, forming a carpet.

Underground system

Elongated, knotty rhizomes and runners, rooting from the lower nodes. Fasciculate roots.

Culm

Culms are prostrate, then erect, reaching 15-30 cm long, cylindrical in cross-section. The nodes are brown and hairless.

Leaf

The sheath is smooth or scabrous and hairless on the surface. The ligule is membranous, 8 mm high. The blade is lanceolate, 3-6(-10) cm long and 3-6 mm wide, glaucous, smooth and glabrous on the surface, with a scabrous margin. The base is straight and the apex is acute wedge-shaped.

Inflorescence

The inflorescence consists of 2-3(-4) geminate or digitate racemes at the top of the inflorescence axis. They are 3-10 cm long. The rachis is 0.6 mm wide, angular, smooth on the surface, scabrous on the edges, wingless or narrowly winged, with a sharp-edged midrib.

Spikelet

Spikelets are geminate, one subsessile, the other borne on a 2.5 mm long pedicel, cylindrical or angular, scabrous, widened at the tip. Each spikelet consists of 1 basal sterile floret and 1 upper fertile floret, without rachillet extension. The spikelets are (2-)2.2-2.7 mm long. They are lanceolate or oblong, dorsally compressed. The lower glume is 0.1 times the length of the spikelet. It is oval, membranous, truncated at the apex, without a carina or vein. The upper glume is 0.33-0.5 times the length of the spikelet. It is oval, membranous, pubescent on the surface, acute at the apex, 3-veined and without a carina.

The basal sterile floret has a lemma of the same length as the spikelet, lanceolate, membranous, smooth or scabrous, pubescent, acute at the apex, with 7 rough veins. The palea is absent or insignificant.  The upper fertile floret has a lemma 2-2.7 mm long, lanceolate, cartilaginous, much thinner at the margin, yellow or light brown, without a carina. It is acute at the apex, flattened at the margins, covering most of the cartilaginous palea.

Fruit

At maturity the spikelet is falling entire. 

Origin

Digitaria didactyla is native to East Africa (Malawi, Mozambique) and the southwestern islands of the Indian Ocean (Madagascar, Seychelles, Reunion, Mauritius).

Worldwide distribution

Species introduced as a turf plant in different regions: USA (Florida) South America (Suriname, Guyana), South East Asia (India, Indonesia, Malaysia, New Guinea, Vietnam), Australia and Pacific Islands (Fiji, Tonga).

https://www.gbif.org/species/5289960