East Indian Crabgrass

This coarse, weedy species is widespread in warm parts of Asia. Spikelet pubescence is very variable, as in most members of the complex around Digitaria ciliaris, but the species can be readily distinguished by the lack of a lower glume and the presence of only a very short upper glume.

Specimens have sometimes been misidentified as Digitaria corymbosa Merrill. True D. corymbosa is a synonym of D. compacta (Roemer & Schultes) Veldkamp from India.

Specimens with glassy bristles on one or both spikelets of a pair are sometimes segregated as var. calliblepharata but the character does not seem to be of much taxonomic consequence in Digitaria.

Annuals; culm to 1 m high or more, decumbent, branching and rooting at lower nodes. Blade 5-15 cm, rarely to 30 cm long, 5-10 mm wide, scabrous and undulate on margins; sheath mostly shorter than internode, often papillose-pilose; ligule 2-4 mm long, membranaceous. Inflorescence in digitate racemes, racemes 6-15, 7-14 cm long; rachis ridged, scabrous on wing-margins, ca. 0.6 mm wide; pedicel ridged or norrowly winged. Spikelet more or less pubescent, lanceolate-elliptic, 2.5-3 mm long; lower glume absent or reduced to a minute veinless scale; lower lemma equaling or slightly exceeding upper lemma, 5-7-veined; upper lemma slightly coriaceous, pale.

Annual. Culms tufted, decumbent, branching and rooting at lower nodes, 30–100 cm tall. Leaf sheaths glabrous or papillose-pilose; leaf blades linear-lanceolate, 5–20 × 0.3–1 cm, glabrous on both surfaces, papillose-pilose at base, base subrounded, apex acuminate; ligule 1–2 mm. Inflorescence digitate or subdigitate, axis 1–4 cm; racemes 5–12, stiff, 5–15 cm; spikelets paired, imbricate by about 2/3 their length; rachis triquetrous, narrowly winged, ca. 0.6 mm broad, margins scabrous. Spikelets narrowly lanceolate-oblong, 2–2.5(–3) mm, acute; lower glume absent or a minute rim; upper glume up to 1/3 as long as spikelet, 1–3-veined, margins ciliate, apex villous with overtopping hairs; lower lemma as long as spikelet, 5–7-veined, veins evenly spaced or with a wider interspace flanking the midvein, lateral intervein spaces and margins appressed pubescent to villous, rarely ciliate or setose; upper lemma yellowish to gray, subequaling lower lemma, acuminate. Fl. and fr. Jun–Nov. 2n = 27, 36, 54, 72.

Annual; culms 20-80 cm high, geniculately ascending from a decumbent base. Leaf-blades broadly linear to lanceolate, 3-25 cm long, 3-12 mm wide. Inflorescence composed of 3-15 racemes arranged on a common axis 1-6 cm long, or digitate in the smaller plants; racemes 4-15 cm long, the spikelets binate and overlapping by ± two-thirds their length on a narrowly winged rhachis with triquetrous midrib, this sometimes bearing a few long glistening hairs; pedicels triquetrous with truncate tip. Spikelets lanceolate to elliptic-lanceolate, 2-3.5 mm long; lower glume absent or very obscure; upper glume one-eighth to one-third (rarely up to half) as long as the spikelet, oblong or triangular, nerveless to sub-3-nerved; lower lemma as long as the spikelet, 7-nerved, the nerves evenly spaced or with a wide central interspace, appressedly or silky pubescent, rarely with a ciliate frill, very rarely with stiff bristles; fruit lanceolate, grey to yellowish-brown.

Himalaya, India, Burma, Thailand, Indo-China.

Tropical Asia. Taiwan, in open waste places throughout the Island.

Distribution: Pakistan (Punjab & Kashmir); Tanzania, Mauritius and the Seychelles; through Asia to the Pacific Islands.

700 m

Fl. & Fr. Per.: September.

Moist slopes, stream banks, roadsides and weedy places. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, Yunnan [Bangladesh, Bhutan, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Thailand, Vietnam; E Africa (Tanzania), Australia, Indian Ocean Islands (Seychelles), Madagascar, Pacific Islands].

Digitaria hainanensis Hitchcock ex Keng; Digitaria micro-bachne (J. Presl) Henrard; D. microstachya Henrard; D. pruriens (Fischer ex Trinius) Buse; D. sanguinalis (Linnaeus) Scopoli var. pruriens (Fischer ex Trinius) Prain; Panicum microbachne J. Presl; P. pruriens Fischer ex Trinius; P. san-guinale Linnaeus var. microbachne (J. Presl) Hackel; Syn-therisma microbachne (J. Presl) Hitchcock.