Violet Crabgrass

This widespread, weedy species is closely related to Digitaria longiflora, and there is some overlap between the two. Digitaria violas-cens tends to be tufted rather than stoloniferous, with 3 or more longer racemes, angular, scabrous pedicels, a shorter, 3-veined upper glume, and distinctive, blackish fruits.

Digitaria violascens is closely allied to Digitaria longiflora. The two species intergrade to some extent, and there are no infallible characters for separating them. Typically Digitaria violascens is a more erect plant with 3 or more slender racemes, scabrid pedicels, a smaller upper glume (commonly 3-nerved and noticeably shorter than the spikelet) and a dark-coloured fruit.

Annuals; culm tufted, 20-50 cm tall. Blade less than 12 cm long, 3-6 mm wide; sheath mostly shorter than internode; ligule truncate, membranaceous, erose, brownish, 1-1.5 mm long. Racemes 3-9, 4-14 cm long, slender; rachis glabrous, flat, serrately winged, ca. 0.6 mm wide; pedicel terete to slightly flattened, one ca. 2 mm long and other only 0.5 mm long. Spikelets paired, elliptic, minutely covered with verrucose hairs, ca. 1.5 mm long; lower glume absent; upper glume more than 3/4 as long as spikelet, 3-veined, interveins white hairy; lower lemma as long as spikelet, veins distinct; upper lemma acute, dark brown or blackish purple at maturity.

Annual. Culms loosely tufted, infrequently shortly stoloniferous, 20–60 cm tall. Leaf sheaths glabrous or pilose, especially at mouth; leaf blades linear-lanceolate, 5–15 × 0.2–0.6 cm, scabrous, glabrous or adaxial surface pilose at base, apex acute; ligule 1–2 mm. Inflorescence subdigitate; racemes (2–)3–7(–10), ascending, 3–12 cm; spikelets ternate; rachis ribbonlike, winged, 0.5–0.8 mm broad, midrib low and rounded, margins serrate; pedicels angular, scabrous, with discoid tips. Spikelets elliptic-oblong, 1.4–1.9(–2.5) mm, hairs verrucose, sometimes hook-tipped; lower glume absent; upper glume lanceolate, slightly shorter than spikelet, 3(–5)-veined, intervein spaces and margins appressed-pubescent; lower lemma as long as spikelet, 5–7-veined, intervein spaces and margins pubescent, but usually glabrous flanking the middle vein; upper lemma dark brown or purplish black at maturity. Anthers 0.3–0.6 mm. Fl. and fr. Jul–Nov. 2n = 36.

Annual; culms 20-60 cm high, erect or geniculately ascending, seldom stoloniferous. Leaf-blades 3-25 cm long, 2-7 mm wide. Inflorescence composed of (2-) 3-6(-9) subdigitate racemes; racemes 3-14 cm long, the spikelets ternate on a ribbon-like winged rhachis with low rounded midrib; pedicels terete to ± flattened and winged, scabrid, with discoid or cupuliform tip. Spikelets elliptic, 1.2-2 mm long; lower glume an obscure hyaline rim; upper glume four-fifths to almost as long as the spikelet, 3(-5)-nerved, with, short appressed verrucose hairs between the nerves; lower lemma as long as the spikelet, 5-7-nerved, pubescent (often obscurely so) with verrucose hairs; fruit ellipsoid, dark brown to almost black.

Tropical regions of both hemispheres.

Tropical regions of both hemispheres. Taiwan, weedy in sunny places.

Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Qinghai, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Bhutan, India, Indonesia, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Sri Lanka, Thailand, Vietnam; Australia, South America].

Distribution: Pakistan (Punjab, N.W.F.P. & Gilgit); tropical Asia and America; introduced and naturalised in Tanzania.

1200-1800 m

Fl. & Fr. Per: (May-) July-August.

Hillsides, roadsides, weedy places; ca. 1000 m.

Digitaria chinensis (Nees) A. Camus (1923), not Hornemann (1819); D. pertenuis Buse; D. thwaitesii (Hackel) Henrard var. tonkinensis Henrard; D. violascens (Link) var. villosa Keng; Panicum steudelianum Domin; P. violascens (Link) Kunth; Paspalum chinense Nees; P. minutiflorum Steudel (1853), not Desvaux (1831); Syntherisma chinensis (Nees) Hitchcock.