Violet Crab Grass

Nile region (Nubia).

Native to tropical Asia and tropical America, occasionally introduced elsewhere as a weed.

Introduced weed.

Annual.

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.

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.

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.

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.

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].

Tropical regions of both hemispheres.

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.

Annuals, Terrestrial, not aquatic, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems mat or turf forming, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Le af sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath hairy, hispid or prickly, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence a panicle with digitately arranged spicate branches, Inflorescence with 2-10 branches, Inflorescence branches 1-sided, Lower panicle branches whorled, Rachis winged, Rachis angular, Flowers bisexual, Spikelets pedicellate, Spikelets dorsally compressed or terete, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets with 2 florets, Spikelet with 1 fertile floret and 1-2 sterile florets, Spikelets 3 per node, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating below the glumes, Spikelets secund, in rows on one s ide of rachis, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 1 clearly present, the other greatly reduced or absent, Glumes 2 clearly present, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glume surface hairy, villous or pilose, Glumes 3 nerved, Glumes 4-7 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 5-7 nerved, Lemma apex acute or acuminate, Lemma awnless, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea membranous, hyaline, Palea about equal to lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.