Trailing Crab Grass

This species is related to Digitaria ciliaris, but differs in its slender, trailing habit, fewer digitate racemes with smooth-edged rachis, and narrow spikelets with contiguous lateral veins in the lower lemma, which thereby appears 3-veined.

This species is used for forage.

Digitaria radicosa is related to Digitaria ciliaris. It is recognised by its weak trailing culms, few digitate racemes, smooth-edged rhachis and narrow spikelets with contiguous lateral nerves; also the upper glume is often shorter than that of Digitaria ciliaris.

Annual. Culms slender, trailing, branching, 30–50 cm tall, glabrous. Leaf sheaths usually glabrous; leaf blades linear-lanceolate, 2–6 × 0.3–0.7 cm, abaxial surface scabrous, adaxial surface glabrous, pubescent or papillose-pilose at base; ligule 0.75–2 mm. Inflorescence digitate; racemes 2–3(–4), slender, 4–10 cm; spikelets paired, loosely imbricate by about half their length; rachis triquetrous, narrowly winged, ca. 0.6 mm broad, margins smooth or almost so. Spikelets narrowly lanceolate, 2.8–3 mm; lower glume triangular, 0.2–0.3 mm; upper glume narrow, long triangular, 1/3–2/3 as long as spikelet, 1–3-veined, villous throughout; lower lemma as long as spikelet, 5–7-veined, a broad intervein space on either side of midvein, lateral veins very close together near margin, appressed silky pubescent, very rarely with a ciliate fringe, never setose; upper lemma yellowish at maturity, narrowly lanceolate. Anthers 0.5–1 mm. Fl. and fr. summer–autumn. 2n = 18.

Trailing annual; culms 20-40 cm long, very slender. Leaf-blades narrowly lanceolate, 2-7 cm long, 2-5 mm wide. Inflorescence digitate with 2-4 racemes; racemes 3-9 cm long, the spikelets binate and loosely overlapping by about half their length on a narrowly winged triquetrous rhachis with almost smooth edges. Spikelets narrowly lanceolate, 2.5-3 mm long; lower glume an inconspicuous ovate scale up to 0.3 mm long; upper glume one-third to two-thirds as long as the spikelet, 3-nerved; lower lemma as long as the spikelet, 5(-7)-nerved, with a wide central interspace and the lateral nerves so close together that the lemma is apparently 3-nerved, appressed or silky pubescent, very rarely with a ciliate fringe, never with bristles; fruit narrowly lanceolate, yellowish or pale brown.

Himalaya, S.E. Asia, Polynesia.

Distribution: Pakistan (Punjab, introduced); Tanzania, Mauritius and the Seychelles, through tropical Asia to the Pacific Islands; introduced in a few other places.

700-1400 m

Fl. & Fr. Per.: October.

Moist grasslands, roadsides, weedy places. Anhui, Fujian, Guangdong, Guangxi, Hainan, Jiangxi, Taiwan, Yunnan, Zhejiang [India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Philippines, Thailand; Australia, Indian Ocean Islands, Madagascar, Pacific Islands; introduced in Pakistan, Tanzania, and a few other places].

Panicum radicosum J. Presl, Reliq. Haenk. 1: 297. 1830.

Panicum radicosum J. Presl, Reliq. Haenk. 1: 297. 1830; Digitaria chinensis Hornemann var. hirsuta (Honda) Ohwi; D. formosana Rendle; D. formosana var. hirsuta (Honda) Henrard; D. radicosa var. hirsuta (Honda) C. C. Hsu; D. tenuispica Rendle; D. timorensis (Kunth) Balansa; Panicum formosanum (Rendle) Makino & Nemoto; P. timorense Kunth; Syntherisma formosana (Rendle) Honda; S. formosana var. hirsuta Honda.

Annuals, Terrestrial, not aquatic, Rhizomes present, Stolons or runners present, Stems trailing, spreading or prostrate, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems mat or turf forming, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, 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, Leaf blades more or less hairy, Ligule present, Ligule an unf ringed 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 paired at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating below the glumes, Spikelets secund, in rows on one side 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 equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Glume surface hairy, villous or pilose, Glumes 3 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.