Southern Crabgrass

Digitaria ciliaris is a pantropical, weedy annual very variable in spikelet pubescence and nervation. It lies at the center of a complex of similar and somewhat intergrading, weedy species including D. bi-cornis, D. cruciata, D. henryi, D. radicosa, D. sanguinalis, and D. seti-gera. Occasionally intermediate specimens will be encountered that are difficult to place.

Most species in this complex include forms with or without stiff, glassy bristles near the margins of the lower lemma. These lie flat along the lemma when young, coloring yellow and spreading as a conspicuous pectinate fringe at maturity. The pectinate form of Digitaria ciliaris is sometimes distinguished at varietal rank.

Paspalum sanguinale (Linn.) Lam. var. rottleri Hook.f. is typified by two sheets, Wight 3032 and Wight 3033, both at Kew. Of these, the former is Digitaria ciliaris and the latter Digitaria bicornis (Lam.) Loud. In the protologue to the variety, Hooker described the wings of the rhachis as being “two or three times broader than the midrib.” Since this character does not agree with Digitaria bicornis (including Wight 3033), the specimen Wight 3032 is selected as the lectotype of var. rottleri. This is included in the synomymy of Digitaria ciliaris because the spikelets are narrow and apparently lack the spiny protuberences on the nerves of the lemma.

Digitaria ciliaris is a polymorphic species showing at least four parallel series based on quite independent sources of variation. The rhachis may have long white hairs (rhachiseta) or not; in terms of indumentum the spikelets of a pair may be the same or different (biformis); the spikelets (independently in each pair) may be glabrous (nubica), long or short hairy (ciliaris, desvauxii) or conspicuously fringed (criniformis, fimbriata); one or both spikelets may be beset with stiff glassy bristles (chrysoblephara, willdenowii). None of these variants shows any indication of geographical segration, and since there are at least these four independent sources of variation the number of potential varieties is enormous, but none would be of any taxonomic significance. The sporadic occurence of the siliceous spines characteristic of Digitaria sanguinalis in spikelets otherwise typical of Digitaria ciliaris suggests that there may be some gene-flow between these two species in Pakistan.

Digitaria bicornis (Lam.) Loud. is often included in subsp. chrysoblephara (or vice versa, see Veldkamp 1973) by virtue of its possession of glassy bristles, but like Digitaria ciliaris it too shows several types of indumentum and quite frequently is perfectly glabrous (even to the exclusion of the glassy bristles). It is in fact a distinct species differing in a number of important characters. There are normally only 2, sometimes 3 racemes each with a slightly swollen base. The midrib is thick and the wings are usually extremely narrow. The pedicels are stout and straight and this, combined with the thick midrib, gives the spikelets the appearance of being sunk in the rhachis. The lower lemma is horny with much thickened, contiguous or closely spaced nerves. The first pair of interspaces, and the second where present, are reduced to deep V-shaped grooves. The lemma characters are best seen in the subsessile spikelets towards the base of the raceme. True Digitaria bicornis does not occur in Pakistan, being confined to the warmer parts of southern India, Sri Lanka and Burma.

Digitaria ciliaris is a widespread tropical weed.

Annuals; culm weak, base decumbent, branching, 50-100 cm tall. Blade linear, 8-20 cm long, 50-12 mm wide; sheath more or less pilose; ligule membranaceous, 1-3 mm long, truncate. Inflorescence in subcontracted 3-8 digitate racemes, recemes 5-15 cm long; rachis 0.6-1 mm wide, margins serrate. Spikelets suppressed on one side of rachis, ca. 3 mm long, greenish or purplish; pedicels unequal, triangular, serrate; lower glume minute but distinct, ca. 2 mm long, triangular; upper glume lanceolate, 1/2- 3/5 as long as spikelet, narrow, margins ciliate, 3-veined; lower lemma broadly lanceolate, strongly 5-7 veined, membranaceous, lateral intervein spaces appressedly pubescent, hairs sometimes spreading at maturity but connected at apex; upper lemma lanceolate, coriaceous, pale green to yellowish brown, as long as lower lemma; anther ca. 0.9 mm long.

Annual. Culms decumbent at base, branching and rooting at lower nodes, 30–100 cm tall. Leaf sheaths ± pilose; leaf blades linear to linear-lanceolate, 5–20 × 0.3–1 cm, adaxial surface usually pilose, margins thickened and scabrous; ligule 1–2 mm. Inflorescence digitate or subdigitate, axis short; racemes 3–10, 5–17 cm; spikelets paired, imbricate by about 2/3 their length; rachis winged, ca. 1 mm broad, midrib triquetrous, margins scabrous. Spikelets lanceolate, 2.5–3.5 mm, acute; lower glume very small, triangular; upper glume lanceolate, 2/3–4/5 as long as spikelet, 3-veined, pilose; lower lemma as long as spikelet, 7-veined, veins evenly spaced or a broader glabrous interspace flanking the midvein, lateral interveins appressed pubescent to ciliate or villous, sometimes with a halo-like fringe, sometimes setose; upper lemma yellowish green, gray or pale brown, elliptic, as long as lower lemma, apex acuminate. Fl. and fr. May–Oct. 2n = 36, 54, 72.

Annuals; cume tufted, 30-50 cm high. Blade linear-lanceolate, 4-8 cm long, 3-6 mm wide, villous; sheath short, loose, hirsute; ligule dry and membranaceous, obtuse, ca. 2 mm long, glabrous. Inflorescence in digitate racemes, racemes 2-5. Spikelets ovoid-lanceolate, acute, 3-4 mm long, pilose; lower glume minute, reduced into a point of ca. 0.3 mm long, veinless; upper glume obtuse, lanceolate, ca. 2.7 mm long, 3-veined, long pilose; lower lemma acute, lanceolate, ca. 3 mm long, 5-7-viened, pilose; upper lemma slightly shorter than lower lemma, acuminate, slightly coriaceous, margins incolute, glabrous; anther ca. 1.3 mm long.

Annual; culms 20-100 cm high, decumbent at the base and geniculately ascending. Leaf-blades broadly linear, 3-25 cm long, 3-10 mm wide. Inflorescence digitate or subdigitate (axis up to 5 cm long in robust specimens), composed of 2-12 racemes; racemes stiff, 6-22 cm long, sometimes adorned with sparse long white hairs, the spikelets binate and overlapping by about two-thirds their length on a winged rhachis with triquetrous midrib; pedicels triquetrous, scabrid, obtuse or slightly expanded at the tip. Spikelets narrowly elliptic, (2-)2.5-3.3 (-3.7) mm long, sharply acute; lower glume distinct, 0.2-0.4 mm long and triangular; upper glume at least half as long as the spikelet, typically two-thirds to three-quarters as long, 3-nerved; lower lemma as long as the spikelet, 7-nerved, the nerves smooth and evenly spaced or with a wide interspace flanking the midrib (sometimes those of the subsessile spikelet even and of the pedicelled spikelet spaced), appressed puberulous, silky pubescent or rarely shortly villous, often encompassed by a ciliate frill, occasionally glabrous, one or both spikelets often beset with stiff glassy bristles; fruit ellipsoid, grey to light brown.

Tropics of Old World.

The tropical and warm temperate regions of the world. Taiwan, in wayside and open ground, also cultivated as a fodder grass.

Endemic to Taiwan, in sandy littoral areas.

Distribution: Pakistan (Sind, Punjab, N.W.F.P. & Kashmir); common throughout much of the tropics.

600-1500 m

Fl. & Fr. Per.: July-October.

Roadsides, weedy places. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [throughout the tropics and subtropics, but rare in Africa].

Panicum ciliare Retz., Observ. Bot. 4: 16. 1786.

Syntherisma sericea Honda, Bot. Mag. (Tokyo) 38: 127. 1924.

Annuals, Terrestrial, not aquatic, Rhizomes present, Stems nodes swollen or brittle, 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, 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, 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 digitat ely 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.

At Peradeniya Royal Botanical Garden.

Digitaria ciliaris is a species of grass known by the common names southern crabgrass, tropical finger-grass, tropical crabgrass or summer grass.

The grass is known as "ගුරු තණ - guru thana" in Sri Lanka.