Paspalum distichum L.

The length of the lower glume is very variable, even within a single raceme. The spikelets are not obviously hairy because the pubescent upper glume faces inward, but the creeping habit together with paired racemes of plump spikelets are distinctive. Rarely the upper glume is glabrous, but such specimens can be separated from the closely related Paspalum vaginatum by spikelet shape and by the longer, apiculate fertile floret.

Paspalum paspalodes closely resembles the more tropical Paspalum vaginatum Sw. The latter can be recognised by its narrowly ovate-elliptic spikelets, the papery upper glume and lower lemma, and the glabrous upper glume.

The type sheet of Paspalum distichum Linn. bears pieces of two different species. One is Paspalum paspalodes, to which the name “Paspalum distichum” has universally been applied; and Paspalum vaginatum, beside which the faded inscription “Br” indicates that this was the plant collected by Browne. In Sp. Pl., ed. 2, 1:82. 1762, Linnaeus gave the locality of Paspalum distichum as Jamaica, and as Browne collected in Jamaica it appears that the specimen known as Paspalum vaginatum is in fact the true type of Paspalum distichum. The fading of the inscription and the later addition of other material to this sheet are the source of the present nomenclatural confusion. Our species can no longer be called Paspalum distichum, but whether Paspalum vaginatum should be renamed Paspalum distichum is questionable. Clayton (Fl. Trop. E. Afr., Gram. part 3, in press) maintains that to start switching the names of two very similar species at this late stage will cause endless unnecessary confusion. This is a valid point of view resulting in Paspalum distichum Linn. being abandoned altogether as a nomen confusum.

Paspalum paspalodes provides good pasturage, especially on alluvial flats. Known as Knotgrass (in North America) it occurs as a garden weed, along ditches and irrigation channels, as a weed in rice-fields, and is gregarious in swampy places.

Perennials; stolon creeping, stout, flowering culm very short, 20-50 cm tall, nodes thickened and pubescent. Blade 5-10 cm long, 3-7 mm wide, glabrous; sheath glabrous, margins ciliate; ligule membranaceous, truncate and fringed, 2-3 mm long, glabrous abaxially; Racemes 2, 2-6 cm long; rachis 1.5- 2 mm wide, flat. Spikelets solitary, obovate-oblong, acute, loosely pubesent, ca. 3 mm long; lower glume usually absent, developed in a few spikelets, triangular in shape, ca. 0.3 mm long; upper glume appressed pubescent; lower lemma 3-5-veined, usually glabrous, acute; upper lemma nearly as long as spikelet, coriaceous, pale green, acute, hairy at apex.

Perennial with rhizomes and stolons. Culms 20–50 cm tall, nodes usually pubescent. Leaf sheaths keeled, glabrous, margins ciliate; leaf blades linear, 5–10 × 0.3–0.7 cm, glabrous, apex acute; ligule 2–3 mm. Inflorescence of 2(–3) racemes arising together or separated by a short axis; racemes 3–7 cm; spikelets single, in 2 rows; rachis straplike, 1.5–2 mm wide. Spikelets pallid, obovate-oblong, plano-convex, 3–3.5 mm, acute; lower glume vestigial or a narrow triangular scale up to 1/2 spikelet length or more; upper glume papery, 3–5-veined with distinct middle vein, loosely appressed pubescent; lower lemma 3–5-veined, usually glabrous; upper lemma pale green, almost equal to spikelet, cartilaginous, apex apiculate and minutely pubescent. Fl. and fr. May–Sep. 2n = 40, 48, 60.

Creeping stoloniferous perennial; culms 6-50 cm high. Leaf-blades 5-20 cm long, 2.5.6.5 mm wide. Inflorescence composed of 2(4) conjugate racemes, each raceme 1.5-7 cm long, the spikelets single in 2 rows on a flattened rhachis 1-2 mm wide. Spikelets ovate, 2.5-3.5 mm long, plano-convex, relatively plump, pale-green; lower glume often present as a small scale; upper glume appressed-puberulent, herbaceous, with a distinct mid-vein; lower lemma similar but glabrous: upper lemma smooth, pallid at maturity.

Tropics & subtropics of Old World.

The tropics and subtropics of the world. Taiwan, in roadsides, dampy places and along ditches.

Distribution: Pakistan (Sind, Punjab, N.W.F.P. & Kashmir); tropics and sub-tropics throughout the world.

200-2000 m

Fl. & Fr. Per.: April-May and again August-September.

Fields, roadsides, ditches and other disturbed places, mostly on moist fertile soils. Anhui, Fujian, Guangxi, Guizhou, Hainan, Henan, Hong Kong, Hubei, Hunan, Jiangsu, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [tropical and warm-temperate regions of the world].

Digitaria paspalodes Michaux; Paspalum paspalodes (Michaux) Scribner.