Cogongrass

This species is extremely polymorphic, but nevertheless easily recognizable by its dense, narrowly cylindrical, silky white inflorescence. The blackish stigmas are persistent and very obvious among the white hairs. The species has been classified into three varieties, which show some geographic separation. Two occur in China and a third is found in Africa. However, there is a great deal of intergradation and also variation within the varieties.

This widespread, noxious weed of disturbed ground and cultivation spreads vigorously by its rhizomes, which are almost impossible to eradicate, and may cover large areas of ground. It flourishes in grasslands that are frequently burned, and the young shoots provide good fodder. It is also used for medicine and fiber.

Sword Grass or Blady Grass (Australia) is a common weed of cultivation and flourishes in grassland which is subject to annual burning, flowering just before the fires begin. The seeds remain enclosed in the glumes and lemmas and, surrounded by the long silky hairs, are carried long distances by strong winds which often. blow at these times. The rhizomes are tenacious of life and new plants will regenerate from even a small fragment, making the grass extremely difficult to eradicate. The plant itself is excellent for thatching, can be made into paper, and is also relished by grazing animals after the annual fires when the young shoots appear. It is seldom eaten when old.

Three varieties of Imperata cylindrical are commonly recognised:

var. cylindrica. Leaf-blades rolled. Mediterranean and Middle East.

var. africana. Leaf-blades flat; spikelets 3-5.7 mm long (mean 4.5). Africa.

var. major. Leaf-blades flat; spikelets 2.5-43 mm long (mean 33). Tropical Asia and Australasia; also possibly parts of tropical East Africa.

Although the differences can be demonstrated statistically the varieties inter-grade so much that individual specimens are often unidentifiable; the hairiness of the node, on which reliance has sometimes been placed, is extremely unreliable as a means of identification. It seems best to ignore the varietal classification with the understanding that there is a number of imperfectly separable geographical variants. Pakistani material appears to be assignable to var. major although specimens grading into var. cylindrical are not uncommon.

Perennial, basal sheaths becoming fibrous; rhizomes widely spreading, tough, scaly. Culms solitary or tufted, 25–120 cm tall, 1.5–3 mm in diam., 1–4-noded, nodes glabrous or bearded. Leaf sheaths glabrous or pilose at margin and mouth; leaf blades flat or rolled, stiffly erect, 20–100 × 0.8–2 cm, culm blades 1–3 cm, adaxial surface puberulous, margins scabrid, base straight or narrowed, apex long acuminate; ligule 1–2 mm. Panicle cylindrical, copiously hairy, 6–20 cm, lowermost branches sometimes loose. Spikelets 2.5–6 mm; callus with 12–16 mm silky hairs; glumes 5–9-veined, back with long silky hairs ca. 3 times glume length, apex slightly obtuse or acuminate; lower lemma ovate-lanceolate, 2/3 length of glumes, ciliate, acute or denticulate; upper lemma ovate, 1/2 length of glumes, denticulate, ciliate, palea equal to lemma. Anthers 2, 2–4 mm. Stigmas purplish black. Fl. and fr. Apr–Aug. 2n = 20.

Agressively rhizomatous perennial, forming tufts of leaves from a scaly rhizome; culms 10-120 cm high, erect. Leaf-blades basal, flat (in Southeast Asia), 3-100 cm or more long, 2-20 mm wide, stiffly erect. Panicle spiciform, cylindrical, sometimes with the lowermost branches loose, 3-22 cm long, obscured in copious silky white hairs. Spikelets 2.2-6 mm long; stamens 2.

Distribution: Pakistan (Sind, Baluchistan, Punjab, N.W.F.P., Gilgit & Kashmir); throughout the Old World tropics, extending to the Mediterranean and the Middle East; also in Chile.

Fl. & Fr. Per.: April-June.

River and seashore sands, disturbed grassy places, cultivations. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Nei Mongol, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, India, Indonesia, Japan, Kazakhstan, Korea, Kyrgyzstan, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, Philippines, Russia, Sri Lanka, Thailand, Turkmenistan, Uzbekistan, Vietnam; Africa, SW Asia, Australia, S Europe].