甜根子草 tian gen zi cao

Imperata spontanea (Linnaeus) P. Beauvois; Saccharum spontaneum var. roxburghii Honda.

Perennial, with long rhizomes. Culms 1–4 m tall, 0.4–1 cm in diam., 5–10-noded, often hollow in center, nodes bearded, softly pilose below inflorescence. Leaf sheaths pilose at mouth and margin, sometimes tuberculate-pilose throughout; leaf blades 60–180 × 0.2–0.8 cm, glaucous, glabrous, margins serrate, tapering to midrib at base, apex long attentuate; ligule brown, 2–8 mm. Panicle 20–40 cm, axis silky pilose; racemes 4–17 cm; rachis internodes 1.5–5 mm, pilose with long silky hairs. Spikelets 3–4 mm; callus hairs 3–4 times length of spikelet; lower glume papery and dark brown below middle at maturity, membranous and pallid above, back glabrous, margins ciliate above, apex acuminate; lower lemma ovate-lanceolate, equal to glumes; upper lemma linear or linear-oblong, awnless. Lodicules ciliate. Anthers 3, 1.5–2 mm. Fl. and fr. Jul–Sep. 2n = 40–128.

Mountain slopes, gravelly river beds, low grassy places, forming colonies; below 2000 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, Cambodia, India, Indonesia, Japan, Malaysia, Myanmar, New Guinea, Pakistan, Philippines, Sri Lanka, Thailand, Turkmenistan, Vietnam; Africa, SW Asia, Australia, Pacific Islands].

There are numerous local strains comprising a complex series of chromosome numbers. This species hybridizes readily with cultivated sugarcane (Saccharum officinarum) and is used in sugarcane breeding programs. The name S. spontaneum var. juncifolium Hackel (S. juncifo-lium (Hackel) Janaki-Ammal) has been applied to extreme forms with the leaf blades narrowed to the midrib along their whole length.

This species is a good forage grass and an efficient soil binder.