7. Pennisetum flaccidum Grisebach, Gött. Nachr. 1868: 86. 1868.
白草 bai cao
Pennisetum centrasiaticum Tzvelev; P. centrasiaticum var. lanpingense S. L. Chen & Y. X. Jin; P. centrasiaticum var. qinghaiense Y. H. Wu; P. flaccidum var. interruptum Grisebach; P. longissimum S. L. Chen & Y. X. Jin var. axiglabrum B. S. Sun & X. Yang; P. mongolicum Franchet; P. sichuanense S. L. Chen & Y. X. Jin var. equidistans B. S. Sun & X. Yang; P. sinense Mez.
Perennial with tough spreading rhizomes. Culms tufted, up to 1 m tall. Leaf sheaths loose, subglabrous, rounded, imbricate at base; leaf blades linear with a broad white midrib, 3–25 × 0.2–1.2 cm, glabrous, acuminate; ligule 1–2 mm. Inflorescences terminal and also sometimes axillary from upper leaf sheaths, linear, straight or slightly flexuous, loose to moderately dense, 5–18 cm; axis glabrous, smooth or scaberulous, beset with short peduncle stumps or scars; involucres enclosing 1 spikelet (rarely 2); bristles many, usually pale green, occasionally purple-tinged, soft, slender, longest 0.9–2 cm, rarely inner thinly plumose. Spikelet narrowly ovate-oblong, 4–7 mm; lower glume usually 1/4 spikelet length or less, obtuse, acute or erose; upper glume 1/3–3/4 spikelet length, 1–3-veined, acuminate; lower floret staminate, lemma as long as spikelet, 3–5(–7)-veined, concave along midline, acuminate-rostrate, palea fully developed; upper lemma acuminate-rostrate, 5-veined; anthers without hairs at tip. Fl. and fr. Jul–Oct.
Hillsides, field margins, roadsides on dry sandy soils, sometimes also on slightly saline alluvial soils on flood plains; 800–5000 m. Gansu, Hebei, Heilongjiang, Henan, Hubei, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Afghanistan, Bhutan, NW India, Kashmir, Nepal, Pakistan, Tajikistan; SW Asia (Iran)].
This is a widespread and rather variable species, but it always has tough, spreading rhizomes, a glabrous inflorescence axis, and involucres of soft bristles. The bristles are usually glabrous, but occasionally a few hairs are present on some of the inner bristles. Specimens with axillary inflorescences (the basis of Pennisetum centrasiaticum var. qinghaiense) occur throughout the range of the species and do not merit separate status.
This species is a good forage grass.