36. Cyperus esculentus Linnaeus var. sativus Boeckeler, Linnaea. 36: 290. 1870.
油莎草 you suo cao
Perennials. Root fibrous. Stolons several, apex swollen into a tuber; tubers ellipsoid to globose, 10-18 × 5-8 mm, conspicuously nodose, gray tomentose when old. Culms solitary, 10-40 cm tall, triquetrous, smooth, with several leaves at basal part. Leaves ± congested, longer to shorter than culm; sheath reddish brown; leaf blade yellowish green to light green, 3-6 mm wide, margin flat or revolute. Involucral bracts 3-6, basal 2 longer than inflorescence. Inflorescence a simple or compound anthela; rays 5-10, to 12 cm, base sometimes ramose. Spikes ovoid, with 5-14 laxly arranged spikelets. Spikelets distichous, linear to oblong, 1-1.5 cm × 1.6-1.8(-2) mm, subcompressed, divaricate after anthesis, 10-20-flowered; rachilla broadly winged. Glumes yellowish to golden or pale brown, ± laxly imbricate, extended at maturity, ovate to ovate-elliptic, 2.2-2.6 mm, 7-veined, margin apically white hyaline, apex truncate and mucronate. Stamens 3; anthers linear; connective prominent beyond anthers into small ovoid appendage. Style long; stigmas 3, ± long. Nutlet brownish gray, ellipsoid, ca. 1/2 as long as subtending glume, 3-sided, shiny, densely puncticulate.
Cultivated in Guangxi, Heilongjiang, Liaoning, Xinjiang, and Yunnan; collected as a naturalized plant in Shandong, Taiwan, and perhaps elsewhere [native to Mediterranean region].
Cyperus esculentus var. esculentus occurs in the Mediterranean region and differs by having globose to ovoid tubers, anthela rays to 4 cm, and ellipsoid nutlets. Cyperus esculentus var. sativus was introduced to China before the 1970s and is now grown as an oil plant. The oil is used as an edible or industrial oil. The tubers could be used as a starch source. This herb grows and reproduces quickly and is good for soil conservation.