Aquatic and Wetland Vascular Plants of the Northern Great Plains

62. Cyperaceae, the Sedge Family

8. Fuirena Rottb. -- Umbrella-grass

1. Fuirena simplex Vahl

Tufted grasslike annual (in this region) with shallow fibrous roots; culms slender, weak, mostly 2-6 dm long, sharply trigonous above. Leaves grasslike, mostly cauline and extending upward to below the inflorescence; blades soft, flat, 2-5 mm wide, sparingly to moderately pubescent; sheaths glabrous to variously hirsute or hispid, hairy at the collar; ligule membranous with a fringe of short hairs. Inflorescence of 1-3 clusters of 2-several spikelets in a terminal head, rarely of a single spikelet (on diminutive culms), each cluster subtended by 2-3 narrow, spreading or reflexed, foliaceous bracts; spikelets ovoid to oblong-ovoid, 4-11 mm long, appearing bristly due to recurved awns of scales; scales numerous and imbricate, reddish-brown toward the base, blackish or blackish-brown on the margins, the body obovate, 1.5-2 mm long, short-pubescent, strongly 3-nerved in the middle, the 3 nerves excurrent into a subterminal, recurved awn 1.5-5 mm long. Flowers perfect; perianth of 3 stipitate scales alternating with 3 retrorsely barbellate bristles, perianth scales oblong-ovate, 3-nerved, mucronate, persistent to, surpassing and enclosing the achene; stamens 3; styles trifid. Achenes light green, sharply trigonous with flat to concave faces, 0.7-1 mm long including the short stipitate base and slender style beak. Aug--Sep. Stream and pond margins and low areas on floodplains, often where sandy; occasional, c and e NE; (IL to MO and NE, s to TX and NM; also Mex., C.Amer. and the Caribbean).

Plants of the northern plains belong to var. aristulata (Torr.) Kral, distinguished from the more southern var. simplex by its annual habit and 3-nerved (rather than 5- to 7-nerved) spikelet scales.

Reference:

Kral, R.  1978.  A synopsis of Fuirena (Cyperaceae) for the Americas
     north of South America.  Sida 7:309-354.

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