This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Cyperus echinatus, Wood
Native. Perennial. Propagates by seeds and by rootstocks.
Time of bloom: July to September.
Seed-time: August to October.
Range: Virginia to Missouri, southward to Florida and Texas.
Habitat: Dry, sandy soil; cultivated fields, waste places.
This Cyperus seems to prefer dry and mellow soils, and often makes itself troublesome in strawberry and melon patches. It springs from short corm-like rootstocks, the culms ten inches to two feet high, slender, smooth, longer than the leaves, which are pale green, less than a quarter-inch wide, smooth with rough edges; the involucre has five to ten bracts, most of them much longer than the umbel; the latter has six to twelve unequal ascending rays, the heads globose or slightly oblong, usually about a half-inch in diameter; spikelets twenty to forty, pale green or somewhat yellowish, spreading, lance-cylindric or only slightly compressed; scales five to eight, narrowly ovate, thin, appressed, striate, with scarious margins; usually the lowest two and the awl-like one at the point of the spikelet are empty. The three-sided, oblong achene is only about half the length of the scale. (Fig. 37.)
Fig. 37. - Baldwin's Cyperus (Cyperus echinatus). X 1/4.
Prevent seed production. Persistent, thorough, and late cultivation is necessary in order to hinder the development and dispersal of seeds and to destroy the rootstocks. Partly ripened heads should never be plowed under, but should be removed, either to compost heap or bonfire.