This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Scirpus validus Vahl, Enum. 2: 268. 1806.
Perennial by stout rootstocks, culm stout, terete, smooth, erect, 3°-9° tall, sometimes nearly 1' in diameter, sheathed below, the upper sheath occasionally extended into a short leaf. Involucral leaf solitary, erect, shorter than the umbel, appearing as if continuing the culm; umbel compound, appearing lateral, its primary rays slender, spreading, 1/2'-2 1/2' long, bracts linear-lanceolate, pubescent; spikelets oblong-conic, sessile or some of them peduncled, in capitate clusters of 1-5, obtuse or acute, 2 1/2"-6" long, 1 1/2"-2" in diameter; scales ovate to suborbicular, slightly pubescent, with a rather strong midvein which is sometimes excurrent into a short tip; bristles 4-6, downwardly barbed, equalling or longer than the achene; stamens 3; style 2-cleft; achene planoconvex, obovate, nearly as long as the scale, gray to brown, abruptly mucronate, a little more than 1 1/2' wide.
In ponds and swamps, throughout North America, except the extreme north, and in the West Indies. The Old World S. lacust ris L., with which our plant has been confused, has a 3-cleft style. Black-rush. Bolder or Boulder Bast. Tule. June-Sept.
S. lacustris occidentalis S. Wats. Bot. Cal. 2: 218.
1880. S". occidentalis Chase, Rhodora 6: 68. 1904.
Similar to S". validus, tall, the culms firmer in texture, the margins of the basal sheaths becoming fibrillose. Involucral leaf shorter than the compound umbel; primary rays rather stiff; bracts viscid at the tip; spikelets clustered in 2's to 7's, or solitary, oblong-cylindric, 10" long or less, about 2" thick, acute or blunt-ish; scales ovate, short-awned, viscid above; style 2-cleft; achene biconvex, obovate, dull, nearly 1" wide, much shorter than the scale.
Borders of lakes and streams, Newfoundland to British Columbia, New York, Missouri, Utah and California. July-Sept.
S". heterochaetus Chase, Rhodora 6: 70. 1904.
Perennial by rather stout rootstocks; culms slender, sheathed below, 6° high or less. Involucral leaf much shorter than the compound umbel; primary rays slender, 4' long or less; bracts acuminate, glabrous; spikelets solitary, ovoid to ellipsoid, acutish, 4"-7" long, about 2 1/2" thick; scales ovate, glabrous, often erose-margined; style 3-cleft; bristles 2-4, unequal, as long as or shorter than the achene; achene about 1" wide, obovate, yellowish, shorter than the scale.
Scirpus californicus (C. A. Meyer) Britton, of the western and southern states and tropical continental America, admitted in the first edition of this work, has not been definitely established as growing within our limits. It has plumose bristles.