Swaying Bulrush

Schoenoplectus subterminalis often forms lawnlike, underwater mats that are entirely vegetative or have only the inflorescences emergent. This species is probably extirpated from Illinois. Schoenoplectus subterminalis var. terrestris Paine [= S. subterminalis forma terrestris (Paine) Fernald] probably does not deserve taxonomic recognition.

Plants mat-forming; rhizomes to 1 mm diam; terminal tubers sometimes present, to 3 mm thick, fleshy. Culms subcylindric, 0.2–1.5 m × 0.5–1 mm. Leaves 3–20+, smooth; sheath fronts sometimes delicately pinnate-fibrillose; blades 3–20, when erect C-shaped in cross section proximally, elliptic most of length, when submerged usually flaccid and filiform to narrowly ribbonlike, probably longer than sheath, 0.2–1 mm wide. Inflorescences a solitary, erect spikelet; proximal bract erect, like stiff leaf blade, 7–60 mm. Spikelets 5–15 × 3–7 mm; scales pale brown, or central region green when young, ovate-lanceolate, 4–6 × 1.5 mm, smooth, margins sometimes ciliolate apically at 40X, midrib obscure, apex acute, entire, minutely mucronate. Flowers: perianth members 6, brown, bristlelike, from 1/2 of to equaling achene beak, spinulose; anthers 2–3.5 mm; styles 3-fid. Achenes brown, strongly trigonous, obovoid to obpyriform, (2.5–)3–3.5 × 1.5–1.7 mm; beak 0.3–0.8 mm. 2n = 72.

B.C., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask.; Ala., Alaska, Calif., Conn., Del., Fla., Ga., Idaho, Ill., Ind., Maine, Md., Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Utah, Vt., Va., Wash., Wis.

Fruiting summer.

Submerged to emergent in water to 1 m or sometimes terrestrial, fresh lakes, streams, bogs; 10–2200m.

Scirpus subterminalis Torrey, Fl. N. Middle United States 1: 47. 1824

Scirpus subterminalis Torr. Fl. U. S. 47. 1823
Scirpus subterminalis var. terrestris Paine, Ann. Rep. N. Y. State Cab. 18: 148. 1865. Scirpus subterminalis f. terrestris Fernald, Rhodora 45: 288. 1943.
Aquatic perennial; rhizome slender, 1 mm. thick, often reddish; culms 2-6 dm. long, 0.6-1 mm. broad, slender, flaccid, terete, nodulose; sheaths green or white below, the blades many, very slender, channeled, 2-6 dm. long; involucral bract single, erect, 1-7 mm. long; spikelet solitary, ovoid to oblong-cylindric, 4-18 mm. long, 3-5 mm. broad; scales 5 mm. long, strawbrown with a broad, green midrib, ovate-lanceolate, acute; bristles 6, straw-brown, retrorsely barbed, about equaling the achene; style trifid; anthers 3 mm. long; achene 2.5 mm. long, 1.5 mm. broad, brown, smooth, obovoid, trigonous, beaked.
Type locality: Near Deerfield, Massachusetts.
Distribution: Uncommon, in bogs, swamps, and slow streams; Newfoundland, south to South Carolina, westward to British Columbia and Oregon; Mississippi; Alaska.

Schoenoplectus subterminalis is a species of flowering plant in the sedge family known by the common names water bulrush, water club-rush, and swaying bulrush. It is native to North America, where it is known from many parts of the Canada and the United States. It has been common in the northeastern US and eastern Canada as well as the Great Lakes region, as well as many locations in the mountains of the West, though apparently absent from the Southwest and from most of the Great Plains.

Schoenoplectus subterminalis grows in moist and wet habitat, and often grows in shallow water, sometimes entirely submerged. It is a perennial herb forming mats or tufts of very narrow cylindrical stems easily exceeding one meter long. There is a rhizome and sometimes tubers grow on it. When the plant grows in water only the inflorescences and the tips of the leaf blades break the surface. The inflorescence is generally a single cone-shaped spikelet at the end of the stem accompanied by a stiff, stemlike bract.