Streambank Bulrush

In North America Schoenoplectus triqueter is known only from the tidal Columbia River system (B. W. Lightcap and A. E. Schuyler 1984), where it forms fertile hybrids with S. tabernaemontani [S. ×kuekenthalianus (Junge) D. H. Kent = Scirpus ×scheuchzeri Brugg]. Fertile hybrids between the same species also occur in Europe.

Rhizomes 1.5–5 mm diam. Culms sharply trigonous, 0.5–1.5 m × 2–4 mm. Leaves 3–4, basal, smooth; sheath fronts not pinnate-fibrillose; blades 1 or 2, thickly V-shaped in cross section, to equaling sheath length. Inflorescences 1–2 timesbranched or subcapitate or of 1 spikelet, branches to 4 cm; proximal bract usually erect, trigonous, 2–7 cm. Spikelets 1–35, in clusters or solitary, 5–12 × 3–4 mm; scales straw-colored to orange-brown or midrib greenish, usually clearly lineolate-spotted, ovate, 3–3.5 × 2.5 mm, flanks ribless, midrib proximally spinulose, apex acute to rounded, notch 0.3 mm deep, awn 0.3 mm, sparsely spinulose. Flowers: perianth members 4–6, brown, bristlelike, equaling to less than 1/2 of achene body, retrorsely spinulose; anthers 2 mm; crest short, spinulose; styles 2-fid. Achenes brown, biconvex, ovoid to obovoid, 2–2.5 × 1.5–2 mm; beak 0.1–0.2 mm. 2n = 42.

Perennial, 50-125 cm. Rhizome creeping or stoloniferous, 2-4 mm diam., brown or reddish brown. Stem 2-6(-10) mm diam., distal parts sharply, proximal parts obtusely trigonous, smooth, glaucous green. Sheaths 3, ephemeral, green or often with reddish tint, mouth deeply oblique, margins widely scarious; blades mostly reduced to mucro, uppermost up to 50 mm, channelled, smooth, apex obtusely pointed. Inflorescence of (1-)3-7 sessile spikes, 15-25 mm diam., or a multiple spike; lowest bract to c. 35 mm, trigonous, smooth; primary branches 0-7, up to 30 mm, each with (1-)2-4 sessile spikes; secondary branches occasional, up to 8 mm. Spikes 8-12 x 4-7 mm, ovoid; glumes rather loosely imbricate, 3-4.1 mm, cymbiform, mid-nerve mostly smooth, mucro barbed, up to 0.8 mm, sides inconspicuously nerved, brown or yellowish brown, smooth, apex rounded, often truncate, margins scarious, ciliate. Perianth bristles 4-6, about equalling nut; stamens 3, anthers 1.5-2 mm; stigmas 2. Nut 2.2-3.2 x 1.3-2 mm, ellipsoid or ovoid, bi-convex or almost plano-convex, smooth, yellow brown, glossy.

introduced; Oreg., Wash.; Eurasia.

Distribution: Europe to Japan, China and Taiwan, from Caucasus to Tadjikistan, Pakistan and N. India; Egypt, S. Africa.

Fl. Per.: May - July.

Fruiting summer.

Freshwater tidal shores, marshes, dredge spoil; 0m.

Alluvial meadows, by rivers and lakes, rice fields.

Scirpus triqueter Linnaeus, Mant. Pl. 1: 29. 1767

Scirpus triqueter L., Mant. Pl. 1: 29. 1767; C. B. Clarke, l.c. 658; R. R. Stewart, l.c. 104.