Rocky Mountain bulrush

Scirpus saximontanus Fernald, Rhodora 3: 251. 1901; S. bergsonii Schuyler; S. supinus Linnaeus var. saximontanus (Fernald) T. Koyama

Plants annual or perennial; rhizomes 1 mm diam. Culms often arching to decumbent, cylindric, ridged when dry, 0.09–0.65 m × 0.5–1.5 mm. Leaves 3–4, 1(–2) cauline; sheath fronts not pinnate-fibrillose; blades 1–2, proximally thickly C-shaped in cross section, distally flat, rudimentary to longer than sheath, 1–200 × 0.2–1 mm, smooth or margins distally spinulose. Inflorescences capitate or of 1 spikelet or with 1 or 2 branches to 15 mm; proximal bract erect, like leaf blades, 5–15 cm. Spikelets 1–20; 6–20 × 3 mm; scales pale orange-brown to colorless, midrib region sometimes greenish, ovate, 2.2–3(–3.5) × 1.5 mm, awn sparsely spinulose, margins ciliolate, midrib keeled distally, apex entire, rounded, awn 0.2–0.5 mm or to 1 mm on proximal scale. Flowers: perianth absent; anthers 0.3–0.5 mm; styles 3-fid. Spikelet achenes blackish brown, nearly equilaterally sharply trigonous, ovoid to obovoid, 1.3–1.8 × 1–1.4 mm, with 10–20 mostly sharp ridges; beak 0.1 mm. Amphicarpic achenes trigonous, 2.2–3 mm including stout, tapered beak 0.3 mm, with many obscure to evident horizontal ridges. 2n = 50.

Fruiting late summer–fall, spring–fall (California, Texas). Damp soils to emergent, freshwater ponds, ditches, often drying, disturbed, and sandy areas; 0–2200 m; B.C.; Calif., Colo., Ill., Kans., Mo., Nebr., Ohio, Okla., S.Dak., Tex., Utah, Wyo.; Mexico (San Luis Potosí, Tamaulipas).

The distribution of Schoenoplectus saximontanus is very scattered (local).