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common three-square, common three-square bulrush, western bulrush

Rhizomes

often vertical, 1–6 mm thick.

Culms

sharply trigonous;

sides convex to concave proximally, deeply concave to flat distally, 10–200 cm × 1–6 mm.

Leaf blades

proximally V-shaped, distally trigonous to asymmetrically laterally flattened in cross section;

distal blade (1)2–5 times as long as sheath, 50–750 × 2–9 mm.

Inflorescences

proximal bract usually erect, resembling leaf blade but trigonous proximally; (1)3–20 cm.

Spikes

1–5(10), sessile, 5–23 × 3–5(7) mm; floral scales bright (to very dark) orange-, red-brown, or purplish brown to straw-colored, often with prominent linear dots;

midrib mostly paler; ovate, 3.5–6 × 2–3 mm; smooth or awn sparsely spinulose;

margins deciduously ciliolate;

apex acute (to obtuse); notch (0.3)0.5–1 mm deep; awn mostly irregularly bent, 0.5–1.5(2.5) mm.

Flowers

perianth members 4–8, sometimes fewer; bristle-like; equal or unequal; all equaling achene body to all rudimentary, retrorsely spinulose, brown;

stigmas 2–3.

Achenes

biconvex to compressed bluntly trigonous; (2)2.5–3.5 × 1.3–2.3 mm;

beak 0.1–0.5 mm.

2n

=74, 78.

Schoenoplectus pungens

Distribution
[WildflowerSearch map]
[BONAP county map]
Discussion

Freshwater to brackish marshes, lake shores, and fens, often emergent in shallow water. 0–2000 m. BR, BW, Col, CR, ECas, Est, Lava, Owy, Sisk. CA, ID, NV, WA; north to AK, throughout US and southern Canada, south to Mexico; South America; Australia, Europe, New Zealand. Native.

Schoenoplectus pungens and S. americanus share the oxymoronic and yet oddly descriptive common name “Three-square.” Their culms are triangular with prominent angles and the inflorescences are sessile. Schoenoplectus pungens shows considerable variation and has been divided into controversially delimited varieties. The group needs more research.

Source Flora of Oregon, volume 1, page 251
Barbara Wilson, Richard Brainerd, Nick Otting
Sibling taxa
S. acutus, S. americanus, S. californicus, S. heterochaetus, S. mucronatus, S. saximontanus, S. subterminalis, S. tabernaemontani, S. triqueter
Synonyms Schoenoplectus pungens var. badius, Schoenoplectus pungens var. longispicatus, Scirpus americanus, Scirpus americanus var. monophyllos, Scirpus pungens, Scirpus pungens var. longispicatus
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