6. Schoenoplectus heterochaetus (Chase) Soják (great bulrush, slender bulrush)

Pl. 83 a–c; Map 310

Scirpus heterochaetus Chase

Plants perennial with stout rhizomes. Stems 80–250 cm long, hard and not easily crushed, circular or nearly so in cross-section. Leaves 2–4 near the stem bases, the upper 1–2 with well-developed leaf blades, these 2–15 cm long, flattened to C-shaped in cross-section. Leaf sheaths oblique at the tip, the lower ones chestnut-colored, often split open, the margins of the split transparent and membranous, usually becoming somewhat shredded with age. Inflorescences irregular umbels of usually numerous spikelets, these individually stalked or rarely a few stalked clusters of 2 sessile spikelets present, less commonly more highly branched, the bracts 2–3, the main bract 1–8 cm long, the others reduced and scalelike. Spikelets 6–15 mm long, narrowly ovate to lanceolate in outline, mostly pointed at the tip. Spikelet scales 3.5–4.0 mm long, oblong-ovate, irregularly fringed and notched at the tip, light brown to straw-colored, the reddish purple spots and/or short lines (visible under magnification) often present, but not prominent, the midrib less noticeably extended past the main body of the scale 0.2–0.8 mm, usually straight. Perianth bristles 2–4(–5), unequal, mostly shorter than the fruits, relatively slender, flattened and straight to contorted or arched, retrorsely barbed. Stigmas 3. Fruits 2.4–2.9 mm long, ovate to obovate in outline, the tip with a noticeable, narrow beak, unequally and strongly 3-angled, the surface finely granular, straw-colored, turning dark brown, somewhat shiny. 2n=38. May–September.

Uncommon and widely scattered in Missouri, mostly north of the Missouri River (northern U.S. and adjacent Canada south to Oregon and Kentucky). Emergent aquatics on banks of rivers, margins of ponds and lakes, marshes, and sloughs; wet ground in abandoned borrow pits.

This is the least common of the three “great bulrush” species in Missouri. For a discussion of morphological differences between S. heterochaetus and S. tabernaemontani, see the treatment of the latter species. For a discussion of putative hybrids between S. heterochaetus and S. acutus, see the treatment of that species.