1. Schoenoplectus acutus (Muhl. ex Bigelow) Á. Löve & D. Löve (great bulrush, hardstem bulrush)

Pl. 80 e–g; Map 305

Scirpus acutus Muhl. ex Bigelow

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 often 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, mostly sessile in stalked clusters of 3–7, less commonly all nearly sessile or the inflorescence more highly branched, the bracts 2–3, the main bract 2–10 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–)3.5–4.0 mm long, oblong-ovate, irregularly fringed and notched at the tip, pale grayish brown with prominent reddish purple spots and/or short lines (visible under magnification), the midrib noticeably extended past the main body of the scale 0.5–2.0 mm, mostly bent or contorted. Perianth bristles (4–)6, shorter than to slightly longer than the fruits, relatively slender, flattened and straight to contorted or arched, retrorsely barbed. Stigmas 2, less commonly 3 in a few florets. Fruits 2.2–2.6 mm long, ovate to obovate in outline, the tip with a noticeable, narrow beak, unequally biconvex (one side rounded, the other nearly flat) in cross-section, rarely slightly 3-angled, the surface smooth, straw-colored, turning dark brown, somewhat shiny. 2n=36, 38, 42. May–September.

Scattered in the northern half of the state, mostly in floodplains of major rivers (U.S., except most of the southeastern states; Canada). Emergent aquatic on banks of rivers, margins of ponds and lakes, marshes, and sloughs; wet depressions along roadsides and railroads.

This species is less common and of more limited distribution in Missouri than the closely related S. tabernaemontani. Where the two species occur together, apparently fertile hybrids are formed with relatively soft stems and variable spikelet scales often intermediate between the putative parents. Thus far, such hybrids have been recorded from St. Charles and Saline Counties. A single historical collection documents a putative fertile hybrid between S. acutus and S. heterochaetus (S. ×oblongus (Koyama) Sojak). Because these species do not grow together often in Missouri, there may be limited opportunities to locate new sites for this hybrid, which is relatively common elsewhere in the species’ ranges. The uncommon hybrid between S. heterochaetus and S. tabernaemontani has not been recorded from Missouri yet.

The seeds and rootstocks of S. acutus were used for food by Native Americans. The starchy rhizomes were dried and ground into flour and the young growth was eaten raw or boiled.