14. Scirpus L. (bulrush)

(Smith and Yatskievych, 1996)

Plants perennial, often with stout rhizomes. Aerial stems few to many per plant, erect to ascending (sometimes lax and sprawling in S. divaricatus), unbranched, circular to bluntly triangular in cross-section, glabrous. Leaves basal and alternate along the stems, the sheath apices mostly truncate to shallowly concave (sometimes convex in the S. atrovirens complex), the ligule usually present, appearing as a short, white, scaly ridge, the leaf blades spreading to ascending, flat, glabrous, the margins finely and sharply toothed. Inflorescences terminal, subtended by (1)2 to several leaflike bracts, mostly highly branched, irregularly compound panicles or umbels, the branch-points mostly with reduced, leaflike bracts, composed of numerous spikelets, these 2.5–10.0 mm long, 2–4 mm in diameter, individually stalked and/or sessile in headlike clusters, the scales glabrous. Florets many per spikelet, several-ranked in an overlapping spiral pattern, perfect. Perianth bristles 5–6 or less commonly fewer or none. Stamens 3, less commonly fewer or none. Styles not expanded at the base during flowering, not forming a tubercle, but frequently persisting on the fruit as a short beak. Stigmas 2–3. Ovaries and fruits naked, without a perigynium (saclike covering). Fruits 0.7–2.0 mm long, 3-angled, somewhat flattened (unequally biconvex) or nearly circular in cross-section. About 30 species, worldwide.

In the broad sense, Scirpus contains some 200–300 species and forms the largest generic complex in the tribe Scirpeae and the third largest in the family Cyperaceae (Tucker, 1987). Species limits and the classification of species groups within the complex have remained controversial, in spite of numerous publications addressing these problems. Smith and Yatskievych (1996) reviewed the problems in the context of Missouri taxa and treated these as a polyphyletic complex of five genera, a system that is followed here. Bruhl’s (1995) recent studies suggest that portions of the group (including Bolboschoenus, Scirpus sensu stricto, and Trichophorum) are allied with Dulichium and Fuirena, whereas other portions (including Isolepis and Schoenoplectus) are more closely related to Eleocharis and Eriophorum. However, Bruhl stressed that much further taxonomic work is necessary to clarify the relationships among some of the species groups in the tribe Scirpeae.

The seeds of Scirpus species provide food for waterfowl, which disperse these bulrushes both in mud on their feet and feathers and as undigested seeds in their droppings.

Tucker (1987) reported Cladium mariscoides (Muhl.) Torr., twig rush, for Missouri without documentation. This widespread species occurs primarily along the eastern Coastal Plain of the United States and Canada, and in the Great Lakes region. It is also known to occur in Minnesota, which may account for the mistaken report for Missouri, based upon a presumed specimen label on which the state may have been abbreviated “Mi” or written illegibly. Cladium has the appearance of a robust Scirpus or Rhynchospora but differs from the former in having only 1 (vs. several) fertile floret per spikelet and from the latter in the lack of a tubercle on the fruits. The closest documented sites for C. mariscoides are in Kentucky and Illinois.