17. Cyperus odoratus L.

Pl. 67 c–e; Map 261

Torulinium odoratum (L.) S.S. Hooper

C. engelmannii Steud.

C. odoratus var. engelmannii (Steud.) R.C. Carter, S.D. Jones, & Wipff

C. ferruginescens Boeck.

C. odoratus var. squarrosus (Britton)) R.C. Carter, S.D. Jones, & Wipff

Plants annual, often tufted, lacking rhizomes and tubers (sometimes perennial with short rhizomes farther south). Aerial stems 8–100 cm long, bluntly trigonous, smooth. Leaf blades 5–65 cm long, 2–12 mm wide, shorter than to about as long as the stems. Inflorescences irregularly compound umbels often with 1 or more sessile spikes and usually with 2–10 primary rays, each ray smooth, with a cluster of 1–6 sessile or very short-stalked spikes at the tip. Inflorescence bracts 3–10, mostly longer than the rays, spreading to ascending or arched downward. Spikes 10–35 mm long, with 10–60 (rarely more) spikelets, narrowly oblong-ovate in outline, dense or more open, appearing cylindrical, the spikelets mostly spreading at right angles to the axis, attached alternately, but often immediately adjacent to one another, the spikelet bases visible. Spikelets 10–20 mm long, linear, pointed at the tip, circular to slightly flattened in cross-section, with 4–25 florets, breaking apart at fruiting into units consisting of a fruit enclosed on 1 side by a winged section of the jointed axis and on the other side by the spikelet scale. Spikelet scales 2.0–2.8 mm long, somewhat overlapping (not or only slightly overlapping elsewhere), appressed or ascending, ovate-elliptic, rounded along the back, rounded to bluntly pointed at the tip, straight, with 3–11 fine nerves, straw-colored to brown, reddish brown, or orange, the midrib green. Stamens 3, the anthers 0.3–0.5 mm long. Stigmas 3. Fruits 1–2 mm long, oblong to narrowly obovate, 3-angled in cross-section, the surface finely pebbled, brown, shiny. July–October.

Scattered throughout the state, most commonly in the floodplains of the Big Rivers (nearly worldwide in tropical and warm-temperate regions; in the New World from the U.S. and adjacent Canada south to South America and the Caribbean Islands). Mudlflats and sandbars along rivers and streams; margins of sloughs, ponds, and lakes; also roadsides, railroads, crop fields, and moist, disturbed areas.

Many botanists, including Steyermark (1963), have separated C. odoratus as treated here into several segregate species. Steyermark (1963) treated the common Missouri element under the name C. ferruginescens, which was said to differ from true C. odoratus (which he restricted to a few Bootheel collections) in its shorter fruits and spikelet scales. He also keyed C. engelmannii of adjacent Illinois, which has nonoverlapping spikelet scales. Although plants typical of the C. engelmannii morphotype have yet to be collected in Missouri, plants corresponding to Steyermark’s concept of C. odoratus have been found to occur sporadically nearly throughout the state, usually within populations of C. ferruginescens. A number of specimens of intermediate morphology further confuse separation of these taxa. Tucker (1984, 1994), who studied primarily the Mexican and Central American specimens of this complex, concluded that there are no discrete differences to warrant recognition of these segregates as species. Missouri populations seem to justify his decision to treat the C. odoratus complex as a single variable species.