14. Cyperus iria L.

Pl. 68 d–f; Map 258

Plants annual, tufted, lacking rhizomes and tubers. Aerial stems 15–60 cm long, sharply trigonous, smooth. Leaf blades 10–40 cm long, 3–7 mm wide, shorter than to about as long as the stems. Inflorescences irregularly compound umbels often with usually 1 sessile panicle and usually with 3–8 primary rays, each ray smooth, with a panicle at the tip, the panicle branches ending in open, irregular spikes. Inflorescence bracts 4–7, mostly longer than the rays, mostly ascending. Spikes 10–20 mm long, with 10–30 spikelets, irregular in outline, open, the spikelets mostly ascending, attached distantly and more or less alternately on the axis, the spikelet bases readily visible. Spikelets 5–20 mm long, linear to narrowly elliptic, rounded at the tip, somewhat flattened in cross-section, with 8–22 florets, the fruits and scales shed successively from the base to the tip, leaving the persistent axis. Spikelet axis not winged. Spikelet scales 1.2–1.7 mm long, not or slightly overlapping, appressed or ascending, broadly obovate, rounded to bluntly angled along the back, rounded or shallowly notched at the tip, the midrib sometimes extended into a minute point, straight, with 5 nerves, yellowish brown, the margins sometimes somewhat lighter, the midrib green. Stamens 2(3), the anthers 0.3–0.4 mm long. Stigmas 3. Fruits 1.0–1.5 mm long, obovate in outline, 3-angled in cross-section, the sides slightly concave, the surface finely pebbled, brown to black or nearly so at maturity, shiny. 2n=16, 72, 128. July–October.

Introduced, scattered in the Mississippi Lowlands (native of Europe, Asia, introduced in the southeastern U.S. west to Missouri and Texas, and also from Mexico to South America). A weed in crop fields; also roadsides, fallow fields, and open, sandy areas.

Steyermark (1963) knew this species only from two collections made during the 1950s. Since that time it has become much more common in portions of the Bootheel.