Cyperus difformis L. (1756)

Distribution: Common weed from 35o S to 45o N in tropical and subtropical areas of all continents; from S. Europe to Turkey, Iraq, Caucasus, Uzbekistan, Tadjikistan, Pakistan and India.

100-2700 m

Annual, 25-60 cm. Roots reddish-brown. Stem c. 3 mm diam., sharply trigonous, smooth. Leaves shorter than stem; sheaths to c. 10 cm, green or yellow-brown, sometimes with reddish tint, mouth oblique; ligule c. 1 mm, papery, arch of attachment higher than wide; blades up to 50 cm, 3-5 mm wide, keeled, margins smooth, apex trigonous, scabrous. Inflorescence of 1-7 globose partial inflorescences, nearly sessile or peduncles to 30 mm; partial inflorescences 7-15 mm diam., axis tightly digitately branching and rebranching, with c. 100 or more sessile spikes. Bracts 2-3, lowest two foliose, to 20 cm or more, sheath-less. Spikes 2-5 x c. 1 mm, with 5-20 flowers; glumes c. 0.7 mm, deeply cymbiform, blunt, wider than long, midnerve strong, sides brown or dark brown, margins narrowly scarious; rachis compressed, slightly zigzagging, internodes c. 0.8 mm. Stamens 2. Nut c. 0.5 mm, obovoid, sharply trigonous, papillose, yellowish.

Herbs, annual, cespitose. Culms 1–15, trigonous, 7–30 cm × 1.2–2.5 mm, soft (flattened in pressing), glabrous. Leaves 2–7, flat, (2–)7–22 cm × 2.2–4 mm. Inflorescences: heads dense, 7–17 mm diam.; when rays short, heads sessile or nearly so, then densely irregularly lobate, 12–35 mm diam.; rays 1–5, 2–32 mm; bracts 2–4, longest bract erect or nearly so, appearing as continuation of culm, other bracts horizontal to ascending, 1–22 cm × 0.5–3.5 mm, margins and keel minutely scabridulous. Spikelets 30–120, greenish brown to purplish brown, oblong-ellipsoid, compressed, (2–)3–5(–6) × 0.8–1.2 mm; floral scales (6–)12–20(–30), laterally clear margins, stramineous to deep purple, medially greenish, stramineous, or purplish, laterally ribless, medially 3-ribbed, obovate to orbiculate, 0.6–0.8 × 0.6–0.8 mm, apex mucronulate. Flowers: stamens 1 or 2; anthers ovoid-ellipsoid, 0.1 mm, connective not prolonged; styles 0.1 mm; stigmas 0.1–0.3 mm. Achenes light brown, obovoid-ellipsoid, 0.6–0.8 × 0.3–0.4 mm (as long as subtending scale), base cuneate, apex obtuse, apiculate, surfaces finely reticulate, papillose.