Cyperus microiria Steud.

The name Cyperus amuricus Maximowicz has been misapplied to C. microiria by some American authors (e.g., M. V. McGivney 1938).

Herbs, annual, cespitose. Culms trigonous, (5–)20–60 cm × (0.2–)0.6–2.4 mm, glabrous. Leaves (1–)3–4, V-shaped, 15–40 cm × 3–6 mm. Inflorescences: spikes 2–5(–8), oblong to ovoid, 2–10 cm × 3–12 mm; rays 4–8, to 11 cm; bracts (4–)5(–7), ascending at 45°, V-shaped, (1.5–)8–30(–50) cm × 1–6 mm; rachilla persistent, wingless (successive floral scales 1.1–1.5 mm apart). Spikelets 10–30, spreading, compressed, linear, 4–20 × 1.5–2.1 mm; floral scales deciduous, (2–)6–26, laterally brown to golden brown, edges clear, medially green, 5-ribbed, outermost ribs more noticeable than others, obovate to nearly orbiculate, 1.3–1.8 × 1.2–1.8 mm, margins emarginate, apex mucronulate, mucro 0.2–0.25 mm. Flowers: stamens 2(–3); anthers (0.2–)0.3–0.4 mm, tips of connectives reddish, less than 0.1 mm; styles less than 0.1 mm; stigmas 0.2–0.4(–0.5) mm. Achenes brown, slightly stipitate, obovoid, 1.2–1.4(–1.5) × 0.5–0.7 mm, apex apiculate, surfaces puncticulate.

introduced; Conn., Ky., Mass., N.J., N.Y., Ohio, Pa.; e Asia.

Fruiting summer.

Disturbed soils; 0–100m.

Cyperus iria Linnaeus var. microiria (Steudel) Franchet & Savatier; C. iria var. parviflorus (Nees) Miquel; C. iria var. rectangularis Kükenthal

Cyperus microiria, commonly known as the Asian flatsedge, is a species of sedge from Asia, occurring between the Himalayas in the west to Japan in the east.

The species was first formally described by the botanist Ernst Gottlieb von Steudel in 1854.