Rough Flatsedge

Description

Cyperus retrofractus (Linnaeus) Torrey in J. Carey, Carices North. U.S. 519. 1847. Rough flatsedge Scirpus retrofractus Linnaeus, Sp. Pl. 1: 50. 1753; Cyperus dipsaciformis Fernald; C. retrofractus var. dipsaciformis (Fernald) K-kenthal; Mariscus retrofractus (Linnaeus) Vahl Herbs, perennial, cespitose. Culms with cormlike bases, sharply trigonous, 25-90 cm, glabrous proximally, minutely scabridulous distally. Leaves V-shaped, 14-40 cm - 3.5-8 mm, (pubescent on adaxial side of midrib). Inflorescences: spikes loose, obtrulloid to obdeltoid (broadest near apex, nearly as long as wide), 20-28(-34) - (12-)15-30 mm; rays 4-13, (1-)4-24 cm (longest ray shorter than bracts), glabrous; bracts 3-12, ascending at 30-45-, flat, 3-25 cm - 3-7 mm; rachilla persistent, wings 0.4-0.6 mm wide, covering 3/4 of mature achene. Spikelets 30-50, proximal one reflexed, distal ones divaricate, linear-lanceoloid, - terete, (6.5-) 8-10(-17) - 0.5-0.7 mm; floral scales persistent, 3-6(-8), appressed, stramineous (suffused with reddish purple), 4-5-ribbed laterally, ovate-lanceolate, (4-)4.4-4.9(-5.4) - 1.3-1.5 mm; terminal scale not spinose, apex straight, excurved mucronate, or cuspidate. Flowers: anthers 0.7-1.2 mm; styles 1.5-2 mm; stigmas 2-2.5 mm. Achenes brown to brownish black, narrowly oblong, (2.2-)2.5-3 - 0.6-0.7 mm, base cuneate, apex obtuse, apiculate, surfaces puncticulate.