Culms bluntly angled, smooth or slightly serrulate on 1 angle distally, 10-30 cm. Inflorescences with pistillate heads 2-4 cm wide; proximal spikes appressed to ascending. Pistillate scales green or gold with distal margins white or pale gold, 0.7-1 mm wide, apex long- or short-tapered with awn to 6-12 mm. Anthers 4-6.5 mm. Perigynia appressed-ascending to ascending, with shallowly erose wing 0.4-0.6 mm wide, base acute; beak ± falcate, 3-5 mm from apex to achene, apex notched 0.4-0.6 mm adaxially. Achenes 4-7 × 1.5-2.5 mm. Fruiting spring-summer. Sandy beaches along seacoasts, sounds, bays, and inlets; 0 m; introduced; Del., Md., N.J., N.Y., N.C., Oreg., R.I., Va.; native e Asia. Before Carex kobomugi was formally recognized it was included in C. macrocephala Willdenow ex Sprengel. Carex kobomugi was collected during the early 1900s from ballast and sand near Portland, Oregon, but recent collections are not known; the habitat there may no longer exist. Clones of C. kobomugi have been registered by the U.S. Soil Conservation Service and the New Jersey Agricultural Experiment Station for long-term stabilization of coastal sand dunes. Its introduced range will likely expand.
Usually dioecious; stems very stout, 1-3 dm; lvs yellow-green, stiff, 3-6 mm wide, rough-margined, surpassing the stems; spikes numerous, sessile, densely aggregated into a head that appears almost as a single spike, the staminate heads oblong-cylindric, 3-4 נ1-2 cm, the pistillate ovoid, 3-6 נ2-4 cm; scales acuminate into a stout, often elongate cusp; perigynia ±erect, dark, lance- ovate to elliptic, thickly planoconvex, spongy-thickened below, 10-14 mm, evidently multinerved, the infolded margins lacerately toothed, the beak smooth, sharply bidentate, nearly as long as the body; achene 4-7 mm, unequally trigonous; stigmas 3. Native of e. Asia, intr. in coastal sands from Mass. to Va.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.