Publication: Taxon. 13: 202. 1964.
selected vouchers: WTU
Notes: FNA23: "Subspecies of Carex scirpoidea grow in a variety of habitats in northern North America. Taxa previously recognized as varieties or separate species are treated here as subspecies of C. scirpoidea. Within the C. scirpoidea complex, all subspecies have the same chromosome number, possess similar achene micromorphology and leaf anatomy, interbreed in greenhouse experiments, and have morphologic characteristics that mostly fall within the normal range for C. scirpoidea.
Carex scirpoidea subsp. stenochlaena is distinguished by lanceolate perigynia that are longer than 3 mm, tapering gradually to a beak, and over 2.5 times as long as wide. The pistillate spikes are clavate, loosely flowered at the base and borne on slender, lax culms (the spikes droop). The pistillate scales are longer than 3 mm and subtend hirsute perigynia.
Specimens of Carex scirpoidea subsp. stenochlaena from the Bitterroot Range in Ravalli County, Montana, best characterize the subspecies. Some specimens from Washington and northern British Columbia exhibit tendencies towards C. scirpoidea subsp. scirpoidea, in which perigynia are just 2.5 times as long as wide and spikes are less clavate, more loosely flowered.
Carex scirpoidea subsp. stenochlaena from British Columbia and Yukon have a tendency to intergrade with subsp. scirpoidea."