Flora of North America species comparison

Calamagrostis rubescens grows at 50-2800 m, usually in open montane pine or aspen forests and parklands, infrequently in sagebrush steppes, chaparral, and meadows. It is primarily a species of interior western North America, although it reaches the Pacific coast in southern California. The distribution extends from central British Columbia and Alberta east to the Cypress Hills of eastern Alberta and the Pasquia and Cub hills of Saskatchewan, south to western California, Nevada, northeastern Utah, and central Colorado. It is considered threatened in Saskatchewan.

Calamagrostis rubescens is similar to C. koelerioides (p. 721). The two have traditionally been distinguished by the presence of hairs on the leaf collars of C. rubescens, and their absence from C. koelerioides; a more reliable differentiation is the shorter lemmas, glumes, and awns of C. rubescens. Calamagrostis rubescens and C. porteri (p. 721) appear to be closely related. They may be part of the general phenomenon of eastern and western vicariants.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Calamagrostis purpurascens grows in alpine tundra, on subalpine slopes, in grasslands, sand dunes, meadows, coniferous and deciduous forests, and disturbed soils, usually on rocky ridgetops and slopes and, infrequently, on valley floors. It prefers well- to moderately-drained, medium- to coarse-textured substrates, including scree and talus, that are often calcareous, at elevations from 15-4000 m. Its range extends from Alaska through Canada to Greenland and Newfoundland, including the islands of the Canadian arctic, and south in the western mountains to California and northern New Mexico. It does not occur near the open coast except in the Aleutian Islands, the Arctic, and the Olympic Peninsula in Washington. In Asia, it ranges from eastern and central arctic Siberia south to the Kamchatka Peninsula and Sakhalin Island.

The hairy adaxial leaf surfaces are a reliable diagnostic characteristic for Calamagrostis purpurascens. Many specimens from Washington and Oregon currently identified as C. purpurascens belong to C. tacomensis (p. 716). In addition to differing in its leaf vestiture, C. purpurascens has shorter awns and panicle branches, and more scabrous glumes, than C. tacomensis. Plants of C. purpurascens that have short awns barely projecting beyond the lemma margins have been mistaken for C. montanensis (p. 724), but that species does not have hairy adaxial leaf surfaces.

Calamagrostis purpurascens var. laricina Louis-Marie supposedly has shorter glumes and awns, with the awns barely exserted, if at all. The variety is not recognized here because the range in variation in these two characters is continuous; plants that match the description of var. laricina are widely distributed throughout the range of the species. Some collections having both short and long awns are on the same sheet.

Calamagrostis lepageana Louis-Marie, collected only from Mont-Commis, Quebec, is here included within C. purpurascens. It differs from the typical form in that the panicle is more open; the branches are sparsely short-scabrous; and the glumes are at the shortest limit for the species, and are smooth or sparsely scabrous only on the keels. Other characteristics, including the densely hairy adaxial leaf surfaces, fit C. purpurascens.

According to Norwegian botanist Reidar Elven (pers. comm.), five specimens at ALA, collected from four sites on the Seward Peninsula in Alaska, are distinct from Calamagrostis purpurascens but are related to it, or are possibly a hybrid between C. purpurascens and C. sesquiflora (p. 714). They differ from typical C. purpurascens in having bristly (versus hairy) upper leaf surfaces, and acuminate, dark purple (versus acute, pale pink or lilac) glumes. They can be called C. purpurascens subsp. arctica (Vasey) Hulten; in eastern Russia this taxon is recognized at the species level as C. arctica Vasey.

(Discussion copyrighted by Flora of North America; reprinted with permission.)