Flora of North America species comparison

Elymus curvatus grows in moist or damp soils of open forests, thickets, grasslands, ditches, and disturbed ground, especially on bottomland. It is widespread from British Columbia and Washington, through the Intermountain region and northern Rockies, to the northern Great Plains. It is infrequent or rare in the midwest, the Great Lakes region, and the northeast, and is virtually unknown in the southeast. It is similar to E. virginicus (p. 298), and has sometimes been included in that species as E. virginicus var. submuticus Hook., but is more distinct than the varieties of E. virginicus treated above. Although E. virginicus and E. curvatus overlap greatly in range, E. curvatus usually has a distinct growth form, and its anthesis is 1-2 weeks later (Brooks 1974). Its spikes range from being completely exserted, especially west of the Great Plains, to largely sheathed, especially east of the Mississippi River and in more stressed environments. This geographic trend parallels that within E. virginicus, but sheathed plants of E. curvatus can usually be distinguished by their short awns. Clear transitions to E. virginicus, usually var. jejunus, are rare, but, especially from Missouri to Wisconsin, there are occasional plants with 5-10 mm awns on a few lemmas, especially at the spike tips. Rarely, plants from Missouri and Iowa to Quebec have hispid to hirsute spikelets, suggesting introgression with E. virginicus var. intermedius. There are a few records of apparent hybrids with other species.

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

Elymus glaucus grows in moist to dry soil in meadows, thickets, and open woods. It is widespread in western North America, from Alaska to Saskatchewan, and south to Baja California and New Mexico. It is also sporadic, sometimes appearing transitional to E. trachycaulus (p. 321), from the northern Great Plains to southern Ontario and New York and, as a disjunct, on rocky sites in the Ozark and Ouachita mountains.

Populations can differ greatly in morphology, especially in rhizome development, leaf width, pubescence, and the prevalence of solitary spikelets; their crossing relationships are partly correlated with such variation (Snyder 1950, 1951; Stebbins 1957, Wilson et al. 2001). Rhizome development and the production of solitary spikelets may also be environmental responses. Rhizomatous plants are more common on unstable slopes or sandy soils. Plants with solitary spikelets are more common on poor soil or in shade. They are often confused, particularly in the herbarium, with E. stebbinsii (p. 329) or E. trachycaulus. They differ from E. stebbinsii in their shorter anthers and awned glumes. Distinction from E. trachycaulus can be difficult with herbarium specimens, but is generally easy in the field, E. glaucus having more evenly leafy culms, laxer and wider blades, more tapered glumes that are almost always awned, and shorter anthers than the sympatric E. trachycaulus.

There are reports of natural hybrids with several other species of Elymus, including E. elymoides (p. 318), E. multisetus (p. 318) (see E. ×hansenii, p. 340), E. trachycaulus, and E. stebbinsii. These hybrids often appear at least partially fertile. Elymus glaucus can also form intergeneric hybrids with Leymus and Hordeum (see ×Elyleymus, p. 343, and ×Leydeum, p. 368).

The following three subspecies appear to be morphologically, ecologically, and geographically distinct. Plants found at elevations of up to 2200 m along the Pacific coast, with hairy leaf blades and lemma awns usually shorter than 20 mm, have been called subsp. jepsonii (Burtt Davy) Gould, but Wilson et al. (2001) demonstrated that such plants are neither genetically nor ecologically distinct from those with glabrous leaf blades; they are included here in subsp. glaucus.

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