Flora of North America species comparison

Elymus hystrix grows in dry to moist soils in open woods and thickets, especially on base-rich slopes and small stream terraces. It grows throughout most of temperate eastern North America, extending west to Manitoba and Oklahoma, but is absent from the southern portion of the coastal plain.

Plants with pubescent lemmas have been recognized as Elymus hystrix var. bigelovianus (Fernald) Bowden. These occur infrequently north of a line from South Dakota through Kentucky to New Jersey, and are often mixed with the typical variety; uniform populations are known in the northeastern United States. Plants with pubescent blades are also more prevalent to the north. Elymus hystrix hybridizes with most eastern species of Elymus. Introgression may account for the considerable variation in glume development and spikelet appression among these species. Lack of glumes may be a recessive character, with even slight glume development indicating introgression (Church 1967b). Plants with relatively well-developed, subequal glumes are presumed to be of hybrid origin. Such plants include most material from the Carolina piedmont region, where E. glabriflorus (p. 296) is the most likely source of introgression. The relatively frequent hybrids with E. virginicus (p. 298) are usually sterile, but Church (1967b) made crosses through three segregating generations. Within the ranges of E. diversiglumis (p. 316), E. svensonii (p. 314), and E. churchii (p. 314;, there appear to be frequent introgressants between these species and E. hystrix. Further east, especially in the Appalachian regions of North Carolina, Virginia, West Virginia, and Maryland (including the shale barrens and nearby), there are scattered plants of E. hystrix with curving awns and, in a few cases, appressed spikelets (Campbell 2002). Whether these represent occasional variation within the E. hystrix gene pool, or whether they are outlying remnants of introgression with E. canadensis (p. 303) during a past eastward extension, is unknown.

(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.)