Elymus hystrix
Elymus riparius
bottlebrush grass, eastern bottle-brush grass, glumeless wlldrye
eastern riverbank wild-rye, river wild-rye, riverbank wildrye, élyme des rivages
50-140 cm, usually erect, occasionally geniculate below;
nodes 4-8, exposed or concealed, glabrous.
70-160 cm, erect, sometimes rooting at the lower nodes;
nodes 5-10, mostly concealed, glabrous.
evenly distributed;
sheaths usually glabrous, occasionally pilose, often purplish;
auricles usually present, 0.5-3 mm, brown to black;
ligules 1-2(3) mm;
blades 4-16 mm wide, lax, usually deep glossy green, adaxial surfaces pilose or scabridulous.
evenly distributed;
sheaths usually glabrous or scabridulous, often reddish brown;
auricles absent or to 2 mm, brown;
ligules shorter than 1 mm;
blades (5)8-15(25) mm wide, flat, lax, dull green, drying to grayish, adaxial surfaces glabrous or scabrous.
7-20 cm long, 4-7 cm wide, more or less erect, usually with 2 spikelets per node, rarely with 3 at some nodes;
internodes (3)4-8(10) mm long, (0.1)0.2-0.3(0.4) mm thick at the thinnest sections, flexuous, usually glabrous, sometimes scabrous or hirsute, usually with green lateral bands.
7-25 cm long, 2-4 cm wide, nodding, exserted, usually with 2 spikelets per node, rarely with 3 at some nodes;
internodes 3-5(8) mm long, 0.2-0.35 thick at the thinnest sections, usually glabrous below the spikelets.
10-18 mm, strongly divergent to patent at maturity, with (1)2-4(6) florets, lowest florets functional;
disarticulation above the glumes, beneath each floret.
10-20 mm, strongly divergent, with 2-3(4) florets, lowest florets functional;
disarticulation above the glumes and beneath each floret.
usually vestigial, sometimes 1-3 mm long, about 0.1 mm wide, subulate, entire, with no evident veins, occasionally to 10(20) mm long including the undifferentiated awns and differing in length by more than 5 mm, 0.1-0.2 mm wide, setaceous, tapering from the base, usually glabrous, occasionally appressed-puberulent to strigose, sometimes scabrous, usually straight, rarely somewhat curving, margins firm;
lemmas 8-11 mm, usually glabrous, occasionally appressed-puberulent to strigose, especially near the margins and apices, awns (12)20-40(47) mm, usually straight, rarely somewhat curving;
paleas 7-11 mm, obtuse or truncate, occasionally emarginate;
anthers 2.5-5 mm.
equal or subequal, 14-30 mm including the sometimes undifferentiated awn, the basal 0.5-2 mm terete, indurate, straight or nearly so, veins not evident, glume bodies 9-17 mm long, (0.3)0.5-0.8(1) mm wide, linear-setiform, entire, widening or parallel-sided above the base, 2-3(4)-veined, usually hispidulous or scabrous, rarely glabrous, margins firm, awns (5)8-18 mm, straight;
lemmas 7-14 mm, usually hispidulous, sometimes scabrous, awns 15-35 mm, usually straight, those of the basal spikelets occasionally contorted;
paleas 6-9 mm, usually acute, sometimes obtuse to truncate, bidentate;
anthers 2-2.7 mm.
mid-June to early July.
late June to late July.
= 28.
= 28.
Elymus hystrix
Elymus riparius
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 riparius grows in moist, usually alluvial and often sandy soils in woods and thickets, usually along larger streams and occasionally along upland ditches. It is widespread in most of temperate east-central North America. It is rare in southern Ontario and Quebec, and the eastern Great Plains. It is virtually absent from the southeastern coastal plain.
Elymus riparius is relatively uniform and distinct. It is sometimes confused with E. canadensis (see next), but that species has curving awns. It hybridizes occasionally with several other taxa, especially E. virginicus var. virginicus (p. 300) and E. hystrix (p. 316), but the hybrids produce only late, depauperate spikes or none at all (e.g., Church 1958).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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