Elymus macgregorii
Elymus repens
early wild-rye
chiendent, chiendent rampant, couch grass, creeping wild-rye, quack grass, quackgrass wildrye
40-120 cm, erect or slightly decumbent;
nodes 4-8, mostly exposed, glabrous.
50-100 cm.
evenly distributed;
sheaths usually glabrous, rarely villous;
auricles 2-3 mm, usually purplish black when fresh, sometimes light brown;
ligules shorter than 1 mm;
blades 7-15 mm wide, lax, dark glossy green under the glaucous bloom, adaxial surfaces usually glabrous, occasionally villous.
sometimes somewhat basally concentrated;
sheaths pilose or glabrous proximally;
auricles 0.3-1 mm;
ligules 0.25-1.5 mm;
blades 6-10 mm wide, usually flat, abaxial surfaces glabrous or sparsely pilose, adaxial surfaces usually sparsely pilose over the veins, sometimes glabrous, veins smooth, widely spaced, primary veins prominent, separated by the secondary veins.
4-12 cm long, (1.7)2.2-3(4)4 cm wide, erect, exserted, with (6)9-16(20) nodes and 2 spikelets at all or most nodes, sometimes with 3 at some nodes;
internodes 4-7 mm long, about 0.3 mm thick and 2-angled at the thinnest sections, usually glabrous or scabridulous beneath the spikelets.
5-15 cm long, 0.5-1.5 cm wide, erect, usually with 1 spikelet per node, occasionally with 2 at a few nodes;
internodes 4-6(9.5) mm long, 0.5-1.2 mm wide, smooth or scabrous, glabrous, evenly puberulent, or sparsely pilose, hairs to 0.3 mm.
10-15 mm, strongly divergent, glaucous, maturing to pale yellowish brown, with (2)3-4 florets, lowest florets functional;
disarticulation below the glumes and each floret, the lowest floret often falling with the glumes.
10-27 mm, appressed to ascending, with 4-7 florets;
disarticulation above the glumes, beneath each floret.
subequal, entire, the basal 1-3 mm terete or subterete, indurate, without evident venation, moderately bowed out, glume bodies 8-16 mm long, 1-1.8 mm wide, linear-lanceolate, widening or parallel-sided above the base, (2)4-5(8)-veined, usually glabrous, occasionally hirsute, sometimes scabrous, margins firm, awns (10)15-20(25) mm, straight except the awns of the lowest spikelets occasionally contorted;
lemmas 6-12 mm, usually glabrous, sometimes scabrous, occasionally villous, awns (15)20-30 mm, straight;
paleas 6-10 mm, apices obtuse;
anthers 2-4 mm.
oblong, glabrous, keeled distally, keels inconspicuous and smooth proximally, scabrous and conspicuous distally, lateral veins inconspicuous, hyaline margins present in the distal 1/2, apices acute, unawned or awned, awns to 3 mm;
lower glumes 8.8-11.4 mm, 3-6-veined;
upper glumes 7-12 mm, 5-7-veined;
lemmas 8-12 mm, glabrous, mostly smooth, sometimes scabridulous distally, unawned or with a 0.2-4(10) mm awn, awns straight;
paleas 7-9.5 mm, keels ciliate from 1/2 to almost the entire length, apices emarginate, truncate, or rounded;
anthers 4-7 mm.
usually mid-May to mid-June.
= 28.
= 22, 42.
Elymus macgregorii
Elymus repens
Elymus macgregorii grows in moist, deep, alluvial or residual, calcareous or other base-rich soils in woods and thickets, mostly east of the 100th Meridian in the contiguous United States. It used to be confused with E. glabriflorus (p. 296) or E. virginicus (p. 298), but it reaches anthesis about a month earlier than sympatric populations of these species. In most of its range, E. macgregorii has purplish black auricles; light brown auricles may be locally abundant, particularly in populations at the limits of its range.
Elymus macregorii hybridizes with several species, but especially E. virginicus and E. hystrix (p. 316) (Campbell 2000). Western plants often have smaller, more condensed spikes and distinctly villous leaves, suggesting a transition to E. virginicus var. jejunus (p. 300). Transitions to E. virginicus var. jejunus can also be recognized to the north, where the dates of anthesis are delayed, but even in Maine, E. macgregorii reaches anthesis about 10 days earlier than E. virginicus (Campbell and Haines 2002). Plants with villous lemmas grow at scattered locations; they have not been reported in distinct habitats, nor in large enough populations to warrant taxonomic recognition.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Elymus repens is native to Eurasia; it is now established through much of the Flora region, extending from Alaska to Greenland and south to California, Texas, and North Carolina. It grows well in disturbed sites, spreading rapidly via its long rhizomes, as well as by seed. It is also drought tolerant. Although it is listed a noxious weed in several states, it provides good forage. It differs from E. hoffmannii (see next) in having widely spaced, unequally prominent leaf veins and, usually, shorter awns.
Godley (1947) demonstrated that lemma awn development, glaucousness, and the pubescence of the rachises are each effectively controlled by single genes. Long-awned plants are homozygous recessive, and awn-tipped plants homozygous dominant; glaucousness is dominant over non-glaucousness, and glabrous rachises over pubescent rachises. Awned plants appear to be established along the coasts of Newfoundland and Nova Scotia. They have generally been identified as Agropyron pungens (Pers.) Roem. & Schult., a species that has obtuse, mucronate lemmas.
Elymus repens is almost always a hexaploid. Most studies indicate that its genomic constitution is StStH, but Mason-Gamer (2001) demonstrated that it is genetically more complex than is implied by such a simple formula.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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