13.17  LEYMUS Hochst.

Mary E. Barkworth

Plants perennial; sometimes cespitose, often rhizomatous. Culms 10–350 cm, erect, with extravaginal branching. Leaves basal or evenly distributed; sheaths open; auricles usually present; ligules membranous, truncate to rounded; blades often stiff, adaxial surfaces usually with subequal, closely spaced, prominently ribbed veins, sometimes with unequal, widely spaced, not prominently ribbed veins. Inflorescences usually distichous spikes with 1–8 spikelets per node, sometimes panicles with (2)3–35 spikelets associated with each rachis node; rachises with scabrous or ciliate edges; internodes 3.5–12(15) mm. Spikelets 1/2–3 3/4 times the length of the rachis internodes, usually sessile, sometimes pedicellate, pedicels to 5 mm, appressed to ascending, with 2–12 florets, the terminal floret usually reduced; disarticulation above the glumes, beneath the florets. Glumes usually 2, usually equal to subequal, the lower or both glumes sometimes reduced or absent, lanceolate and narrowing in the distal 1/4, or lanceolate to subulate and tapering from below midlength, pilose or glabrous, sometimes scabrous, 0–3(7)-veined, veins evident at least at midlength, sometimes keeled, keels straight or almost so, apices acute, acuminate, or tapering to an awnlike tip, if distinctly awned, awns to 4 mm; lemmas glabrous or with hairs, sometimes scabrous distally, inconspicuously 5–7-veined, rounded over the back proximally, sometimes keeled distally, keels not conspicuously scabrous distally, apices acute, unawned or awned, awns usually to 7 mm, sometimes 16–33 mm, straight; paleas slightly shorter than to slightly longer than the lemmas, keels usually scabrous or ciliate on the distal portion, sometimes throughout; lodicules 2, shortly hairy, lobed; anthers 3, 2.5–10 mm. Caryopses with hairy apices. x = 7. Haplomes Ns, Ns or Xm. Name an anagram of Elymus.

Yen et al. (2009) presented a synopsis of Leymus in which they recognized 61 species. All the species are native to temperate regions in the Northern Hemisphere, the greatest diversity being present in eastern Asia, with North America being a secondary center. They recognized three sections in the genus. Sect. Leymus has long, relatively thick rhizomes and lanceolate lemmas. Its members grow in open, sunny areas on the shores of seas, lakes, and rivers and in sand dunes. Species of Sect. Anisopyrum may lack rhizomes but, in those that have them, the rhizomes are thinner. The species also differ from those of sect. Leymus in having subulate glumes and, in a few instances, highly reduced glumes. Like the species of sect. Leymus, members of sect. Anisopyrum grow in open, sunny locations but in steppe and meadow environments rather than bodies of water pr and dunes. Sect. Silvicola includes most of the species that used to be placed in Hystrix, but not the type species of that genus, Elymus hystrix. They differ from members of the other two sections in having no or only vestigial glumes and in growing in shady, forested areas. They also differ in growing in prefering more acidic soils than members of the other sections.

Phylogenetic analysis by Sha et al. (2008) is not strongly supportive of this sectional treatment. Whether this reflects their reliance on the ITS region, inadequate sampling, or the polyphyletic origin of the characters used to delimit the sections is not clear.

Members of sects. Leymus and Anispyrum are used for soil stabilization and forage. All the species are self-incompatible, outcrossing polyploids. One of the haplomes present is the Ns genome; this genome is also found in Psathyrostachys, most species of which are diploids. There is disagreement concerning the second haplome. Wang and Jensen (1994) argued there are two different haplomes present, the origin of the second one being unknown and designated Xm.  Bödvarsdóttir and Anamthawat-Jónsson (2003; Anamthawat-Jónsson 2005) found no molecular probes that would distinguish between the two genera, from which they argued that Leymus is a segmental allopolyploid with only one basic haplome, Ns.  Morphologically,  Psathyrostachys and Leymus, are very similar, the major differences being that Psathyrostachys is never rhizomatous, has disarticulating rachises, and, usually, distinctly awned lemmas.

Of the 17 species treated here, 11 are native to the Flora region, 5 are introduced, and 2 are naturally occurring hybrids.

Leymus arenarius and L. mollis are sometimes mistaken for Ammophila, which grows in the same habitats and has a similar habit. Ammophila differs from Leymus, however, in having only one floret per spikelet.

In most species of Leymus, at least some of the spikelets are on pedicels up to 2 mm long. Despite this, it is customary to identify the inflorescence of such species as a spike rather than a raceme, as is done in this treatment. Culm thicknesses are measured on the lower internodes. Descriptions of rachis nodes, unless stated otherwise, apply to the internodes at midspike.

SELECTED REFERENCES Anamthawat-Jσnsson, K. 2005. The Leymus Ns-genome. Czech J. Genet. Pl. Breed. 41(Special Issue):13–20; Barkworth, M.E. and R.J. Atkins. 1984. Leymus Hochst. (Gramineae: Triticeae) in North America: Taxonomy and distribution. Amer. J. Bot. 71:609–625; Bowden, W.M. 1957. Cytotaxonomy of section Psammelymus of the genus Elymus. Canad. J. Bot. 35:951–993; Bowden, W.M. 1959. Chromosome numbers and taxonomic notes on northern grasses: I. Tribe Triticeae. Canad. J. Bot. 37:1143–1151; Hole, D.J., K.B. Jensen, R.R.-C. Wang, and S.M. Clawson. 1999. Molecular analysis of Leymus flavescens and chromosome pairing in Leymus flavescens hybrids (Poaceae: Triticeae). Int. J. Plant Sci. 160:371–376; Jensen, K.B. and R.R.-C. Wang. 1997. Cytological and molecular evidence for transferring Elymus coreanus from the genus Elymus to Leymus and molecular evidence for Elymus californicus (Poaceae: Triticeae). Int. J. Pl. Sci. 158:872–877; Mason-Gamer, R.J. 2001. Origin of North American Elymus (Poaceae:Triticeae) allotetraploids based on granule-bound starch synthase gene sequences. Syst. Bot. 26:757–768; Sha, L-N., R-W. Yang, X. Fang, X-L Wang, and Y-H Zhou. (2008). Phylogenetic analysis of Leymus (Poaceae: Triticeae) inferred from nuclear rDNA ITS sequences. Biochemical Genetics 46: 605-619 [DOI 1007/s10528-008-9175-5]; Tsvelev, N.N. 1976. Zlaki SSSR. Nauka, Leningrad [St. Petersburg], Russia. 788 pp.; Tsvelev, N.N. 1995. Leymus. Pp. 300–306 in J.G. Packer (ed., English edition). Flora of the Russian Arctic, vol. 1, trans. G.C.D. Griffiths. University of Alberta Press, Edmonton, Alberta, Canada. 330 pp. [English translation of A.I. Tolmachev (ed.). 1964. Arkticheskaya Flora SSSR, vol. 2. Nauka, Leningrad [St. Petersburg], Russia. 272 pp.; Wang, R.R.-C. and K.B. Jensen. 1994. Absence of J genome in Leymus species (Poaceae: Triticeae): Evidence from DNA hybridization and meiotic pairing. Genome 37:231–235; Wang, R.R.-C., J.-Y. Zhang, B.S. Lee, K.B. Jensen, M. Kishi, and H. Tsuijimoto. 2006. Variations in abundance of 2 repetitive sequences in Leymus and Psathyrostachys species. Genome 49:511–519; Yen, C., J.-L. Yang, and B.R. Baum. Synopsis of Leymus Hochst. (Triticeae: Poaceae), Journal of Systmatics and Evolution 47:67-86; Zhang, H.B. and J. Dvorαk. 1991. The genome origin of tetraploid species of Leymus (Poaceae: Triticeae) inferred from variation in repeated nucleotide sequences. Amer. J. Bot. 78:871–884.

1. Glumes absent or shorter than 1 mm; lemmas awned, awns 16–33 mm long.................. 17. L. californicus

1. Glumes developed, 3+ mm long, at least 1 on each spikelet; lemmas unawned or awned, awns to 7 mm long.

2. Glumes flat or rounded on the back, tapering from midlength or above, flexible, the central portion scarcely thicker than the margins..................................................................................... 3. L mollis

2. Glumes keeled, at least distally, tapering from below midlength, stiff, the central portion thicker than the margins.

3. Anthers usually indehiscent; plants rhizomatous, restricted to coastal regions from British Columbia to California.

4. Glumes pubescent distally; lemmas awned, awns to 4 mm long; inflorescences spikes, not branched................................................................................................. 4. L Χvancouverensis

4. Glumes glabrous; lemmas acute to awned, awns to 1.8 mm long; inflorescences sometimes with strongly ascending branches.......................................................................... 11. L Χmultiflorus

3. Anthers dehiscent; plants rhizomatous or cespitose, widespread, including coastal regions from British Columbia to California.

6. Inflorescences with 2–4 branches to 6 cm long at the proximal nodes; culms 115–350 cm tall 10. L condensatus

6. Inflorescences usually without branches, sterile hybrids sometimes with branches to 3 cm long; culms 10–270 cm tall.

7. Lemmas densely hairy, hairs 0.7–3 mm long, occasionally glabrate.

8. Lemmas awned, awns 2–4 mm long; lemma hairs 0.7–2.5 mm long............. 15. L innovatus

8. Lemmas unawned or the awns to 2 mm long; lemma hairs 2–3 mm long...... 16. L flavescens

7. Lemmas usually wholly or partly glabrous, or if hairy, the hairs shorter than 0.5(0.8) mm.

9. Leaves equaling or exceeding the spikes; culms 10–30(60) cm tall; spikes 2–8 cm long, with 1–2 spikelets per node; plants of California coastal bluffs.............................. 5. L. pacificus

9. Leaves exceeded by the spikes; culms 35–270 cm tall; spikes 3–35 cm long, with 1–8 spikelets per node; plants widespread in the western part of the Flora region, including the coastal bluffs of California.

10.  Plants cespitose, not or weakly rhizomatous, culms several to many together.

11.  Spikes with 2–7 spikelets per node; blades 3–12 mm wide; culms (70)100–270 cm tall............................................................................................... 12. L cinereus

11.  Spikes with 1 spikelet at the distal nodes, often at all nodes, sometimes with 2(3) at the lower nodes; blades 1–6 mm wide; culms 35–140 cm tall.

12.  Blades with 5–9 adaxial veins; lemma awns to 2.5 mm long........... 13. L salina

12.  Blades with (9)11–17 adaxial veins; lemma awns 1.3–7 mm long............. 14. L ambiguus

10.  Plants rhizomatous, culms solitary or a few together.

13. Culms 1–3 mm thick; glumes 4–16 mm long.

14.  Spikes with 1 spikelet at all or most nodes, sometimes with 2 at a few nodes; lemma awns 2.3–6.5 mm long; culms 35–55 cm tall..................... 6. L simplex

14.  Spikes with 2+ spikelets at most nodes; lemma awns to 3 mm long; culms 45–125 cm tall.

15.  Adaxial surfaces of the blades usually with closely spaced, prominently ribbed, subequal veins; calluses usually glabrous, occasionally with a few hairs about 0.1 mm long................................................... 7. L. triticoides

15.  Adaxial surfaces of the blades usually with widely spaced, not prominently ribbed veins, the primary veins evidently larger than the intervening secondary veins; calluses with hairs about 0.2 mm long..... 8. L. multicaulis

13. Culms 2.5–12 mm thick; glumes 10–30 mm long.

16.  Spikelets 3–8 per node; lemmas hairy proximally, glabrous distally........... 1. L. racemosus

16.  Spikelets 2–3 per node; lemmas glabrous or hairy their whole length.

17.  Anthers 6–9 mm long; blades 3–11 mm wide; glumes with hairs to 1.3 mm long; plants established around the Great Lakes and the coast of Greenland, also found at a few other scattered locations, including western North America, sometimes cultivated............................................ 2. L arenarius

17. Anthers 3–5 mm long; blades 5–7 mm wide; glumes glabrous, sometimes scabrous........................................................................... 9. L. angustus

1. Leymus racemosus (Lam.) Tzvelev

Mammoth Wildrye

Plants not or only weakly cespitose, strongly rhizomatous. often glaucous. Culms 50–100 cm tall, 8–12 mm thick, solitary or a few together, mostly smooth and glabrous, scabridulous or pubescent below the spikes, hairs to 0.5 mm. Leaves exceeded by the spikes; ligules 1.5–2.5 mm; blades 20–40 cm long, 8–20 mm wide. Spikes 15–35 cm long, 10–20 mm wide, dense, with 3–8 spikelets per node; internodes 8–11 mm, hairy, hairs on the surfaces to 1 mm, on the edges to 1.5 mm. Spikelets 12–25 mm, sessile, with 4–6 florets. Glumes 12–25 mm long, to 2 mm wide, usually exceeding the lemmas, linear-lanceolate at the base, tapering from below midlength, stiff, glabrous at least at the base, the central portion thicker than the margins, keeled and subulate distally, 1-veined, veins inconspicuous at midlength; lemmas 15–20 mm, pubescent proximally, glabrous distally, tapering to an awn, awns 1.5–2.5 mm; palea keels usually glabrous, sometimes ciliate distally; anthers about 5 mm, dehiscent. 2n = 28.

Leymus racemosus is native to Europe and central Asia, where it grows on dry, sandy soils. It has been introduced into the Flora region, and collected at various locations, particularly in the northwestern contiguous United States; it is not clear how many of the populations represented by these specimens are still extant. Tsvelev (1976) recognized 4 subspecies. Because there are few North American specimens, and these are incomplete, no attempt has been made to determine to which subspecies the North American plants belong.

2. Leymus arenarius (L.) Hochst.

European Dunegrass, Ιlyme des Sables d’Europe

Plants weakly cespitose, rhizomatous, strongly glaucous. Culms 50–150 cm tall, (2)3–6 mm thick, usually glabrous throughout, occasionally pubescent distally to 5 mm below the spike. Leaves exceeded by the spikes; ligules 0.3–2.5 mm; blades 3–11 mm wide, with 15–40 adaxial veins. Spikes 12–35 cm long, 15–25 mm wide, usually with 2 spikelets per node; internodes 8–12 mm, surfaces glabrous, edges ciliate. Spikelets 12–30 mm, with 2–5 florets. Glumes 12–30 mm long, 2–3.5 mm wide, lanceolate, tapering from below midlength, stiff, glabrous towards the base and usually distally, sometimes pubescent distally, the central portion thicker than the margins, 3(5)-veined at midlength, keeled or rounded over the midvein, midveins and sometimes the margins with hairs to about 1.3 mm, apices acuminate; lemmas 12–25 mm, densely villous, hairs 0.3–0.7 mm, 5–7-veined, acute, occasionally awned, awns to 3 mm; anthers 6–9 mm, dehiscent. 2n = 56.

Leymus arenarius is native to Europe. It has become established in sandy habitats around the Great Lakes and the coast of Greenland. It has also been found at a few other widely scattered locations. It is sometimes cultivated, forming large, attractive, blue-green clumps, but its tendency to spread may be undesirable.

3. Leymus mollis (Trin.) Pilg.

American Dunegrass, Sea Lymegrass, Ιlyme des Sables d’Amerique, Seigle de Mer

Plants not cespitose, strongly rhizomatous, occasionally slightly glaucous. Culms 12–170 cm tall, 3–6 mm thick, usually densely pubescent below the spikes for 10–40+ mm. Leaves exceeded by the spikes; auricles to 0.7 mm; ligules 0.2–2.5 mm; blades 10–94 cm long, 3–15 mm wide, adaxial surfaces scabridulous to scabrous, 20–40-veined, veins subequal, prominently ribbed, closely spaced. Spikes 5–34 cm long, 10–20 mm wide, with 3–33 nodes, usually with 2 spikelets per node; internodes 4.5–9.5 mm, surfaces and edges similar, soft, hairs on the surfaces 0.1–0.5 mm, on the edges to 0.7 mm. Spikelets 15–34 mm, with 3–6 florets. Glumes 9–34 mm long, 1.5–4 mm wide, lanceolate, tapering from midlength or above, flat or rounded on the back, flexible, usually strigillose to pilose or villous, rarely almost glabrous, the central portion scarcely thicker than the margins, 3(5)-veined at midlength, apices acute; lemmas 11–20 mm, densely hairy, hairs 0.5–1 mm, soft, apices acute, unawned; anthers 4–9 mm, dehiscent.

Leymus mollis is native to Asia and North America. It is treated here as having two very similar subspecies that have somewhat different ranges. The subspecies are sometimes treated as separate species, but they may be little more than environmentally induced variants. Both subspecies grow primarily on coastal beaches, close to the high tide line, and along some inland waterways, particularly in the arctic. Reports of Leymus ajanensis (V.N. Vassil.) Tzvelev from North America are based on specimens of L. mollis (D. Murray, University of Alaska, pers. comm. 2006).

1.  Spikes 12–34 cm long, with 12–33 nodes; basal blades 5–15 mm wide; culms 50–170 cm tall           subsp. mollis

1.  Spikes 5–13(16) cm long, with 3–14 nodes; basal blades 3–8 mm wide; culms 12–70 cm tall             subsp. villosissimus

Leymus mollis (Trin.) Pilg. subsp. mollis

Rhizomes 4–6 mm thick. Culms (50)70–170 cm. Basal blades 22–94 cm long, 5–15 mm wide. Spikes 12–34 cm, with 12–33 nodes. Glumes 13–34 mm long, 3–4 mm wide, often longer than the lemmas, usually pilose, sometimes almost glabrous. 2n = 28.

In the Flora region, Leymus mollis subsp. mollis grows primarily on the west coast; on the east coast, it grows in New Brunswick and Nova Scotia, particularly along the St. Lawrence River, and on the coast of Greenland. It does not grow along the arctic coast. Outside the Flora region, it is native in the coastal region of eastern Asia, growing primarily along the coast and in the mouths of larger rivers, and on the shores of large lakes near the coast from the Korean Peninsula to the Kamchatka Peninsula. It was introduced to Iceland, but is now rare there.

Leymus Χvancouverensis is thought to be a hybrid between L. mollis subsp. mollis and L. triticoides, although its range extends beyond the current range of L. triticoides.

Leymus mollis subsp. villosissimus (Scribn.) Α. Lφve

Rhizomes about 2 mm thick. Culms 12–70 cm. Basal blades 10–31 cm long, 3–8 mm wide. Spikes 5–13(16) cm, with 3–14 nodes. Glumes 9–14(21) mm long, 1.5–2.5 mm wide, often longer than the lemmas, villous. 2n = 28.

Leymus mollis subsp. villosissimus is an arctic taxon found primarily in eastern Siberia, Alaska, and northwestern Canada. It grows mostly on arctic coasts, but is also known from a few inland locations.

4. Leymus Χvancouverensis (Vasey) Pilg.

Vancouver Wildrye

Plants not cespitose, rhizomatous, green or slightly glaucous. Culms 60–122 cm tall, 2–3.5 mm thick, sparsely to densely pubescent below the spike. Leaves exceeded by the spikes; auricles to 1 mm; ligules 0.4–1.2 mm; blades to 9 mm wide, veins promimently ribbed, subequal, closely spaced. Spikes 7–32 cm long, 7–11 mm wide, sometimes glaucous, often purplish or green with traces of purple, with 1–2 spikelets per node; internodes 8–12 mm, surfaces hairy distally, hairs 0.1–0.3 mm, edges ciliate, hairs to 1 mm, coarser than the surficial hairs. Spikelets 15–20 mm, with 2–6 florets. Glumes 9–28 mm long, 1.5–4 mm wide, lanceolate, glabrous towards the base, pubescent distally, midveins glabrous or with hairs to about 1.3 mm, stiff, keeled or flat proximally, keeled distally, the central portion thicker than the margins, 3(5)-veined at midlength, tapering from below midlength to an awn, awns to 4 mm; lemmas 8–10 mm, usually completely glabrous, margins and apices sometimes pubescent, apices tapering to an awn, awns to 4 mm; anthers 3.3–7.3 mm, indehiscent. 2n = 28, 42.

Leymus Χvancouverensis grows at scattered locations on beaches along the Pacific coast, from southern British Columbia to California. It is a sterile hybrid, probably between L. mollis and L. triticoides (Bowden 1957). The northern populations are outside the current range of L. triticoides.

5. Leymus pacificus (Gould) D.R. Dewey

Pacific Wildrye

Plants not cespitose, strongly rhizomatous. Culms 10–30(60) cm tall, 1–2 mm thick, solitary or a few together, glabrous or sparsely pubescent near the nodes. Leaves equaling or exceeding the spikes; sheaths glabrous; auricles to 1.4 mm; ligules 0.2–0.3 mm, truncate, erose; blades 10–30 cm long, 2–4 mm wide, abaxial surfaces glabrous, adaxial surfaces scabrous, veins about 15, subequal, prominently ribbed. Spikes 2–8 cm long, 7–12 mm wide, with 1–2 spikelets per node; internodes 3.5–4 mm, surfaces glabrous and smooth, edges weakly scabrous distally. Spikelets 12–15 mm, with 4–6 florets. Glumes subequal, (5)7–15 mm long, 0.5–2.5 mm wide, narrowly lanceolate, tapering from near the base, stiff, keeled, the central portion thicker than the margins, bases mostly glabrous, margins ciliate, 1–3(5)-veined, veins inconspicuous at midlength; calluses scarcely developed, glabrous; lemmas 7–11 mm, glabrous, smooth, apices acute to awn-tipped, awns to 0.8 mm; anthers 3–4 mm, dehiscent. 2n = 28.

Leymus pacificus is found on coastal bluffs from Mendocino to Santa Barbara counties, California. It is poorly represented in herbaria. In some years it grows almost entirely vegetatively, often being represented by scattered innovations with somewhat curved leaves.

6. Leymus simplex (Scribn. & T.A. Williams) D.R. Dewey

Alkali Wildrye

Plants not cespitose, strongly rhizomatous, often glaucous. Culms 35–75 cm tall, 1–2.5 mm thick, solitary or a few together, glabrous or sparsely pubescent near the nodes. Leaves exceeded by the spikes; sheaths glabrous, smooth; auricles infrequently present, to 0.8 mm, the auricular location often with hairs to 2 mm; ligules 0.3–0.5 mm, truncate, erose; blades 4–29 cm long, 1–2(5) mm wide, flat, becoming involute when dry, stiff, adaxial surfaces scabrous, with scattered hairs to 2 mm, veins 7–11, subequal, prominently ribbed. Spikes 1.5–25 cm long, 4–10 mm wide, with 1 spikelet per node at midspike, sometimes with 2 at the lower nodes; internodes 7–12 mm, surfaces glabrous or strigillose, edges ciliate, cilia to 1 mm. Spikelets 16–25 mm, pedicellate, pedicels 1–2(5) mm, with 3–12 florets. Glumes subequal, 8–12 mm long, 0.5–1.5 mm wide, subulate, tapering from about 1/4 of their length, stiff, glabrous at least at the base, the central portion thicker than the margins, keeled, 0–1(3)-veined, veins inconspicuous at midlength; lemmas 7–12 mm, glabrous, awned, awns 2.3–6.5(12) mm; anthers 3.7–4.5 mm, dehiscent. 2n = 28.

Leymus simplex is found in meadows and drifting sand in southern Wyoming, and along the Green River in northeastern Utah.

1.  Culms 55–75 cm tall; racemes 10–25 cm long; internodes 10–12 mm    var. luxurians

1.  Culms 35–55 cm tall; racemes 1.5–13 cm long; internodes 7–9 mm       var. simplex

Leymus simplex var. luxurians (Scribn. & T.A. Williams) Beetle

Culms 55–75 cm tall, 2–2.5 mm thick. Spikes 10–25 cm long; internodes 10–12 mm. Spikelets 20–25 mm, with 6–12 florets.

Leymus simplex var. luxurians grows at a few locations in Wyoming. It sometimes grows close to var. simplex. It may represent clones that have access to more water and/or more nutrients but the absence of intermediate plants suggests a genetic distinction.

Leymus simplex (Scribn. & T.A. Williams) D.R. Dewey var. simplex

Culms 35–55 cm tall, 1–2 mm thick. Spikes 1.5–13 cm long; internodes 7–9 mm. Spikelets 16–22 mm, with 3–6 florets.

Leymus simplex var. simplex is found throughout the range of the species, sometimes in close proximity to var. luxurians. The two may be environmentally induced variants, but the lack of intermediates suggests a genetic distinction.

7. Leymus triticoides (Buckley) Pilg.

Beardless Wildrye

Plants not cespitose, strongly rhizomatous. Culms 45–125 cm tall, 1.8–3 mm thick, solitary or a few together. Leaves exceeded by the spikes, often basally concentrated; sheaths glabrous or hairy, hairs 0.5–1 mm; auricles to 1 mm; ligules 0.2–1.3 mm, truncate, erose; blades 10–35 cm long, 3.5–10 mm wide, flat to involute, usually stiffly ascending, adaxial surfaces usually scabrous, often also sparsely hairy, hairs to 0.8 mm, most abundant proximally, veins 11–27, closely spaced, subequal, prominently ribbed. Spikes 5–20 cm long, 5–15 mm wide, with 2 spikelets at midspike, sometimes 1 or 3 at other nodes; internodes 5–11.5 mm, usually mostly smooth and glabrous, sometimes strigillose distally, edges ciliate, cilia to 0.4 mm. Spikelets 10–22 mm, with 3–7 florets. Glumes 5–16 mm long, 0.5–1.2 mm wide, bases not overlapping, glabrous and smooth proximally, scabrous distally, tapering from below midlength to the subulate apices, stiff, keeled, the central portion thicker than the margins, 1(3)-veined, veins inconspicuous at midlength; calluses usually glabrous, occasionally with a few hairs about 0.1 mm long; lemmas 5–12 mm, usually glabrous, occasionally sparsely hairy, hairs to 0.3 mm, apices acute, usually awned, awns to 3 mm; anthers 3–6 mm, dehiscent. 2n = 28.

Leymus triticoides grows in dry to moist, often saline meadows. Its range extends from southern British Columbia to Montana, south to California, Arizona, and New Mexico, but its populations are widely scattered. It is not known from Mexico. There is considerable variation within the species, but no pattern of variation suggesting the existence of infraspecific taxa is known. It is very similar to L. multicaulis, strains of which were initially released as L. triticoides by the U.S. Department of Agriculture. The most consistent differences between them appear to be in the venation of the leaf blades and the vestiture of the calluses. Leymus triticoides is also very similar to L. simplex, differing from it in the number of spikelets at the midspike nodes.

Leymus triticoides hybridizes with other species of Leymus; hybrids with L. mollis are called L. Χvancouverensis, those with L. condensatus are called L. Χmultiflorus. Hybrids with L. cinereus are known, but have not been formally named. Plants identified as Elymus arenicolus Scribn. & J.G. Sm. are here included in L. flavescens, but may represent hybrids between L. triticoides and L. flavescens.

8. Leymus multicaulis (Kar. & Kir.) Tzvelev

Manystem Wildrye

Plants somewhat cespitose, rhizomatous. Culms 50–80 cm tall, 1.5–3 mm thick, usually a few together, glabrous, mostly smooth, scabrous beneath the spikes. Leaves exceeded by the spikes; sheaths glabrous, smooth; auricles to 1 mm; ligules 1–2 mm; blades 3–8 mm wide, flat or the margins slightly involute, grayish green, sometimes glaucous, abaxial surfaces smooth, adaxial surfaces glabrous, with both primary and secondary veins, primary veins 5–7, not prominently ribbed. Spikes 5–14 cm long, 6–13 mm wide, with 2–4(6) spikelets per node; internodes 4–6 mm, glabrous or strigillose, hairs about 0.1 mm, edges ciliate, cilia to 0.4 mm. Spikelets 8–15 mm, with 2–6 florets. Glumes 4–10 mm long, to 1 mm wide, stiff, keeled, glabrous, scabrous, the central portion thicker than the margins, bases not overlapping, tapering from below midlength to the subulate apices, inconspicuously 1-veined at midlength; calluses usually with at least some hairs, hairs about 0.2 mm; lemmas 5–9 mm, mostly glabrous and smooth, scabrous distally, apices tapering to an awn, awns 2–3 mm, scabrous; anthers about 3–4 mm, dehiscent. 2n = 42.

Leymus multicaulis is native to Eurasia, extending from the Volga River delta to Xinjiang, China. In its native range, it grows in alkaline meadows and saline soils, and as a weed in fields, near roads, and around human habitations. It is very similar to L. triticoides, and hybrids with that species are highly fertile. A cultivar of L. multicaulis, ‘Shoshone’, that was originally thought to be a productive strain of L. triticoides, has been widely distributed for forage. Leymus multicaulis differs primarily in having both primary and secondary veins in its blades and small hairs on its calluses. Because it has only recently been realized that L. multicaulis has been introduced to North America, its distribution in North America is unknown.

9. Leymus angustus (Trin.) Pilg.

Altai Wildrye

Plants somewhat cespitose, rhizomatous. Culms 60–120 cm tall, 2.5–7 mm thick, solitary or a few together, glabrous or pubescent below the nodes. Leaves exceeded by the spikes, basally concentrated; sheaths smooth, scabridulous, or hairy; auricles to 1 mm; ligules 0.5–1 mm, rounded to obtuse, sometimes erose; blades 15–20 cm long, 5–7 mm wide, glaucous, stiff, involute, abaxial surfaces glabrous, scabridulous, or hairy, adaxial surfaces scabrous, with 7–17 closely spaced subequal veins. Spikes 10–25 cm long, 7–10 mm wide, with 2(3) spikelets per node; internodes 8–10 mm, surfaces strigillose, hairs to 0.3 mm, edges ciliate, cilia to 1 mm. Spikelets 10–19 mm, with 2–3 florets. Glumes 10–13 mm long, 0.5–2.5 mm wide, exceeded by the florets, narrowly lanceolate, tapering from the base, stiff, keeled, the central portion thicker than the margins, (0)1(3)-veined at midlength, bases expanded, overlapping, concealing the base of the lowest floret, scabrous; lemmas 8–13 mm, densely hairy and not glaucous, with hairs to 0.4 mm, or glabrous and glaucous, apices unawned or awned, awns to 2.5 mm; anthers 3–4 mm, dehiscent. 2n = 84.

Leymus angustus is a Eurasian species that, in its native range, grows in alkaline meadows, and on sand and gravel in river and lake valleys. Several cultivars of L. angustus have been developed for use as forage, particularly in Canada. Some of the better known are ‘Prairieland’, ‘Eejay’, and ‘Pearl’. The distribution of L. angustus in the Flora region is not known.

Chen and Zhu (2006) describe Leymus angustus as always being puberulent. Some accessions cultivated under this name by the U.S. Department of Agriculture (Plant Introduction Numbers, including one identified as the cultivar ‘Prairieland’, have glabrous, glaucous lemmas and glumes that tend to exceed the lemmas, suggesting that they belong to another taxon, possibly L. karelinii (Turcz.) Tzvelev, a species for which 2n = 56.

10.  Leymus condensatus (J. Presl) Α. Lφve

Giant Wildrye

Plants cespitose, weakly rhizomatous. Culms 115–350 cm tall, 6–10 mm thick, usually several to many together. Leaves exceeded by the inflorescences; auricles absent; ligules 0.7–6 mm on the basal leaves, 4–7.5 mm on the flag leaves; blades 10–28 mm wide, abaxial surfaces glabrous, smooth, adaxial surfaces scabridulous, veins numerous, subequal or unequal. Inflorescences panicles, 17–44 cm long, 20–60 mm wide, lower nodes with 2–6 branches, branches to 8 cm, ascending, with 5–35 spikelets, upper nodes with pedicellate and sessile spikelets; internodes 3.5–10 mm, glabrous. Spikelets 9–25 mm, usually pedicellate, pedicels 0.8–2 mm, with 3–7 florets. Glumes 6–16 mm long, 0.5–2.5 mm wide, narrowly lanceolate, stiff, keeled, the central portion thicker than the margins, glabrous, smooth proximally, scabrous distally, 0–1(3)-veined, veins inconspicuous at midlength, apices tapering almost imperceptibly into an awn, awns subequal to the glume body; lemmas 7–14 mm, usually glabrous, apices acute, sometimes awned, awns to 4 mm; anthers 3.5–7 mm, dehiscent. 2n = 28, 56.

The native distribution of Leymus condensatus is primarily on dry slopes and in open woodlands of the coastal mountains and offshore islands of California, at elevations of 0–1525 m. It has recently been found alond roadsides in Malheur County, Oregon, probably as part of a roadside planting, and seems likely to spread (B. Wilson, in litt, 2010). Both its large size and paniculate inflorescence tend to make L. condesnatus a distinctive species in the Triticeae. Hybrids between L. condensatus and L. triticoides, known as Leymus Χmultiflorus, are relatively common where the parents are sympatric.

11.  Leymus Χmultiflorus (Gould) Barkworth & R.J. Atkins

Many-Flowered Wildrye

Plants cespitose, rhizomatous. Culms 65–210 cm tall, 3–5 mm thick. Leaves exceeded by the inflorescences; auricles absent; ligules 0.5–2 mm, truncate, erose; blades 6–15 mm wide, both surfaces glabrous, adaxial surfaces with numerous closely spaced, unequal veins. Inflorescences 15–35 cm long, 9–25 mm wide, usually spikes, with 2–6 spikelets per node, occasionally some nodes with 1–2 branches, branches to 60 mm, strongly ascending; internodes 8–10 mm, usually glabrous, sometimes scabrous. Spikelets 17–25 mm, pedicellate, pedicels 0.5–2(5) mm, with 6–9 florets. Glumes 9–25 mm long, differing in length by 1–4 mm, usually exceeding the lowest lemmas, 0.5–2.5 mm wide, subulate to narrowly lanceolate, stiff, keeled, the central portion thicker than the margins, tapering from the bases, glabrous, smooth proximally, scabrous distally, 1(3)-veined, veins inconspicuous at midlength; lemmas 8–12 mm, glabrous, acute to awned, awns to 1.8 mm; anthers about 6 mm, indehiscent. 2n = 42.

Leymus Χmultiflorus is a sterile hybrid between Leymus condensatus and L. triticoides that occurs near the coast of central and southern California.

12.  Leymus cinereus (Scribn. & Merr.) Α. Lφve

Great Basin Wildrye

Plants strongly cespitose, weakly rhizomatous, usually bright green, not glaucous. Culms 70–270 cm tall, 2–5 mm thick, many together, lowest nodes often pubescent, sometimes pubescent up to 1.5 cm below the inflorescence. Leaves exceeded by the spikes; sheaths glabrous or hairy; auricles to 1.5 mm; ligules 1.5–8 mm; blades 15–45 cm long, 3–12 mm wide, strongly involute to flat, abaxial surfaces glabrous, adaxial surfaces scabrous, 11–25-veined, veins subequal, prominently ribbed. Spikes 10–29 cm long, 8–17 mm wide, with 14–28 nodes and 2–7 spikelets per node; internodes 4–9 mm. Spikelets 9–25 mm, with 3–7 florets. Glumes 8–18 mm long, 0.5–2.5 mm wide, subulate distally, stiff, keeled, the central portion thicker than the margins, tapering from below midlength, smooth or scabrous, 0–1(3)-veined, veins inconspicuous at midlength; lemmas 6.5–12 mm, glabrous or hairy, hairs 0.1–0.3 mm, apices acute or awned, awns to 3 mm; anthers 4–7 mm, dehiscent. 2n = 28, 56.

Leymus cinereus grows along streams, gullies, and roadsides, and in gravelly to sandy areas in sagebrush and open woodlands. It is widespread and common in western North America. Leymus cinereus also resembles Psathyrostachys juncea, differing in its non-disarticulating rachises, larger spikelets with more florets, and longer ligules. Spontaneous hybridization between L. cinereus and L. triticoides is known; the hybrids do not have a scientific name. The rhizomes found in some specimens may reflect introgression from L. triticoides through such hybrids.

13.  Leymus salina (M.E. Jones) Α. Lφve

Plants cespitose, sometimes weakly rhizomatous. Culms 35–140 cm tall, 1.5–3 mm thick, several together. Leaves exceeded by the spikes; auricles to 1 mm; ligules 0.1–1 mm, truncate; blades 1–5 mm wide, flat to strongly involute, adaxial surfaces glabrous or sparsely to densely hirsute, with 5–9 prominently ribbed, subequal veins. Spikes 4–14 cm long, 4–11 mm wide, nodes below midspike with 1–2(3) spikelets, distal nodes with 1 spikelet; internodes 3.5–9 mm, surfaces glabrous, edges scabrous or strigillose. Spikelets 9–21 mm, pedicellate, pedicels to 1 mm, with 3–6 florets. Glumes unequal to subequal, to 12.5 mm long, 0.5–3.2 mm wide, subulate, stiff, keeled, the central portion thicker than the margins, tapering from below midlength, 0–1(3)-veined, veins inconspicuous at midlength; lower glumes 0–12 mm; upper glumes 3.5–12.5 mm; lemmas 7–12.5 mm, usually glabrous, sometimes sparsely strigillose, unawned or awned, awns to 2.5 mm; anthers 2.5–7.5 mm, dehiscent.

The three subspecies of Leymus salina differ in their pubescence and geographic distribution, with subsp. salina being the most common of the three. The specific epithet comes from the locality of the type collection: Salina Pass, Utah.

1.  Basal sheaths and blades conspicuously hairy on the abaxial surfaces    subsp. salmonis

1.  Basal sheaths glabrous; blades usually glabrous on the abaxial surfaces.

2.  Blades strongly involute, usually densely hairy just above the ligules subsp. salina

2.  Blades flat or almost flat, not densely hairy above the ligules              subsp. mojavensis

Leymus salina subsp. mojavensis Barkworth & R.J. Atkins

Mojave Wildrye

Culms 35–90 cm. Basal sheaths glabrous; blades flat or almost flat, abaxial surfaces nearly always glabrous, adaxial surfaces scabridulous, not densely hairy above the ligules, occasionally sparsely hairy. Spikes with 1 spikelet at most nodes, 2–3 central nodes with 2 spikelets. 2n = unknown.

Leymus salina subsp. mojavensis grows at scattered locations on steep, north-facing slopes of the New York, Providence, and Clark mountains in California, and of the south rim of the Grand Canyon in Arizona.

Leymus salina (M.E. Jones) Barkworth subsp. salina

Salina Wildrye

Culms 39–102 cm. Basal sheaths glabrous; blades strongly involute, abaxial surfaces glabrous, adaxial surfaces pubescent, usually densely hairy above the ligules. Spikes with 1 spikelet at most nodes, including those at midspike. 2n = 28.

Leymus salina subsp. salina grows on rocky hillsides, primarily in eastern Utah and western Colorado, extending into southern Wyoming and northern Arizona.

Leymus salina subsp. salmonis (C.L. Hitchc.) R.J. Atkins

Salmon Wildrye

Culms 60–140 cm. Basal sheaths conspicuously hairy; blades open to involute, abaxial surfaces conspicuously hairy, adaxial surfaces evenly strigillose to strigose. Spikes with 1–2 spikelets at the central nodes, usually 1 at the distal nodes. 2n = 28.

Leymus salina subsp. salmonis grows at scattered locations on rocky hillsides in the mountains of southern Idaho, Nevada, and western Utah.

14.  Leymus ambiguus (Vasey & Scribn.) D.R. Dewey

Colorado Wildrye

Plants loosely cespitose, occasionally rhizomatous. Culms 60–110 cm tall, 1–1.5 mm thick, many together. Leaves exceeded by the spikes; sheaths glabrous or sparsely pubescent; auricles to 1.1 mm; ligules 0.2–1.2 mm, truncate; blades 2.5–6 mm wide, flat, adaxial surfaces scabridulous, glabrous, veins (9)11–17, unequal, not crowded. Spikes 8–17 cm long, 5–10 mm wide, erect, with 2 spikelets at most nodes; internodes 4–11 mm, surfaces hairy distally, hairs 0.2–0.8 mm, edges ciliate. Spikelets 12–23 mm, with 2–7 florets. Glumes unequal, 0.5–2.5 mm wide, tapering from below midlength to the subulate apices, stiff, keeled, the central portion thicker than the margins, glabrous, scabrous, particularly distally, bases not overlapping, 0–1(3)-veined, veins inconspicuous at midlength; lower glumes 2–9.5 mm; upper glumes 6–14 mm; calluses with hairs, hairs about 0.2 mm; lemmas 8–14.5 mm, glabrous or sparsely strigose, awned, awns 1.3–7 mm; anthers 3.5–7 mm, dehiscent. 2n = 28.

Leymus ambiguus grows on steep, often boulder-strewn hillsides at scattered locations in Colorado and New Mexico.

15.  Leymus innovatus (Beal) Pilg.

Downy Ryegrass, Boreal Wildrye

Plants sometimes cespitose, strongly rhizomatous. Culms 18–105 cm tall, 2–3 mm thick. Leaves exceeded by the spikes; sheaths glabrous or hairy, often most densely hairy in the collar region; auricles to 1.4 mm; ligules 0.1–0.5 mm; blades 2–6 mm wide, involute, abaxial surfaces scabridulous or smooth, adaxial surfaces scabrous, occasionally with scattered hairs to 1.5 mm, veins unequal, not crowded. Spikes 3–16 cm long, 8–20 mm thick, erect, usually well exserted, with 2–3 spikelets per node; internodes 4–6 mm, hairy throughout, edges with hairs to 2.5 mm. Spikelets 10–18 mm, with 3–7 florets. Glumes often unequal, 2.5–12 mm long, 0.5–1 mm wide, hairy, stiff, keeled, the central portion thicker than the margins, bases not overlapping, tapering from near the base to the subulate apices, 0–1(3)-veined, veins inconspicuous at midlength; calluses hairy; lemmas 7–12 mm, usually conspicuously villous or velutinous, occasionally glabrate, hairs 0.7–2.5 mm, awned, awns 2–4 mm; anthers 3.5–10 mm, dehiscent. 2n = 28, 56.

Leymus innovatus is a North American species that grows in open woods and forests, riverbanks, open prairies, and rocky soils, and often in sandy, gravelly, or silty soils, primarily from northern Alaska to Hudson Bay, and south into the Black Hills region of Wyoming and South Dakota. Morphologically, the two subspecies show some overlap. Bowden recognized them in part because of their difference in ploidy level.

1.  Spikes 8–16 cm long, 8–15 mm wide; lemma hairs 0.7–2.5 mm long      subsp. innovatus

1.  Spikes 3–8 cm long, 15–20 mm wide; lemma hairs 1.5–2.5 mm long      subsp. velutinus

Leymus innovatus (Beal) Pilg. var. innovatus

Spikes 8–16 cm long, 8–15 mm wide. Lemma hairs 0.7–2.5 mm. 2n = 28.

Leymus innovatus subsp. innovatus is the more widespread of the two subspecies, extending across North America from the southern Yukon Territory to Ontario, south in the Rocky Mountains to northern Montana, and, as a disjunct, to the Black Hills region of Wyoming and South Dakota. Closer study is needed to determine its range more exactly.

Leymus innovatus subsp. velutinus (Bowden) Tzvelev

Spikes 3–8 cm long, 15–20 mm wide. Lemma hairs 1.5–2.5 mm. 2n = 56.

Leymus innovatus subsp. velutinus is the more northern of the two subspecies, growing in Alaska, the Yukon Territory, and the western Northwest Territories.

16.  Leymus flavescens (Scribn. & J.G. Sm.) Pilg.

Yellow Wildrye

Plants sometimes cespitose, strongly rhizomatous. Culms 40–120 cm tall, 2–4 mm thick, pubescent beneath the nodes. Leaves exceeded by the spikes; sheaths glabrous; auricles absent, sometimes with a few hairs in the auricular position; ligules 0.3–1.5 mm; blades 3–4 mm wide, usually involute, adaxial surfaces scabrous, sometimes with scattered hairs, hairs to 1 mm, with about 15, closely spaced, subequal, mostly prominently ribbed veins. Spikes 10–20 cm long, 12–20 mm thick, with 12–20 nodes and 2 spikelets per node; internodes 7–10 mm, densely hairy. Spikelets 13.5–25 mm, with 4–9 florets. Glumes 8.5–16 mm long, 0.5–2.5 mm wide, stiff, keeled distally, the central portion thicker than the margins, tapering from below midlength to the subulate apices, hairy, 0–1(3)-veined, veins inconspicuous at midlength; lower glumes 8.5–13.5 mm; upper glumes 10–16 mm; calluses poorly developed; lemmas 10.5–15 mm, densely villous, hairs 2–3 mm, apices unawned or awned, awns to 2 mm; anthers 4.5–7 mm, dehiscent. 2n = 28.

Leymus flavescens grows on sand dunes and open sandy flats, and ditch- and roadbanks, primarily in the Snake and Columbia river valleys. The central Washington population is growing on a road cut; it seems to be well established there.

Plants identified as Elymus arenicolus Scribn. & J.G. Sm. have less densely pubescent lemmas than other specimens. Leckenby, the collector of the type specimen, noted that they grew on sand or sand drifts along the Columbia River, but could not withstand flooding. He could find no seed. Such specimens are included here, but they may represent hybrids between L. flavescens and L. triticoides.

17.  Leymus californicus (Bol. ex Thurb.) Barkworth

California Bottlebrush

Plants loosely cespitose, rhizomatous. Culms 70–200 cm, erect, solitary. Leaves exceeded by the spikes; sheaths with stiff, 1–3 mm hairs; auricles 1–6 mm; ligules 1–5 mm; blades 6–28 mm wide, lax, flat, scabrous, glabrous, or thinly pilose above. Spikes 10–30 cm long, 2–5 cm wide, erect to nodding, lax, nodes with 2–4(5) spikelets, the basal spikelets often on 1–3 mm pedicels; internodes 7–11(15) mm. Spikelets 12–17 mm, appressed to spreading, with 2–5 florets. Glumes absent or shorter than 1 mm; lemmas 10–15 mm, sparsely scabrous to appressed hispid, awned, awns 16–33 mm, straight; anthers 6–8 mm, dehiscent. 2n = 56.

Leymus californicus is endemic to coniferous forests near the coast in western California, from Sonoma to Santa Cruz counties, at elevations from near sea level to 300 m. It used to be included in Hystrix Moench, a genus that was described as lacking glumes. The type species of Hystrix has since been shown to be more closely related to species of Elymus than to other species placed in Hystrix which, with the exception of L. californicus, are native to eastern Asia. Transfer of L. californicus, and some of the other species formerly placed in Hystrix, to Leymus is supported by molecular data (Jensen and Wang 1997; Mason-Gamer 2001). The situation with respect to L. californicus illustrates the danger of circumscribing a taxon by its lack of a character. In this case, it appears that reduction in the glumes has taken place within both Elymus and Leymus.

Leymus californicus is unusual among the other species of Leymus in the contiguous United States in growing in a forested habitat, but L. innovatus also grows in forests, and some of the Chinese species that have traditionally been placed in Hystrix are also reported to grow in forest habitats but recently transferred to Leymus (Yen et al. 2009) . Indeed, these similarities, plus its restriction to the vicinity of San Francisco, suggest the possibility that L. californicus is an introduced Chinese species.