Mary E. Barkworth
Plants perennial; sometimes cespitose, often rhizomatous. Culms 10350 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 18 spikelets per node, sometimes panicles with (2)335 spikelets associated with each rachis node; rachises with scabrous or ciliate edges; internodes 3.512(15) mm. Spikelets 1/23 3/4 times the length of the rachis internodes, usually sessile, sometimes pedicellate, pedicels to 5 mm, appressed to ascending, with 212 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, 03(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 57-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 1633 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, 2.510 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):1320; Barkworth, M.E. and R.J. Atkins. 1984. Leymus Hochst. (Gramineae: Triticeae) in North America: Taxonomy and distribution. Amer. J. Bot. 71:609625; Bowden, W.M. 1957. Cytotaxonomy of section Psammelymus of the genus Elymus. Canad. J. Bot. 35:951993; Bowden, W.M. 1959. Chromosome numbers and taxonomic notes on northern grasses: I. Tribe Triticeae. Canad. J. Bot. 37:11431151; 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. 160:371376; 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. 158:872877; Mason-Gamer, R.J. 2001. Origin of North American Elymus (Poaceae:Triticeae) allotetraploids based on granule-bound starch synthase gene sequences. Syst. Bot. 26:757768; 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. 300306 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 37:231235; 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 49:511519; 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. 78:871884.
1. Glumes absent or shorter than 1 mm; lemmas awned, awns 1633 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 24 branches to 6 cm long at the proximal nodes; culms 115350 cm tall 10. L condensatus
6. Inflorescences usually without branches, sterile hybrids sometimes with branches to 3 cm long; culms 10270 cm tall.
7. Lemmas densely hairy, hairs 0.73 mm long, occasionally glabrate.
8. Lemmas awned, awns 24 mm long; lemma hairs 0.72.5 mm long............. 15. L innovatus
8. Lemmas unawned or the awns to 2 mm long; lemma hairs 23 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 1030(60) cm tall; spikes 28 cm long, with 12 spikelets per node; plants of California coastal bluffs.............................. 5. L. pacificus
9. Leaves exceeded by the spikes; culms 35270 cm tall; spikes 335 cm long, with 18 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 27 spikelets per node; blades 312 mm wide; culms (70)100270 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 16 mm wide; culms 35140 cm tall.
12. Blades with 59 adaxial veins; lemma awns to 2.5 mm long........... 13. L salina
12. Blades with (9)1117 adaxial veins; lemma awns 1.37 mm long............. 14. L ambiguus
10. Plants rhizomatous, culms solitary or a few together.
13. Culms 13 mm thick; glumes 416 mm long.
14. Spikes with 1 spikelet at all or most nodes, sometimes with 2 at a few nodes; lemma awns 2.36.5 mm long; culms 3555 cm tall..................... 6. L simplex
14. Spikes with 2+ spikelets at most nodes; lemma awns to 3 mm long; culms 45125 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 2.512 mm thick; glumes 1030 mm long.
16. Spikelets 38 per node; lemmas hairy proximally, glabrous distally........... 1. L. racemosus
16. Spikelets 23 per node; lemmas glabrous or hairy their whole length.
17. Anthers 69 mm long; blades 311 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 35 mm long; blades 57 mm wide; glumes glabrous, sometimes scabrous........................................................................... 9. L. angustus
Plants not or only weakly cespitose, strongly rhizomatous. often glaucous. Culms 50100 cm tall, 812 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 1.52.5 mm; blades 2040 cm long, 820 mm wide. Spikes 1535 cm long, 1020 mm wide, dense, with 38 spikelets per node; internodes 811 mm, hairy, hairs on the surfaces to 1 mm, on the edges to 1.5 mm. Spikelets 1225 mm, sessile, with 46 florets. Glumes 1225 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 1520 mm, pubescent proximally, glabrous distally, tapering to an awn, awns 1.52.5 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.
European Dunegrass, Ιlyme des Sables dEurope
Plants weakly cespitose, rhizomatous, strongly glaucous. Culms 50150 cm tall, (2)36 mm thick, usually glabrous throughout, occasionally pubescent distally to 5 mm below the spike. Leaves exceeded by the spikes; ligules 0.32.5 mm; blades 311 mm wide, with 1540 adaxial veins. Spikes 1235 cm long, 1525 mm wide, usually with 2 spikelets per node; internodes 812 mm, surfaces glabrous, edges ciliate. Spikelets 1230 mm, with 25 florets. Glumes 1230 mm long, 23.5 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 1225 mm, densely villous, hairs 0.30.7 mm, 57-veined, acute, occasionally awned, awns to 3 mm; anthers 69 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.
American Dunegrass, Sea Lymegrass, Ιlyme des Sables dAmerique, Seigle de Mer
Plants not cespitose, strongly rhizomatous, occasionally slightly glaucous. Culms 12170 cm tall, 36 mm thick, usually densely pubescent below the spikes for 1040+ mm. Leaves exceeded by the spikes; auricles to 0.7 mm; ligules 0.22.5 mm; blades 1094 cm long, 315 mm wide, adaxial surfaces scabridulous to scabrous, 2040-veined, veins subequal, prominently ribbed, closely spaced. Spikes 534 cm long, 1020 mm wide, with 333 nodes, usually with 2 spikelets per node; internodes 4.59.5 mm, surfaces and edges similar, soft, hairs on the surfaces 0.10.5 mm, on the edges to 0.7 mm. Spikelets 1534 mm, with 36 florets. Glumes 934 mm long, 1.54 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 1120 mm, densely hairy, hairs 0.51 mm, soft, apices acute, unawned; anthers 49 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 1234 cm long, with 1233 nodes; basal blades 515 mm wide; culms 50170 cm tall subsp. mollis
1. Spikes 513(16) cm long, with 314 nodes; basal blades 38 mm wide; culms 1270 cm tall subsp. villosissimus
Leymus mollis (Trin.) Pilg. subsp. mollis
Rhizomes 46 mm thick. Culms (50)70170 cm. Basal blades 2294 cm long, 515 mm wide. Spikes 1234 cm, with 1233 nodes. Glumes 1334 mm long, 34 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 1270 cm. Basal blades 1031 cm long, 38 mm wide. Spikes 513(16) cm, with 314 nodes. Glumes 914(21) mm long, 1.52.5 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.
Plants not cespitose, rhizomatous, green or slightly glaucous. Culms 60122 cm tall, 23.5 mm thick, sparsely to densely pubescent below the spike. Leaves exceeded by the spikes; auricles to 1 mm; ligules 0.41.2 mm; blades to 9 mm wide, veins promimently ribbed, subequal, closely spaced. Spikes 732 cm long, 711 mm wide, sometimes glaucous, often purplish or green with traces of purple, with 12 spikelets per node; internodes 812 mm, surfaces hairy distally, hairs 0.10.3 mm, edges ciliate, hairs to 1 mm, coarser than the surficial hairs. Spikelets 1520 mm, with 26 florets. Glumes 928 mm long, 1.54 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 810 mm, usually completely glabrous, margins and apices sometimes pubescent, apices tapering to an awn, awns to 4 mm; anthers 3.37.3 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.
Plants not cespitose, strongly rhizomatous. Culms 1030(60) cm tall, 12 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 0.20.3 mm, truncate, erose; blades 1030 cm long, 24 mm wide, abaxial surfaces glabrous, adaxial surfaces scabrous, veins about 15, subequal, prominently ribbed. Spikes 28 cm long, 712 mm wide, with 12 spikelets per node; internodes 3.54 mm, surfaces glabrous and smooth, edges weakly scabrous distally. Spikelets 1215 mm, with 46 florets. Glumes subequal, (5)715 mm long, 0.52.5 mm wide, narrowly lanceolate, tapering from near the base, stiff, keeled, the central portion thicker than the margins, bases mostly glabrous, margins ciliate, 13(5)-veined, veins inconspicuous at midlength; calluses scarcely developed, glabrous; lemmas 711 mm, glabrous, smooth, apices acute to awn-tipped, awns to 0.8 mm; anthers 34 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.
Plants not cespitose, strongly rhizomatous, often glaucous. Culms 3575 cm tall, 12.5 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 0.30.5 mm, truncate, erose; blades 429 cm long, 12(5) mm wide, flat, becoming involute when dry, stiff, adaxial surfaces scabrous, with scattered hairs to 2 mm, veins 711, subequal, prominently ribbed. Spikes 1.525 cm long, 410 mm wide, with 1 spikelet per node at midspike, sometimes with 2 at the lower nodes; internodes 712 mm, surfaces glabrous or strigillose, edges ciliate, cilia to 1 mm. Spikelets 1625 mm, pedicellate, pedicels 12(5) mm, with 312 florets. Glumes subequal, 812 mm long, 0.51.5 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, 01(3)-veined, veins inconspicuous at midlength; lemmas 712 mm, glabrous, awned, awns 2.36.5(12) mm; anthers 3.74.5 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 5575 cm tall; racemes 1025 cm long; internodes 1012 mm var. luxurians
1. Culms 3555 cm tall; racemes 1.513 cm long; internodes 79 mm var. simplex
Leymus simplex var. luxurians (Scribn. & T.A. Williams) Beetle
Culms 5575 cm tall, 22.5 mm thick. Spikes 1025 cm long; internodes 1012 mm. Spikelets 2025 mm, with 612 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 3555 cm tall, 12 mm thick. Spikes 1.513 cm long; internodes 79 mm. Spikelets 1622 mm, with 36 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.
Plants not cespitose, strongly rhizomatous. Culms 45125 cm tall, 1.83 mm thick, solitary or a few together. Leaves exceeded by the spikes, often basally concentrated; sheaths glabrous or hairy, hairs 0.51 mm; auricles to 1 mm; ligules 0.21.3 mm, truncate, erose; blades 1035 cm long, 3.510 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 1127, closely spaced, subequal, prominently ribbed. Spikes 520 cm long, 515 mm wide, with 2 spikelets at midspike, sometimes 1 or 3 at other nodes; internodes 511.5 mm, usually mostly smooth and glabrous, sometimes strigillose distally, edges ciliate, cilia to 0.4 mm. Spikelets 1022 mm, with 37 florets. Glumes 516 mm long, 0.51.2 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 512 mm, usually glabrous, occasionally sparsely hairy, hairs to 0.3 mm, apices acute, usually awned, awns to 3 mm; anthers 36 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.
Plants somewhat cespitose, rhizomatous. Culms 5080 cm tall, 1.53 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 12 mm; blades 38 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 57, not prominently ribbed. Spikes 514 cm long, 613 mm wide, with 24(6) spikelets per node; internodes 46 mm, glabrous or strigillose, hairs about 0.1 mm, edges ciliate, cilia to 0.4 mm. Spikelets 815 mm, with 26 florets. Glumes 410 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 59 mm, mostly glabrous and smooth, scabrous distally, apices tapering to an awn, awns 23 mm, scabrous; anthers about 34 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.
Plants somewhat cespitose, rhizomatous. Culms 60120 cm tall, 2.57 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 0.51 mm, rounded to obtuse, sometimes erose; blades 1520 cm long, 57 mm wide, glaucous, stiff, involute, abaxial surfaces glabrous, scabridulous, or hairy, adaxial surfaces scabrous, with 717 closely spaced subequal veins. Spikes 1025 cm long, 710 mm wide, with 2(3) spikelets per node; internodes 810 mm, surfaces strigillose, hairs to 0.3 mm, edges ciliate, cilia to 1 mm. Spikelets 1019 mm, with 23 florets. Glumes 1013 mm long, 0.52.5 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 813 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 34 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.
Plants cespitose, weakly rhizomatous. Culms 115350 cm tall, 610 mm thick, usually several to many together. Leaves exceeded by the inflorescences; auricles absent; ligules 0.76 mm on the basal leaves, 47.5 mm on the flag leaves; blades 1028 mm wide, abaxial surfaces glabrous, smooth, adaxial surfaces scabridulous, veins numerous, subequal or unequal. Inflorescences panicles, 1744 cm long, 2060 mm wide, lower nodes with 26 branches, branches to 8 cm, ascending, with 535 spikelets, upper nodes with pedicellate and sessile spikelets; internodes 3.510 mm, glabrous. Spikelets 925 mm, usually pedicellate, pedicels 0.82 mm, with 37 florets. Glumes 616 mm long, 0.52.5 mm wide, narrowly lanceolate, stiff, keeled, the central portion thicker than the margins, glabrous, smooth proximally, scabrous distally, 01(3)-veined, veins inconspicuous at midlength, apices tapering almost imperceptibly into an awn, awns subequal to the glume body; lemmas 714 mm, usually glabrous, apices acute, sometimes awned, awns to 4 mm; anthers 3.57 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 01525 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.
Plants cespitose, rhizomatous. Culms 65210 cm tall, 35 mm thick. Leaves exceeded by the inflorescences; auricles absent; ligules 0.52 mm, truncate, erose; blades 615 mm wide, both surfaces glabrous, adaxial surfaces with numerous closely spaced, unequal veins. Inflorescences 1535 cm long, 925 mm wide, usually spikes, with 26 spikelets per node, occasionally some nodes with 12 branches, branches to 60 mm, strongly ascending; internodes 810 mm, usually glabrous, sometimes scabrous. Spikelets 1725 mm, pedicellate, pedicels 0.52(5) mm, with 69 florets. Glumes 925 mm long, differing in length by 14 mm, usually exceeding the lowest lemmas, 0.52.5 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 812 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.
Great Basin Wildrye
Plants strongly cespitose, weakly rhizomatous, usually bright green, not glaucous. Culms 70270 cm tall, 25 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 1.58 mm; blades 1545 cm long, 312 mm wide, strongly involute to flat, abaxial surfaces glabrous, adaxial surfaces scabrous, 1125-veined, veins subequal, prominently ribbed. Spikes 1029 cm long, 817 mm wide, with 1428 nodes and 27 spikelets per node; internodes 49 mm. Spikelets 925 mm, with 37 florets. Glumes 818 mm long, 0.52.5 mm wide, subulate distally, stiff, keeled, the central portion thicker than the margins, tapering from below midlength, smooth or scabrous, 01(3)-veined, veins inconspicuous at midlength; lemmas 6.512 mm, glabrous or hairy, hairs 0.10.3 mm, apices acute or awned, awns to 3 mm; anthers 47 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.
Plants cespitose, sometimes weakly rhizomatous. Culms 35140 cm tall, 1.53 mm thick, several together. Leaves exceeded by the spikes; auricles to 1 mm; ligules 0.11 mm, truncate; blades 15 mm wide, flat to strongly involute, adaxial surfaces glabrous or sparsely to densely hirsute, with 59 prominently ribbed, subequal veins. Spikes 414 cm long, 411 mm wide, nodes below midspike with 12(3) spikelets, distal nodes with 1 spikelet; internodes 3.59 mm, surfaces glabrous, edges scabrous or strigillose. Spikelets 921 mm, pedicellate, pedicels to 1 mm, with 36 florets. Glumes unequal to subequal, to 12.5 mm long, 0.53.2 mm wide, subulate, stiff, keeled, the central portion thicker than the margins, tapering from below midlength, 01(3)-veined, veins inconspicuous at midlength; lower glumes 012 mm; upper glumes 3.512.5 mm; lemmas 712.5 mm, usually glabrous, sometimes sparsely strigillose, unawned or awned, awns to 2.5 mm; anthers 2.57.5 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
Culms 3590 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, 23 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
Culms 39102 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
Culms 60140 cm. Basal sheaths conspicuously hairy; blades open to involute, abaxial surfaces conspicuously hairy, adaxial surfaces evenly strigillose to strigose. Spikes with 12 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.
Plants loosely cespitose, occasionally rhizomatous. Culms 60110 cm tall, 11.5 mm thick, many together. Leaves exceeded by the spikes; sheaths glabrous or sparsely pubescent; auricles to 1.1 mm; ligules 0.21.2 mm, truncate; blades 2.56 mm wide, flat, adaxial surfaces scabridulous, glabrous, veins (9)1117, unequal, not crowded. Spikes 817 cm long, 510 mm wide, erect, with 2 spikelets at most nodes; internodes 411 mm, surfaces hairy distally, hairs 0.20.8 mm, edges ciliate. Spikelets 1223 mm, with 27 florets. Glumes unequal, 0.52.5 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, 01(3)-veined, veins inconspicuous at midlength; lower glumes 29.5 mm; upper glumes 614 mm; calluses with hairs, hairs about 0.2 mm; lemmas 814.5 mm, glabrous or sparsely strigose, awned, awns 1.37 mm; anthers 3.57 mm, dehiscent. 2n = 28.
Leymus ambiguus grows on steep, often boulder-strewn hillsides at scattered locations in Colorado and New Mexico.
Downy Ryegrass, Boreal Wildrye
Plants sometimes cespitose, strongly rhizomatous. Culms 18105 cm tall, 23 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 0.10.5 mm; blades 26 mm wide, involute, abaxial surfaces scabridulous or smooth, adaxial surfaces scabrous, occasionally with scattered hairs to 1.5 mm, veins unequal, not crowded. Spikes 316 cm long, 820 mm thick, erect, usually well exserted, with 23 spikelets per node; internodes 46 mm, hairy throughout, edges with hairs to 2.5 mm. Spikelets 1018 mm, with 37 florets. Glumes often unequal, 2.512 mm long, 0.51 mm wide, hairy, stiff, keeled, the central portion thicker than the margins, bases not overlapping, tapering from near the base to the subulate apices, 01(3)-veined, veins inconspicuous at midlength; calluses hairy; lemmas 712 mm, usually conspicuously villous or velutinous, occasionally glabrate, hairs 0.72.5 mm, awned, awns 24 mm; anthers 3.510 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 816 cm long, 815 mm wide; lemma hairs 0.72.5 mm long subsp. innovatus
1. Spikes 38 cm long, 1520 mm wide; lemma hairs 1.52.5 mm long subsp. velutinus
Leymus innovatus (Beal) Pilg. var. innovatus
Spikes 816 cm long, 815 mm wide. Lemma hairs 0.72.5 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 38 cm long, 1520 mm wide. Lemma hairs 1.52.5 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.
Plants sometimes cespitose, strongly rhizomatous. Culms 40120 cm tall, 24 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 0.31.5 mm; blades 34 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 1020 cm long, 1220 mm thick, with 1220 nodes and 2 spikelets per node; internodes 710 mm, densely hairy. Spikelets 13.525 mm, with 49 florets. Glumes 8.516 mm long, 0.52.5 mm wide, stiff, keeled distally, the central portion thicker than the margins, tapering from below midlength to the subulate apices, hairy, 01(3)-veined, veins inconspicuous at midlength; lower glumes 8.513.5 mm; upper glumes 1016 mm; calluses poorly developed; lemmas 10.515 mm, densely villous, hairs 23 mm, apices unawned or awned, awns to 2 mm; anthers 4.57 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.
Plants loosely cespitose, rhizomatous. Culms 70200 cm, erect, solitary. Leaves exceeded by the spikes; sheaths with stiff, 13 mm hairs; auricles 16 mm; ligules 15 mm; blades 628 mm wide, lax, flat, scabrous, glabrous, or thinly pilose above. Spikes 1030 cm long, 25 cm wide, erect to nodding, lax, nodes with 24(5) spikelets, the basal spikelets often on 13 mm pedicels; internodes 711(15) mm. Spikelets 1217 mm, appressed to spreading, with 25 florets. Glumes absent or shorter than 1 mm; lemmas 1015 mm, sparsely scabrous to appressed hispid, awned, awns 1633 mm, straight; anthers 68 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.