13.12 ×ELYHORDEUM Mansf. ex Tsitsin & K.A. Petrova

Mary E. Barkworth

Plants perennial; usually cespitose, occasionally shortly rhizomatous. Inflorescences terminal, spikes or spikelike, with 1–3(7) spikelets per node, lateral spikelets usually shortly pedicellate, central spikelets sessile (or nearly so); disarticulation tardy, at the rachis nodes and beneath the florets. Spikelets with 1–4 florets. Glumes subulate to narrowly lanceolate, usually awned; lemmas usually awned; anthers sterile. Caryopses rarely formed.

×Elyhordeum is the name given to hybrids between Elymus and Hordeum. These hybrids are fairly common. All appear to be sterile, i.e., they do not produce good pollen or set seed. The descriptions should be treated with reservation because, in some instances, only type specimens have been examined. For that reason, no key is provided. Only named hybrids are described and illustrated.

Interspecific hybrids between Elymus elymoides or Elymus multisetus and other species of Elymus resemble the ×Elyhordeum hybrids in having tardily disarticulating, spikelike inflorescences and awned glumes and lemmas, but are more likely to have solitary spikelets, even at the lowest node. Distinguishing between them and ´Elyhordeum hybrids, without knowledge of other species of Triticeae at a site, is challenging.

Inflorescence measurements do not include the awns.

SELECTED REFERENCES Bowden, W.M. 1958. Natural and artificial ×Elymordeum hybrids. Canad. J. Bot. 36:101–123; Bowden, W.M. 1960. Typification of Elymus macounii Vasey. Bull. Torrey Bot. Club. 87:205–208; Jordal, L.K. 1951. A floristic and phytogeographic survey of the southern slopes of the Brooks Range, Alaska. Ph.D. dissertation, University of Michigan, Ann Arbor, Michigan, U.S.A. 411 pp.; Mitchell, W.W. and H.J. Hodgson. 1965. A new ×Agrohordeum from Alaska. Bull. Torrey Bot. Club 92:403–407.

1. ×Elyhordeum dakotense (Bowden) Bowden

Culms 55–80 cm. Ligules about 0.2 mm, truncate; blades 1.5–2 mm wide. Spikes 7–10 cm long, 5–8 mm wide, nodding, with 2(3) spikelets per node. Spikelets with 2–4 florets. Glumes 20–50 mm including the awns, bases indurate; lemmas pubescent, awned, awns similar in length to those of the glumes; anthers not developed. 2n = unknown.

×Elyhordeum dakotense refers to hybrids between Elymus canadensis and Hordeum jubatum. They are known only from Brookings, South Dakota.

2. ×Elyhordeum macounii (Vasey) Barkworth & D.R. Dewey

Culms 50–100 cm. Sheaths usually glabrous; ligules truncate; blades 9–16 cm long, 2–5 mm wide, stiff, ascending, scabrous. Spikes 4–13 cm long, about 5 mm wide, erect, lower nodes with 1–2 spikelets, upper nodes with 1 spikelet, the spikelets imbricate. Spikelets with 1–3 florets, those at the lower nodes frequently with 3 glumes. Glumes 6–9 mm, not indurate at the base, awned, awns as long as or longer than the glume bodies; lemmas 6–11 mm, oblong-lanceolate, glabrous or scabrous, sometimes scabrous distally, awned, awns 10–20 mm. 2n = 28.

×Elyhordeum macounii consists of hybrids between Elymus trachycaulus and Hordeum jubatum. It is quite common in western and central North America. Backcrosses to E. trachycaulus may have non-disarticulating rachises; they are likely to be identified as E. trachycaulus, falling between subsp. trachycaulus and subsp. subsecundus. Artificial, partially fertile octoploids were distributed to natural and experimental areas in several western states prior to 1960 (Bowden 1960); it is not known whether they have persisted.

3. ×Elyhordeum pilosilemma (W.W. Mitch. & H.J. Hodgs.) Barkworth

Culms 40–75 cm, erect, glabrous. Sheaths glabrous or pubescent; blades 6–15 cm long, 2–4 mm wide, flat, adaxial surfaces glabrous or hairy. Spikes 6–12 cm long, 5–7 mm wide, including the awns, erect to arching, with 1–2 spikelets per node; internodes 2–5 mm, concealed by the spikelets. Spikelets 7–13 mm, with 2–3 florets and 2–3 glumes. Glumes 10–18 mm, including the awns, not indurate at the base, linear to linear-lanceolate, hispid, 1–3-veined; lemmas 7–10 mm, evenly pilose, hairs about 0.2 mm, awns as long as to slightly longer than the lemma bodies; anthers 1–1.5 mm, indehiscent. 2n = 28.

×Elyhordeum pilosilemma is a hybrid between Elymus macrourus and Hordeum jubatum that occurs in many locations where the two parental species co-occur. It is very similar to ×Elyhordeum jordalii, a hybrid between Elymus macrourus and Hordeum brachyantherum.

4. ×Elyhordeum jordalii (Melderis) Tzvelev

Culms 25–30 cm. Lower sheaths puberulent; blades 2.5–4.5 mm wide, adaxial surfaces slightly scabrous. Spikes 4–12 cm, erect to slightly nodding, usually with 2 spikelets per node. Spikelets 7–12 mm, excluding the awns, with 2–3 florets. Glumes 7–13 mm long, bases about 1 mm wide, not indurate, with a prominent, scabridulous midrib, apices gradually tapering into an awn shorter than 20 mm; lemmas 6–8 mm, shortly pubescent, the pubescence decreasing in density towards the apices, apices awned, awns 5–8 mm; anthers about 1.5 mm, indehiscent. 2n = unknown.

×Elyhordeum jordalii consists of hybrids between Elymus macrourus and Hordeum brachyantherum. It grows in the Brooks Range, Alaska. According to Jordal (1951), it was “only observed near settlements on the lowlands south of the range where it has a weedy habit. Dense tufts near cabins.” It resembles ×Elyhordeum pilosilemma, which differs in having Hordeum jubatum as the Hordeum parent.

5. ×Elyhordeum schaackianum (Bowden) Bowden

Culms about 100 cm. Sheaths glabrous, smooth; ligules about 0.7 mm, truncate; blades 6–10 mm wide, flat, adaxial surfaces sparsely hairy, hairs about 0.8 mm. Inflorescences spikelike, 9–11 cm long, 10–12 mm wide, lax, with (2)3 spikelets per node. Spikelets with 1–2 florets, the second floret, if present, rudimentary, the lateral spikelets shortly pedicellate, the central spikelet sessile or nearly so. Glumes narrow, coarse, unawned or awned, awns to 15 mm; lemmas mostly glabrous, margins shortly hairy distally, apices unawned or awned, awns to 15(20) mm. 2n = 28.

×Elyhordeum schaackianum consists of hybrids between Elymus hirsutus and Hordeum brachyantherum. It is known only from Attu Island, Alaska, and the Queen Charlotte Islands, British Columbia.

6. ×Elyhordeum stebbinsianum (Bowden) Bowden

Culms 60–80 cm. Blades 3–5 mm wide, abaxial surfaces smooth, adaxial surfaces scabridulous. Inflorescences spikelike, 10–16 cm, with 3 spikelets per node; internodes averaging 3.4 mm. Spikelets with 1–3 florets, the lateral spikelets sessile or pedicellate, pedicels to 3 mm. Glumes 0.5–1 mm wide, terminating in a 4–7 mm awn; lemmas glabrous to scabrous, awned, awns 5–11 mm; anthers indehiscent. 2n = unknown.

×Elyhordeum stebbinsianum consists of hybrids between Hordeum brachyantherum and Elymus glaucus. Bowden (1958) reported that they appear to be completely sterile. They have been found at scattered locations in western North America.

7. ×Elyhordeum iowense R.W. Pohl

Culms 40–80 cm, erect. Sheaths hirsute; ligules about 0.3 mm; auricles short, acute; blades 6–8 mm wide, adaxial surfaces shortly velutinous. Inflorescences spikelike, 9–12 cm long, 5–10 mm wide, flexuous, with 3 spikelets per node. Spikelets with 2 florets, the lateral spikelets usually shortly pedicellate, the central spikelet sessile. Glumes about 2.5 cm, not indurate at the base; lemmas about 6–8 mm, puberulent, awns 25–35 mm; anthers 1.6–1.8 mm, indehiscent in the lowest florets of each spikelet. 2n = 28.

×Elyhordeum iowense is a hybrid between Elymus villosus and Hordeum jubatum that has been found at scattered locations in the central plains. It probably occurs elsewhere, but is unlikely to be common, because Elymus villosus usually grows in more shady locations than Hordeum jubatum.

8. ×Elyhordeum arcuatum W.W. Mitch. & H.J. Hodgs.

Culms 40–85 cm. Blades 7–22 cm long, 3–10 mm wide, abaxial surfaces scabrous, adaxial surfaces pilose. Inflorescences spikelike, 6–15 cm, arcuate to nodding, with 3 spikelets per node; central spikelets sessile, with 1–3 florets; lateral spikelets shortly pedicellate, with 0–2 florets. Glumes to 25 mm, awnlike, scabrous; lemmas 9–11 mm, scabrous, awned, awns to 25 mm, arcuate and divergent at maturity; anthers 1–1.4 mm. 2n = 28.

×Elyhordeum arcuatum is probably a hybrid between Elymus sibiricus and Hordeum jubatum (Mitchell and Hodgson 1965). It was described from disturbed sites around Palmer, Alaska, from which it has since been eliminated. No additional reports are known. There is no illustration because the type specimens could not be located.

9. ×Elyhordeum montanense (Scribn. ex Beal) Bowden

Culms 60–100 cm. Sheaths glabrous; blades 5–8 mm wide, flat, lax. Inflorescences spikelike, 8–17 cm, nodding, with 3 spikelets per node. Spikelets with 1–4 florets, the lateral spikelets usually shortly pedicellate, with 1(2) sterile florets, the central spikelet sessile, with 2(3–4) sterile florets, the third and fourth florets rudimentary. Glumes 10–35 mm, including the awns, slightly widened above the base; lowest lemma of central florets about 8 mm, glabrous toward the base, sparsely scabrous distally, awned, awns 15–25 mm, straight to slightly divergent at maturity. 2n = 28.

×Elyhordeum montanense applies to hybrids between Elymus virginicus and Hordeum jubatum. It is often found in disturbed areas where both parental taxa grow. Short-awned specimens may reflect the involvement of Elymus submuticus, rather than Elymus virginicus.

10. ×Elyhordeum californicum (Bowden) Barkworth

Culms 30–40 cm, glabrous throughout or hairy on the lower portion. Sheaths glabrous; auricles to 0.5 mm; ligules 0.4–1.5 mm, rounded; blades to about 15 cm long, 1–2(3) mm wide, abaxial surfaces glabrous or sparsely hairy, adaxial surfaces scabridulous, all veins equally prominent. Inflorescences spikelike, 2.5–5 cm long, 7–10 mm wide excluding the awns, 20–30 mm wide including the awns, straight, nodes with 3 spikelets; internodes 2.2–4 mm, bases about 1/2 as wide as the apices. Spikelets 8–10 mm excluding the awns, 25–28 mm including the awns, with 1–2 florets, the lateral spikelets shortly pedicellate, the central spikelet sessile. Glumes 15–35 mm including the awns, setaceous, straight; lemmas 7–8 mm, smooth throughout or scabrous distally, awned, awns 10–20 mm, straight or slightly divergent at maturity; anthers about 1.5 mm.

×Elyhordeum californicum consists of hybrids between E. elymoides or E. multisetus and Hordeum brachyantherum subsp. brachyantherum. It was described by Bowden (1958) on the basis of specimens collected in California. It seems probable that it will be found at many locations where the two parents grow together.