Mary E. Barkworth, Julian J.N. Campbell and Bjorn Salomon
Plants cespitose, not rhizomatous. Culms 20–50 cm, prostrate or decumbent and geniculate; nodes 1–2, exposed, glabrous. Leaves basally concentrated; sheaths glabrous; auricles usually present, to 1 mm on the lower leaves; ligules 0.2–0.5 mm, erose; blades 1–5 mm wide, flat, abaxial surfaces smooth, glabrous, adaxial surfaces prominently ridged over the veins, with scattered hairs, hairs to 0.2 mm, veins closely spaced. Spikes 5–15 cm long, 1.5–2.5 cm wide including the awns, 0.7–1.2 cm wide excluding the awns, flexuous, erect to nodding distally, with 1 spikelet at most nodes, occasionally some of the lower nodes with 2 spikelets; internodes 5–15 mm long, 0.2–0.5 mm wide, both surfaces glabrous, edges ciliate, not scabrous. Spikelets 15–20 mm, ascending to divergent, with 3–7 florets, rachillas glabrous; disarticulation above the glumes, beneath each floret. Glumessubequal, 6–9 mm long, 0.7–1 mm wide, lanceolate, glabrous, the bases evidently veined, apices entire, tapering into a 3–10 mm awn; lemmas 12–16 mm, glabrous, sometimes scabridulous, apices bidentate, awned, awns 15–30 mm, arcuately diverging to strongly recurved; paleas subequal to the lemmas, apices about 0.4 mm wide; anthers 2–3.5 mm. 2n = 28.
Elymus sierrae is best known from rocky slopes and ridge tops in the Sierra Nevadas, at 2130–3375 m, and is also found in Washington and Oregon. It resembles E. scribneri , differing in its non-disarticulating rachises, longer rachis internodes, and longer anthers. Hybrids with E. elymoides have glumes with awns 15+ mm long, and some spikelets with narrower glume bases and shorter anthers. Specimens with wide-margined glumes suggest hybridization with E. violaceus .