Plants without rhizomes, forming tufts. Flowering stems 30–100(–150) cm long, glabrous. Leaf blades 5–40 cm long, 2–6(–8) mm wide, usually flat, roughened or hairy, sometimes with a pair of inconspicuous, minute auricles at the base. Inflorescences 4–15(–25) cm long, erect or nearly so, with the spikelets strongly overlapping on the inflorescence axis, occurring singly (rarely paired) at the nodes, the axis persistent, not breaking into segments at maturity. Spikelets with 3–5(–7) florets, erect or ascending, disarticulating above the glumes and between the florets. Glumes similar in size and appearance (the lower glume slightly shorter than the upper), the body 6–12 mm long, 0.5–1.0 mm wide, linear, 3–5(–7)‑nerved, flattened and straight or nearly so at the base, glabrous or less commonly somewhat roughened, tapered to a sharply pointed or short‑awned (1–5 mm) tip. Lemmas with the body 7–13 mm long, elliptic‑lanceolate, 3‑ or 5‑nerved, glabrous or roughened toward the tip, sometimes hairy along the margins, the tip awnless or with the awn 1–20 mm long, straight. Paleas mostly 7–12 mm long, the tip rounded or truncate. Anthers 1.0–2.0(–2.5) mm long. 2n=28. June–August.

Introduced, scattered, mostly north of the Missouri River (northeastern U.S. south to North Carolina and Illinois; Arizona, New Mexico, Canada). Pastures, cemeteries, and open, disturbed areas.

Attempts to divide this species into varieties have been unsuccessful. A single historical specimen from Barry County has been determined as ¥Elyhordeum macounii (Vasey) Barkworth & D.R. Dewey (Elymus macounii Vasey, ¥Agrohordeum macounii (Vasey) Lepage), which represents a sterile hybrid between E. trachycaulus and Hordeum jubatum L. (Boyle and Holmgren, 1955). This specimen was collected from ledges of limestone bluffs at Eagle Rock and does not appear to represent an introduction. The taxon was excluded from the state’s flora by Steyermark (1963), and other specimens from the area that originally were determined as E. ¥macounii were redetermined by him as E. glaucus. ¥Elyhordeum macounii resembles Elymus trachycaulus but tends to have the spikelets paired at the nodes and lemmas with longer awns. Also, the inflorescence tends to disarticulate at the nodes. Based on the paired spikelets, plants tend to key incorrectly to Elymus glaucus in the key to species above. Aside from its shrunken fruits, the hybrid differs from E. glaucus in its somewhat narrower glumes and the tendency of the inflorescence axis to shatter. This hybrid should be searched for in northern Missouri, where the presumed parents grow together more commonly.