Plants perennial; densely tufted, not stoloniferous, not rhizom-atous. Basal branching extra-vaginal. Culms 50–120 cm, stout. Sheaths closed for 1/2–3/4 their length, distinctly com-pressed, keels winged, bases of basal sheaths glabrous; ligules 1–2 mm, smooth or sparsely scabrous, apices truncate; blades (4)6–15 mm wide, flat or folded, apices broadly and abruptly prow-shaped. Panicles 10–20 cm, ovoid to pyramidal, open, spikelets numerous, with 3–5 branches per node; branches ascending to spreading, angled, angles densely scabrous. Spikelets 4–9 mm, laterally compressed; florets 3–5; rachilla internodes about 1 mm, scabrous, glabrous. Glumes distinctly keeled, keels scabrous; lower glumes 1–3-veined; calluses glabrous; lemmas 3.5–4.5 mm, narrowly lanceolate, distinctly keeled, scabrous, glabrous throughout, lateral veins prominent, apices acute; palea keels scabrous, glabrous; anthers 1.5–3 mm. 2n = 14.
Poa chaixii was introduced from Europe as an attractive ornamental, and has occasionally escaped. A population in southwestern Quebec has been extirpated.