fire reedgrass

Calamagrostis koelerioides is a rhizomatous perennial grass of cespitose habit. The stout rhizomes are 2–6 cm (0.79–2.36 in) long and 2–4 mm (0.079–0.157 in) thick. The stems are 60–100 cm (24–39 in) long with 3 to 5 nodes. The sheaths and collars are glabrous and usually scabrous, or rarely smooth. The ligule is membranous and 3–7 mm (0.12–0.28 in) long. The leaf blade is 3–7 mm (0.12–0.28 in) wide and is flat or inrolled, and may be scabrous or smooth.

The inflorescence is 5–16 cm (2.0–6.3 in) tall and generally dense and erect to slightly nodding in habit, and with a straw to pale green to pale purple color. The inflorescence branches are generally less than 3 cm (1.2 in) long and appressed, bearing spikelets to their base. The glumes are scabrous, slightly keeled and 4–6 mm (0.16–0.24 in) long, with callus hairs <2 mm (0.079 in) long. The lemma is 4–5 mm (0.16–0.20 in) long, usually 0.5–1.5 mm (0.020–0.059 in) shorter than the glumes, with a small twisted awn 4–5.5 mm (0.16–0.22 in) long which equals or slightly exceeds the length of the glume tips. This species generally flowers from June to August.

Calamagrostis koelerioides is native to the western United States. It shares a partial sympatric distribution with its close relatives C. foliosa and C. ophitidis in Northern California and the California Coast Ranges, but extends further north to the states of Washington, Idaho, Montana, and Wyoming. It is also found further south in the Peninsular Ranges of Southern California. Ira Loren Wiggins reported C. koelerioides (as C. densa) for northern Baja California, but there are no recorded specimens that verify his claim.