3. Muhlenbergia capillaris (Lam.) Trin. var. capillaris (hair grass)

Pl. 151 f–h; Map 613

Plants without rhizomes, forming tufts. Flowering stems 35–100 cm long, erect or ascending, glabrous and shiny between the nodes or sometimes minutely hairy just below the nodes. Leaf sheaths glabrous or somewhat roughened, rounded on the back, the ligule 1.8–8.0 mm long. Leaf blades 15–35 cm long, (1.5–)2.0–4.0 mm wide, flat or with inrolled margins, roughened. Inflorescences relatively loose, open, terminal panicles 15–40 cm long, elliptic to ovate in outline, the base sometimes enclosed by the subtending leaf sheath, the branches loosely ascending to spreading at maturity. Spikelets 2.6–5.0 mm long (excluding the awns), long‑stalked, the stalks mostly several times as long as the spikelets. Glumes about the same length, the body 1.0–2.3 mm long, shorter than the floret, narrowly ovate, strongly overlapping at the base, the margins curved from below the middle and tapered to the sharply pointed (rarely minutely 2‑toothed) tip, the lower glume 1‑nerved and sometimes with an awn 0.5–3.0 mm long, the upper glume 1‑nerved or less commonly 3‑nerved and sometimes with an awn 0.5–5.0 mm long. Lemma with the body 2.6–5.0 mm long, lanceolate, the tip sharply pointed and with an awn 4–20 mm long, minutely hairy at the base, otherwise roughened, especially toward the tip. Anthers 1.2–2.0 mm long. Fruits 2.0–2.8 mm long. August–October.

Scattered in the Ozark and Ozark Border Divisions (southeastern U.S. west to Kansas and Texas, north along the eastern seaboard to Massachusetts; Mexico, Caribbean Islands). Upland prairies, glades, tops of bluffs, savannas, and openings of dry upland forests, often on acidic substrates, sometimes in areas of cherty dolomite; also roadsides.

Morden and Hatch (1989) recognized three varieties of M. capillaris that had been treated as separate species by previous authors (Reeder, 1975). In addition to the widespread var. capillaris, the other two are endemic to the Atlantic and Gulf Coastal Plains. The var. trichopodes (Elliott) Vasey differs from var. capillaris in its relatively long, awnless glumes, and var. filipes (M.A. Curtis) Chapm. ex Beal differs in its glumes with long awns and lemmas with two narrow teeth at the tip. Steyermark (1963) noted that earlier reports of var. trichopodes (as M. expansa) from Missouri were based upon misdetermined specimens of var. capillaris. The spikelets of M. capillaris usually have a distinctive purple coloration.