4. Pycnanthemum tenuifolium Schrad. (slender mountain mint)

Pl. 440 g, h; Map 1985

Stems 40–80(–100) cm long, glabrous or rarely sparsely and minutely hairy on the angles. Leaves sessile. Leaf blades 1.5–5.5 cm long, 1.0–5.5 mm wide (those of the largest leaves 1.5–5.5 mm), linear, angled or short-tapered at the base, the margins entire, the surfaces glabrous, green. Inflorescences relatively dense, often appearing relatively flat-topped, only the lowermost branches observable. Bracts dissimilar to the foliage leaves (2.5–4.0 mm long, lanceolate to narrowly ovate, with a thickened midvein and a nearly spinescent tip), not whitened, but grayish green, densely pubescent with short, curled hairs on the surfaces and longer, bristly hairs on the margins and tip. Bractlets 2–3 mm long, mostly lanceolate. Calyces 3.5–5.0 mm long, actinomorphic or nearly so, densely or occasionally sparsely pubescent with short, curled hairs below the lobes, lacking longer bristly hairs on the margins, the lobes all similar in size and shape 1.0–1.5 mm long, triangular, sharply pointed and sometimes with a minute, sharply pointed extension of the midnerve. Corollas 5–7 mm long, white or less commonly pale lavender. Nutlets 0.7–1.0 mm long, usually glabrous. 2n=80. June–September.

Scattered nearly throughout the state (eastern U.S. west to Minnesota, Nebraska, and Texas; Canada). Mesic to dry upland forests, savannas, glades, bottomland prairies, upland prairies, banks of streams and rivers, fens, and ledges and tops of bluffs; also ditches, pastures, old fields, railroads, and roadsides.

Gleason and Cronquist (1991) noted that this species does not produce a strong odor when the foliage is crushed.