Perennial, usually unbranched, with finely hairy, square stems. Flowers in tight clusters toward the ends of stems, often with up to 4 clusters stacked atop one another; beneath each cluster is a whorl of oval, pointed bracts with hairy fringes. Flowers are typical of the mint family, with an upper lip and a 3-lobed lower lip; pale lavender with purple spots. Blooms May-August. Leaves soft, opposite, lanceolate to ovate with only a few soft teeth, usually sessile. All green parts have a mild, pleasant, minty scent. Basal leaves remain green all through the winter.
Similar species: Hairy wood mint (B. hirsuta) is usually branched; its leaves have petioles (leaf stems), many fine teeth, and long, spreading hair. It blooms May-September and grows in cool places, ravines, and wooded slopes statewide. Mints in the genus Monarda (horsemint, wild bergamot, beebalm) look rather similar, too.