Plant: perennial, rhizomes thicker and tuber-like near tip; stems erect, 3-8(10) dm, puberulent to short-hairy Leaves: 2.5-7(9) cm, ± sessile, lanceolate to narrowly elliptic, serrate, glabrous to puberulent INFLORESCENCE: cyme, axillary, each head-like, subtended by leaves Flowers: calyx 5-lobed, lobes ± equal, awl-like, acuminate to short-awned; corolla 3-5 mm, slightly > calyx, white, generally 4-lobed, lobes ± unequal; stamens 2, exserted, staminodes 2, minute, club-shaped; style exserted Fruit: Fruit: nutlets 4, 1.5-2 mm, ± compressed; edge corky-thickened; top truncate, sometimes minutely toothed Misc: Moist areas, marshes, streambanks; < 1300 m.; Jun-Oct