Perennial, 1–4 dm from slender rhizomes, glabrous or hispidulous; basal lvs oblanceolate, acute, 1.5–3 cm × 1.5–3 mm; cauline lvs 5–10 pairs, lance-linear, acute, 2–4 cm; fls scattered on pedicels 1–4 cm; cal 12–18 mm, 30–40-nerved; pet-blade red-purple, lavender, or white, 5–10 mm, toothed around the end; fr equaling the cal; 2n=30. Native of Europe, occasionally escaped from cult. mainly in the n. part of our range. May–Aug.