Perennial tufted herb, 5–80 cm high, branching below inflorescence, glabrous or sometimes sparsely hirsute.
Leaves alternate or opposite, obovate or oblanceolate, becoming linear up the stem, 2–60 mm long, 0.2–10 mm wide, apex obtuse to acute, margins flat or undulate, entire or with small callus teeth, glabrous or sometimes lower leaves sparsely hirsute.
Flowers in cymes. Sepals 1–3 mm long. Corolla usually blue, sometimes white or pink; tube 1–4.5 mm long; lobes 1.5–6 mm long. Style usually 3-fid, usually not constricted.