Annual with fibrous roots; glabrous, glaucous. Stems slender, erect, with few ascending basal branches, 3–12 cm high. Basal leaves rosulate, shortly petiolate, soon withering; upper leaves sessile, linear-lanceolate to linear, 5–15 mm long, 0.7–2 mm wide, acute. Inflorescence lax, few-flowered. Flowers c. 8 mm diam.; pedicels rigidly erect, glabrous, 10–50 mm long; calyx glabrous, sepals lanceolate, acute, with broad, white-scarious margins, 4.5–7 mm long; petals white, two-thirds the length of sepals; styles 4. Capsule equalling or slightly longer than sepals, more or less cylindric, opening by 8 teeth; seeds reddish-brown, finely tuberculate, 0.5–0.7 mm diam. Flowers Aug.–Nov.