Erect perennial 2–60 cm high, much-branched, glabrous. Leaves alternate, linear or narrow-elliptic to -oblanceolate, 2–6 cm long, 1–4 mm wide. Inflorescence many-flowered; bracts 5–10 mm long; pedicels 2–5 mm long. Sepals 2–3 mm long; corolla 9–12 mm long, yellow, spur backwards-directed from tube, 6–12 mm long; upper lip with lobes pointed outwards, lower lip with pilose palate closing mouth, shorter than upper lip, lobes recurved. Capsule c. ovoid, 5–11 mm long; seeds with tuberculate marginal wing. Flowers spring–autumn.