Erect, sparingly branched, semi-aquatic, perennial herb up to 45 cm tall; all parts except corolla densely covered with a viscid, glabrescent, often mealy, indumentum of sessile, golden, globose glands, and sparse glandular hairs; indumentum most conspicuous on leaves, bracteoles, sepals, and pedicels. Stems lime-green or red-purple, submerged parts rooting freely. Leaves sessile, triple-nerved, 8—18 × 3—10 mm, lime-green, ovate to lanceolate; margins widely toothed, leaf base amplexicaule. Flowers solitary in leaf axils, sweetly scented. Pedicels 10—12(—16) mm long, 1-2 per leaf axil. Bracteoles 1—2(—3) mm long, linear-falcate. Sepals 5, free, erect, narrowly lanceolate, 4—5 mm long. Corolla white flushed yellow, with 12—14 longitudinal purple stripes; tube 6 mm long, narrow, inner surface densely covered in white silky hairs; lobes 5, projecting forward, 1 mm long, upper one occasionally shallowly 2-lobed. Anthers white, ovoid, 0.5 mm long; pollen mealy, white; filaments yellow, glabrous, 2—3 mm long; staminodes 2 or 0, when present filiform and minute. Style caducous, 1.8-2.1 mm long. Capsule 3-5 mm long, broadovoid, often slightly exceeding the calyx, septicidal to base. Seeds 0.3-0.5 mm long, usually elliptic or elliptic-oblong with rounded ends; testa dull, orangebrown; reticulations distinct, deep and with slightly thickened walls, these mucilaginous when fresh. FL Nov—Jan, FT Dec—Mar.