Corolla 5–14 mm. long, white, pale pink, lilac to mauve-pink; adaxial lip broad emarginate; abaxial lip trilobed, lobes broadly ovate; tube with finely clavellate papillae within, glabrous without.
Flowers sessile to sub-sessile, bracteate, in densely flowered spikes, or occasionally solitary-axillary; bracts reduced, leaflike; bracteoles two, c. 3.5 mm. long, linear, glandular-hirsute.
Stems to 50 cm. tall, simple or branched towards apex, aerial part densely white crisped glandular-hirsute, submerged part glabrous.
Calyx 5–6 mm. long, glandular-hirsute, not striate at maturity; lobes 3 mm. long, narrowly lanceolate-acuminate.
Stamens with posterior filaments 2 mm. long, anterior, 3.75–4 mm. long, glabrous.
Capsule about 3 mm. long, compressed ovoid, black.
Amphibious annual.