Perennial herb; stems creeping and rooting at nodes; internodes with retrorse bifarious hairs. Petioles 3-15 mm long, prominent and ± retrorsely puberulent. Lamina 4-32 × 3-30 mm, ± triangular, strongly and irregularly dentate or dentate-serrate, hairy beneath, particularly on veins, glabrous or, less commonly, puberulent above; base truncate to subcordate; apex obtuse to subacute. Racemes axillary, opposite, with (2)-5- c. 20 fls; peduncles and pedicels slender, very variable in length, retrorsely puberulent. Bracts small, much < pedicels. Calyx 3-5 mm long; lobes oblong or elliptic-obovate, ciliate, somewhat puberulent or glabrous, obtuse and mucronate. Corolla 6-7 mm diam., not opening widely, blue or pale blue. Capsule 3-4 mm wide, obovoid, glabrous, ± emarginate. Seed broadly ellipsoid-oblong, smooth, strongly flattened.