Herbaceous perennial. Stems up to 120 cm, arising from a woody rhizome, erect, not or little branched, quadrangular, with a short pilose eglandular or finely eglandular indumentum, usually glandular on inflorescence axis, leafy. Leaves 40-80 x 20-40 mm, narrow to broad ovate, green above, paler below, truncate to cordate, ± regularly serrate, acute, eglandular-piose below with numerous sessile oil globules; petiole on lower leaves to 2 cm, less above. Inflorescence of separated verticillasters, lowermost pedunculate in leaf axils, upper ± sessile and approximating. Bracts linear, longer than pedicels to c. 1/3 calyx length. Pedicels to 2.5 mm. Calyx c. 9 mm, almost straight, tubular-obtriangular, densely papillose-glandular and with oil globules; throat slightly oblique; teeth somewhat unequal, broad-triangular lanceolate, longest to c. 3 mm, acute. Corolla 20-25 mm, pale mauve to deep violet blue; tube slightly curved, slender below, exserted, abruptly dilated above; upper lip deeply bilobed, lower lip reflexed or spreading, longer than upper. Nutlets c. 2.1 x 1.5 mm, dark brown, broad obovoid, minutely granular with a small bilobed basal areole (few nutlets seen).