A tall perennial up to 120cm tall, forming a wide clump of stems bearing dark green ovate leaves and loose spikes of vivid cobalt blue flowers, contrasting with black calyx, and opening in mid-summer and autumn.
Best grown in full sun, in well-drained soil with shelter from cold winds. Maintain low humidity for plants overwintered indoors in a greenhouse. Under glass grow in well-drained , peat-free potting compost in full light with shade from hot sun.