Black Adder blooms dark purple-black buds that open into striking violet-blue flowers. It has an upright, clump-forming growth habit, and its foliage releases a pleasant licorice scent.

Grows best in full sun and an average to dry, well-drained soil. If desired, pinch main stems in June just before the buds form, to keep the plant compact. After flowering, remove old flowers to promote a second flowering. No serious pest or disease problems.