'Superba' is a C. glomerata cultivar selected for its outstanding blue, large flower clusters. It grows taller than the species, generally about 20 to 30 inches tall and 12 to 18 inches wide. It has an upright, sort of erect habit and dark green, ovate to arrow-shaped leaves. Flowers are and open bell-shape, and appear in upward facing clusters at the ends of stems. Blooms late spring to mid summer. A lovely cut flower, use in the perennial border.
Grow in full sun to part shade, in well drained, loamy garden soil. Manages with very little water when sheltered from mid day sun. After blooming, you can snip away about a third of the plant, if you'd like a tidier appearance. Deadheading prolongs the blooming season, and as they make a lovely cut flower, snip them off and enjoy inside. Otherwise, cut back in late winter to early spring, as new growth emerges.