The perennials of this species flower during the summer, and will flourish in any garden soil. Seeds may be sown in spring, but the best method of increase is by division in spring. The flowers are produced in a variety of colours and grow to a height of 4-ft. A few good species for the amateurs garden are:
C. glaslifolia. Bright yellow. June to August. 2-ft.
C. macrocephala. Bright yellow. July to August. 3-ft.
C. monlana. Blue flowers. May to September. 18-in.
C. ruthenica. Pale yellow. July to September. 4-ft.
G. stricta. Grey foliage with mauve flowers. 4-in. This variety is suitable for growing in the rock garden.