Family: Asteraceae

Whilst these annuals and perennials are mostly of Eurpoean origin, they are now grown worldwide. They are well suited as bedding and border plants, pot plants and background texture plants. Since the flowers are like thistles, it is not surprising that some species have become serious weeds.

Species

C. cyanus, cornflower, zone 6, is an annual, 40-50 cm (16-20 in) tall, which provides very good cut flowers. It has narrow, cottony leaves and the flower heads range in colour from white to blue to rose.

C. dealbata, zone 3, grows to 1 m (3 It), with pinkish purple flowers and silvery white, lobed leaves.

C. macrocephala, zone 3, to 1.5 m (5 ft), makes a good border plant. It has large, yellow, thistle-like flowers, to 10 cm (4 in) in diameter, in summer.

C. montana, zone 3, is among the easiest to grow. It produces deep blue flowers in late spring and summer, and grows to about 50 cm (20 in). Var. alba has white flowers; roses has pink flowers.

C. moschata, (now known as Amberboa moschato), sweet sultan, zone 8, is a bushy annual, with smooth, lobed leaves and fragrant, white, yellow or purple flowers.

Cultivation

These plants like a rich soil and at least half a day's sun. Effective drainage and good air circulation are vital as Centaurea is susceptible to mildew. Propagate annuals from seed sown in spring where they are to flower. Perennials are propagated by division of established clumps in early spring. They do not require much care apart from weeding and perhaps staking for some of the taller kinds.

Climate

There are species for various climatic zones.