Family: Asteraceae

From Mexico and Central America, these tender annuals and perennials have delicate, fern-like foliage and broad, daisy-like flowers in single or double forms. There are about 12 species in the genus. As some species are quite tall, they make excellent background plants for borders, and also provide cut flowers in a range of interesting colours. Choose freshly opened flowers, scald the bottoms of the stems in boiling water for 15 seconds, then plunge into cold water.

Species

C. atrosanguineus, black cosmos, is a clump-forming perennial, growing to 1 m (3 ft), with a bushy habit, dark, brownish red, summer flowers and a distinctive, chocolate aroma.

C. bipinnatus is an erect, bushy annual, to 1 m (3 ft), producing white, rose or purple flowers in late summer. Popular cultivars of this species include 'Candystripe', 'Sea Shells' and the Sensation Series.

C. sulphureus, yellow cosmos, grows 1 m (3 ft), with pale yellow flowers. There are several cultivars available with flowers in various shades of orange, red or yellow. Some cultivars have semi-double flowers. These all make a dazzling summer display.

Cultivation

In frost-prone climates, sow seed under glass in mid-spring, germinate with bottom heat, and plant out when frosts are over. Alternatively, sow where the plants are to flower in late spring. Cosmos likes a well-drained, yet moisture-retentive soil that is not too rich, and a position in full sun. It is important to remove the dead flower heads regularly as this encourages more flowers to follow. In frost-prone areas, the tubers of C. atrosanguineus should be lifted in autumn and stored in slightly moist peat in a frost-free greenhouse over winter. Propagate from basal cuttings in spring.

Climate

Zone 9 for most species.