Family: Asteraceae
Common Name: Perennial Aster, Michaelmas Daisy

Native to the northern hemisphere, this large genus comprises over 250 species of mostly herbaceous perennials. The Greek aster meaning 'a star', refers to the shape of the flower. The annual aster is Callistephus chinensis, or China aster, and botanically is not an aster at all. Most true asters have leafy clumps at ground level from which emerge flower stems up to 1.5 m (5 ft) high. Clusters of showy, daisy-like flowers are produced from late summer to autumn in colours of blue, violet, purple, mauve, pink, red or white, with a central disc of yellow or black. Asters make excellent cut flowers and will last well if the water is changed frequently.

Species

A. amellus, Italian aster, is a compact plant growing to 60 cm (24 in). It has large flowers in a range of colours from pale pink to shades of blue, with a distinctive golden disc in the center. There are several named varieties. All flower during late summer and autumn.

A. novae-angliae, New England aster, is from eastern North America. This species has downy stems and narrow, gray-green, stem-clasping leaves, and grows to 2 m (6 ft). The large flowers come in pink, red or blue. There are several modern cultivars. All flower in late summer and autumn. A. novi-belgii, also from eastern North America, is the most commonly grown. Many cultivars are available, mainly from perennial plant specialists. They grow to between 50 cm (20 in) and 1.5 m (5 ft). The slender stems branch near the top, the leaves are narrow, smooth and stem-clasping, and the flowers appear in clusters of 20 to 30 in white, pink, mauve, blue, purple or red, with golden yellow or reddish discs. All flower profusely from late summer and autumn. The dwarf hybrids are very pretty, with a similar colour range to that of A. novi-belgii. The flowers bloom from late summer and autumn. The dwarfs grow to 15-30 cm (6-12 in) in height and suit front row or rock garden planting. There are numerous cultivars of dwarf aster and all of them are worth growing in gardens. Garden centers specializing in perennials should hai'e a good range of cultivars of varying heights and colours.

Cultivation

Plant in an open, sunny position in well-drained soil, enriched with organic fertilizer, and dressed with complete fertilizer at 40 g per square metre (1½ oz per square yard). Animal manure or compost should be applied generously to the beds as a mulch. Set new plants, with their crowns at soil level, about 45 cm (18 in) apart (20 cm or 8 in for the dwarf hybrids) in clumps of five to seven of each variety. Water well in spring and summer, adding 40 g (1½ oz) of complete fertilizer per plant in late spring and summer to ensure healthy growth and large flowers. When the flowers have faded on the plant, cut hack the long stems to ground level and tidy the clumps. Sometimes flowers will be produced in smaller numbers in late autumn. A generous mulch around the old clump in late winter helps these plants to conserve moisture. Propagate by division of the established clumps in late winter or early spring. A single, well-grown crown can produce at least 15 new plants, with sound crowns and roots, in one year.

Climate

The following species will grow in zone 2, except for A. amellus which requires zone 5.