Among garden asters, the types most commonly grown today descend from Aster dumosus, a native of the Eastern United States. Thie wild species ranges from 8 to 16 inches tall, has small lilac-blue flowers and creeping rootstocks that are not overly aggressive. Worthy cultivars include ‘Jenny’ which blooms in late August, and ‘Royal Opal’, which has ice-blue flowers with yellow centers in September. These asters make good ground covers.
Callistephus chinensis group includes China Aster and Annual aster. It is native to China and Korea, and it is cultivated worldwide as an ornamental plant. White Aster Needle sometimes called ‘White Spider Aster’ is distinctive for its narrow petals and makes a wonderful addition to any garden. White Spider asters make long lasting nice cut flowers.
Asters attract birds, butterflies, bees and other kinds of species.
Asters have different number of petals depending on their type. A common daisy-like species has 5 petals (ray florets) and 5 sepals (parts of the calyx of a flower, enclosing the petals and typically green and leaflike), having the same color and length of petals.
Another kind of aster has about 21 petals or more. They come in different shades of pink, purple, yellow, red, blue and white, with a center disk having colors of yellow to dark orange (disk florets).
Asters prefer a deep, reasonably light, moderately fertile soil, growing best in full sun or partial shade. Overly dry soil encourages the growth of powdery mildew. During the dormant season, keep the soil from becoming soggy to prevent root rot. Asters are sometimes plagued with fungal diseases.
The most common is wilt disease which causes the leaves and the entire stems to yellow and wilt; powdery mildew and botrytis, a gray buzz that appears on buds and flowers. Excessive nutrients aggravate all three of these diseases in the soil.