Plants from the genus Callistephus are half or full hardy annuals.
They are bushy in nature and range in height from 20 to 80 cm.
The blooms of Callistephus are similar to those of chrysanthemum.
They flower in the summer in almost all colours, they often have a yellow centre.
The common name for this garden plant is the China Aster.
In the garden these plants look great as part of a border; they are also used often as a cut flower in arrangements.
These are not the easiest of plants to care for.
Both Photographs of China Aster (Callistephus chinensis) by Carl E Lewis
There is only one member of the Callistephus genus, the China Aster (Callistephus chinensis). As the name suggests the plant is a native of China. Plants carry long, toothed ovate leaves of about two to three inches in length (5 to 8 cm) and usually have chrysanthemum like flowers, though some varieties may have only simple ray florets. In many cases the central disc florets are yellow in colour. Outer petals are of many colours; purple, red and pink are very common. The original native species carries single white flowers.
As it is a popular garden plant there are many different varieties available, meaning that the species is available with many different petal colours and sizes; dwarf varieties may be as little as 8 inches (20 cm); taller varieties may reach 32 inches (80 cm).
Some of the commonly grown varieties of Callistephus chinensis include Lilliput blue moon, Pink tower, Ostrich plume, Blue ribbon, Hulk, Red ribbon and Seastar.
As a member of Asteraceae (the daisy family) Callistephus is closely related to species such as Chrysanthemum, Calendula, Tagetes, and Dahlia.
Common Names: China Aster.
Life Cycle: Half hardy annual, hardy annual.
Height: 8 to 32 inches (20 to 80 cm).
Growing Region: Zones 1 to 10.
Flower Details: Rays: purple, red, blue, pink, many other colours. Discs: yellow. Ray and (sometimes) disc florets. Chrysanthemum-like. Fragrant.
Foliage: Ovate. Toothed. Two to three inches.
Sow Outside: Cover seed. Following the last frost. Spacing 6 to 24 inches (15 to 60 cm).
Sow Inside: Water from below. Use vermiculite. Use Peat pots. Germination time: one to two weeks. Temperature 65 to 70°F (18 to 21°C). Seven or eight weeks in advance. Transplant outdoors following the last frost.
Requirements: Full sunlight or light shade. Good drainage. Soil pH 5.5 to 7. Rich soil. Regular light watering. Feed with fertilizer two times during the growing season. May need support. Summer mulch. Deadhead. Weed around plants to prevent competition. Grow in a different location every year. Do not overcrowd. Do not grow close to a surface that reflects heat. Grow in an area that has adequate ventilation. It is important to remove plants that have any sign of disease as they pass infections easily to other Callistephus.
If planning to grow Callistephus then the seeds should be lightly covered once sown. Sow in the spring, following the last frost.
If you plan to grow China Aster and similar as seedlings indoors for later transplanting then they should be germinated at a temperature of 18 to 21C for two weeks. Seeds should be sown in peat pots in a vermiculite mix and water supplied from below. After about seven or eight weeks the seedlings can be planted in the garden in an area of partial shade or full sun with a spacing of 20cm (dwarf) 40cm (medium) or 60cm for larger species. They prefer to grow in a rich soil that has good drainage and a pH of 6 to 7.
Callistephus chinensis are not the easiest plants to look after, they should be carefully watered when it is dry and require a couple of feeds when growing. Additionally they should be staked, dead headed and require careful weeding of plants in the area; it is good to rotate Callistephus's location every year. Further information on caring for Callistephus is given in the quick growing guide above.