China Aster (Callistephus chinensis)

Annual Aster, Aster Sinensis, China Aster

China Aster, Callistephus chinensis, is a member of the Asteraceae family that includes the chrysanthemum and daisy. Unlike other aster varieties, this particular species is not a perennial, but an annual. Bloom time is from late summer into fall, when it fills gardens and containers with cheerful flowers in vibrant tones.

I. Appearance and Characteristics 

Callistephus is a monotypic genus of flowering plants in the aster family, Asteraceae, containing the single species Callistephus chinensis. Its common names include China aster and annual aster. And it is cultivated worldwide as an ornamental plant in cottage gardens and as a cut flower.

This is an annual or biennial plant with one erect, mostly unbranched stem growing 20–100 cm (7.9–39.4 in) tall. The alternately arranged leaves vary in shape or size. The basal leaves usually fall away before flowering. Leaves around the middle of the stem are a few centimeters long and are borne on winged petioles. The blades have serrated edges. Leaves toward the top may have smooth edges. The large solitary flower head grows at the top of the stem and sometimes on branches. The head is lined with layers of phyllaries, those in the outer layer large and leaflike, measuring up to 3 centimeters long. The inner layer can be purple-tinged. The head contains one or two rings of ray florets, most often in shades of reddish purple. The flowering period is from August to October in the northern hemisphere.

This plant is a naturalized species in some areas outside of its native range (Indochina, Europe, North America, Australia, New Zealand, etc.) and can be found on the edges of deciduous forests. It grows at altitudes from 300 to 2700 above mean sea level. As an ornamental plant it thrives on fresh, nutrient-rich, easy-humus rich soils in warm humid air conditioning.

This species has been grown and bred extensively in cultivation. Cultivars are available with flowers of many colors, varying heights, and single and double heads. In the wild, they are purple in color. There are several cultivars with flowers of different colors. Cultivars with flowers of other colors were obtained in particular by hybridization.

The plants are susceptible to fusarium wilt, a fungal disease. Some cultivars are more resistant to this than others. Pest insects can include leafhoppers, aphids, blister beetles, and the tarnished plant bug. The plant is also susceptible to mites.

II. How to Grow and Care

Sunlight

China asters can be grown in full sun or partial shade. You’ll see the best blooms on your plants in cooler climates if you grow them in a sunny spot. In hot regions, midday shade is beneficial.

Temperature and Humidity

China asters aren’t good flowers to choose for sultry deep south regions. These cool-weather annuals appreciate temperate climates to produce abundant blooms. When summer soil temperatures rise above 75 degrees Fahrenheit, blooming often stops and then resumes for a short period as temperatures drop in early fall. Mulching can help keep roots cool when temperatures rise.

Watering

The China aster requires moderate watering compared to similar trees. This species grows best if it is regularly watered in well-draining soil. Regular watering is especially important for the first two years after planting. This species should be watered near the root base after the first two inches of soil have become dry.

Soil

China asters grow best in rich, well-draining soil. Mixing in some organic matter when planting or sowing seeds improves drainage and adds nutrients to promote vigorous growth and profuse blooming.

Fertilizing

The china aster should be fertilized with a water-soluble, quick release fertilizer every two weeks during the active growing season between spring and fall. This species can also be fertilized with an organic fertilizer like fish emulsion. Nitrogen-rich fertilizers should not be used.

Planting Instructions

China aster is easy to start from seed. When starting indoors, sow seeds six to eight weeks before the last spring frost date. If sowing directly in a garden bed, sow seeds after the last spring frost date with successive plantings at two-week intervals. Cover the seeds with 1/8 inch of soil and keep the soil moist. With a soil temperature of 65-70°F, the seeds should germinate in 10-15 days. The plants appreciate good air circulation, so thin the seedlings to 6-12 inches apart. Tall varieties may require staking or other support.

Pruning

Propagation

Another selling point of the China aster is that it’s super easy to propagate by seed. Follow these steps to increase the chances of bountiful blooms:

  • Wait for the blooms to be spent and the seeds to ripen. This typically happens mid-fall.
  • Hang the cut plants with the spent blooms facing down in a cool, dry place to gather the seeds. Place a sheet underneath to catch the falling seeds as the plant dries out. Help things along with a vigorous shake.
  • Start the cold-sensitive seeds indoors in a tray with a thin layer of starting mix six to eight weeks before the last expected frosts. Harden off gradually and transfer outside once the seedlings appear and the soil is consistently warm.
  • Alternatively, sow directly outside once the soil temperature is consistently above 70 degrees Fahrenheit. Rotating plant sites is best to minimize the risk of spreading diseases.
  • Press the seeds into the soil mix, but don’t cover them with more than 1/8 of an inch of soil.
  • Provide access to bright light for successful germination.
  • Seeds should germinate within 10 to 20 days.
  • Thin out the seedlings so there is at least 6 to 12 inches of space between them to provide adequate ventilation.

By sowing more seeds every two weeks right into mid-summer, blooms could still appear well into the fall if temperatures remain mild enough.

Potting and Repotting

China aster is a shallow-rooted plant that grows well in containers as long as the soil never dries out. Choose a container an inch wider than the mature plant, making sure it has drainage holes. Fill it with commercial potting soil and add the plant. Spread a layer of mulch on the soil to retain moisture, and water the plant at its base once a week.

Pests and Diseases

Although China asters are easy to grow, they are susceptible to some diseases. Some of the issues to look out for include:

  • Aster fusarium wilt: a soil-borne fungal disease that causes the leaves to brown and wither. Unfortunately, it isn’t treatable, so it is best to remove any infected plants (never burying or using as compost) and pick wilt-resistant cultivars going forward or plant new flowers in a different site, as the fungus can linger in the soil.
  • Aster stem and root rot: Another nasty soil-borne fungal disease that attacks the roots, stems, and lower leaves. Prevent the problem by planting in a well-drained site and avoiding overwatering. If rot sets in, planting new flowers in a different site is best.
  • Aster yellow: This bacterial disease is rarely deadly to plants, but it can cause stunted, warped growth, discolored foliage, sterility, and poor blooms. Aster leafhopper insects are vectors for the disease, so removing infected plants and controlling leafhopper populations is the best course of action.

Aphids and spider mites are also fans of China asters. It’s possible to get rid of aphids and spider mites with an organic pesticide before a major infestation takes hold.

III. Types of China Aster

One of the perks of China asters is that there are so many cultivars to choose from. Here are just a few options to consider:

  • Callistephus chinensis ‘Crego Giant’: A tall cultivar, growing up to 36 inches, with semi-double blooms that flower from mid-summer to early fall in various shades.
  • Callistephus chinensis ‘Ostrich Feather’: The double bloom formation has a unique, shaggy appearance. Available in various shades, including pink, white, red, purple, and blue and grows up to 24 inches tall.
  • Callistephus chinensis ‘Matsumoto’: This is a classic semi-double cultivar, popular for cut flower arrangements and resistant to fusarium wilt. Various petal colors surround a yellow flower center.

III. Uses and Benefits 

C. chinensis makes an eye-catching addition to beds and borders. Mix colors, or plant drifts of a single color to suit your own personal style. Add them to your cutting garden beside companionably tall zinnias.

C. chinensis makes an eye-catching addition to beds and borders. Mix colors, or plant drifts of a single color to suit your own personal style. Add them to your cutting garden beside companionably tall zinnias.

Asters may not bloom until late in the season, but the sturdy green foliage of C. chinensis provides a lush backdrop for other flowers that are in bloom, as well as providing a neutral filler between other ornamental specimens.

IV. Plant China Companion Plants

Coral Bells

Exciting new selections with incredible foliage patterns have put coralbells on the map. Previously enjoyed mainly for their spires of dainty reddish flowers, coralbells are now grown as much for the unusual mottling and veining of different-color leaves. The low clumps of long-stemmed evergreen or semi-evergreen lobed foliage make coralbells fine groundcover plants. They enjoy humus-rich, moisture-retaining soil. Beware of heaving in areas with very cold winters.

Marguerite Daisy

For a spectacular show during cool weather, plant marguerite daisy. Often confused with shasta daisy, marguerite is more mounded and shrubby. Different types also come in pink with a bloom resembling purple coneflower. Marguerite daisy’s hallmark is that it loves cool weather—and blooms best in most areas in spring and fall, though it will continue to bloom through the summer in mild-summer areas. Even when it’s not in bloom, the dark green, finely cut foliage looks good against just about any light-color flower.

Fountain Grass

Like many grasses, fountaingrass is spectacular when backlit by the rising or setting sun. Named for its exceptionally graceful spray of foliage, fountaingrass also sends out beautiful, fuzzy flower plumes in late summer. The white, pink, or red plumes (depending on variety) continue into fall and bring a loose, informal look to plantings. This plant self-seeds freely, sometimes to the point of becoming invasive.

China Aster (Callistephus chinensis) Details

Common name Annual Aster, Aster Sinensis, China Aster
Botanical name Callistephus chinensis
Plant type Annual
Hardiness zone 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b
Height 2 ft. 0 in. - 3 ft. 0 in.
Width 2 ft. 0 in. - 3 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition High Organic Matter
Flower color Blue
Leaf color Green