Learn About Aster
How to Sow
Sowing Directly in the Garden:
- Sow in average garden soil in a sunny area after danger of heavy frost. In the deep South, Gulf and Pacific Coast areas, sow from fall to early spring.
- Select a location in full sun with good rich moist organic, well-drained soil.
- Prepare the bed by turning the soil under to a depth of 6-8, inches removing any debris, and lightly raking as level as possible.
- The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
- Sow in rows 15-18 inches apart.
- Sow seeds evenly and cover with 1/4 inches of fine soil.
- Firm the soil lightly and keep it evenly moist.
- Seedlings will emerge in 14-21 days.
- Thin to at least 18 inches apart when seedlings have three sets of leaves. Up to 36 inches for tall varieties.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their germination.
- Mulches also help retain soil moisture and maintain even soil temperatures. For annuals, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
- Keep soil evenly moist but not wet.
- Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
- “Deadhead”, remove spent flower heads to encourage continuous flowering and prevent seed development.
- Plants need good air circulation to avoid powdery mildew.
- Asters are sensitive to the length of the day. They will not bloom until late summer but should bloom until frost.
- Annual asters, also called China Asters, make great cut flowers. Cut when blooms are 2/3 open.
- Use in beds and borders, they work in containers too, although keep in mind they will not bloom until late in the season.
Common Pests and Problems
Aster Yellows: Plants are stunted, develop witch's brooms (excessive growth), petals turn green and become deformed. This virus-like condition is spread by leafhoppers. Burpee Recommends: Remove infected plants and control leafhoppers. Remove weeds in the area which serve as alternate hosts to the disease.
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Fusarium Wilt: Caused by a soil-borne fungus, the fungus enters through the roots and passes up into the stem producing toxic substances. Burpee Recommends: Destroy affected plants at the first sign of fusarium.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and keeping weeds under control. Contact your Cooperative Extension Service for fungicide recommendations.
Rust: A number of fungus diseases that cause rust colored spots on foliage and stalks. Burpee Recommends: Make sure plants have good air circulation. Remove infected plants. Contact your Cooperative Extension Service for fungicide recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cabbage Looper: These worms are green with a white stripe on either side, about 1-1.5 inches long. Burpee Recommends: Hand pick. Floating row covers can help prevent their laying eggs on the plants.
Leafhoppers: Leafhoppers cause injury to leaves and stunt growth. They also spread disease. Burpee Recommends: Remove plant debris. Use insecticidal soaps. Consult your Cooperative Extension Service for other insecticide recommendations.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticid
I thought asters were hardy perennials? Many asters are hardy perennials but the annual aster, or China Aster, is not hardy and is grown as an annual.
Are they good for cutting? Yes, they are excellent for cut flowers! Cut when 2/3 of the way open.
Why haven’t my asters bloomed? These are day length sensitive plants that bloom when the days are shorter, at the end of summer. Give them time!
Can I grow China aster in containers? Yes, just be mindful that they will not bloom until later summer, so combine them with summer bloomers. Make sure the container is large; they grow 24 inches tall, and use a commercial potting mix.
Do China aster attract pollinators? Yes they are butterfly magnets!