How to Grow and Care for China Aster

China asters (Callistephus chinensis) are long-blooming cool-weather annual flowers that will fill your borders with a vibrant rainbow of colors from summer to fall. There are many cultivars and shades to choose from with these prolific plants that often receive comparisons with their chrysanthemum relatives. They come in varying heights with single, semi-double, and double bloom formations that work wonderfully in cut flower arrangements.

China asters can easily grow in rich, well-drained, evenly moist soils. They like a full sun or partial shade position.

China Aster Care

Here are the main care requirements for growing China asters:

• Place in full sun or partial shade.
• Plant in fertile, well-drained soil.
• Water regularly to keep the soil evenly moist.
• Space plants well apart to ensure sufficient air circulation.
• Support tall cultivars to prevent flopping.
• Fertilize twice monthly during the growing season.
  

Light

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.

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.

Water

Even moisture encourages the healthiest growth in China asters. They could need watering as often as twice weekly. Consider mulching around the roots to help preserve moisture and reduce the risk of drying out.

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.

Fertilizer

China asters appreciate regular fertilization during the growing season. A balanced all-purpose water-soluble formula will work well. Steer clear of high-nitrogen fertilizers, which encourage foliage rather than bloom growth and can promote disease.

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.

Growing China Asters From Seed

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:

1. Wait for the blooms to be spent and the seeds to ripen. This typically happens mid-fall.
2. 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.
3. 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.
4. 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.
5. Press the seeds into the soil mix, but don't cover them with more than 1/8 of an inch of soil.
6. Provide access to bright light for successful germination.
   
7. Seeds should germinate within 10 to 20 days.
8. 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.

Common Pests & Plant 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.

How to Get China Asters to Bloom

It's all about the beautiful flowerheads when it comes to China asters. Learn more about how to encourage bountiful blooms.

Bloom Months

Typically, China asters bloom sometime between early summer and mid-fall. However, how long your plants bloom and at what time of year depends on the cultivar, your climate, and when you sow the seeds. For example, some cultivars appear in late spring, die back in the heat of the summer, and reappear in the fall. Some others put on a show from late summer to mid-fall.

How Long Do China Asters Bloom?

The average bloom time for China asters is around six weeks. Some cultivars might put on a show for as long as two months with the right care and climate.

What Do China Aster Flowers Look and Smell Like?

The blooms of China asters vary in size depending on the cultivar but can be as large as 3 to 5 inches wide. Colors include red, pink, white, purple, yellow, and blue. There are three types of flower heads: the daisy-like single form, semi-double blooms, which have more petals but the center of the flower is still visible, and ornate double forms with multiple layers of petals. Even though they have little fragrance, their showy appearance makes up for it.

How to Encourage More Blooms

Regular even watering of well-drained soil, fertilization, and enough light are all crucial for encouraging abundant blooms. Thin out groups of flowers if there's a danger of overcrowding—China asters need plenty of air circulating to stay healthy.