How to Grow Chinese Aster Callistephus 

Popular for its vibrant colorful flowers, the Chinese Aster plant (Callistephus chinensis) is the perfect way to introduce late season color to your flower garden.

Part of the Asteraceae family along with daisies and chrysanthemums, unlike other aster plants the Chinese Aster is cultivated as an annual plant, not a perennial.

The Chinese Aster is a distinctive addition to the flower garden.  

What is a Chinese Aster?

Callistephus is a distinctive plant, similar in appearance to other members of the aster family. Unlike other aster flowers which produce colorful flower clusters on each stem, the Chinese Aster produces only one flower per stem.

As the common name suggests, the Chinese Aster is native to China and Korea. Since the 1980s breeders have developed a range of different cultivars and hybrids. This has helped to boost the popularity of this once uncommon plant.

Today’s modern specimens are more colorful than the traditional Callistephus plants. They also produce sturdier stems. These are better able to support the flowers and are largely wilt resistant. Adding further interest, the stems of modern cultivars produce alternating green leaves.

Also known as the Summer Aster, Callistephus plants are typically hardy in USDA Zones 2 to 11. The plants are best planted in moist, well draining soil and a full or partial sun position. The sturdy stems can, in favorable conditions, achieve a height of around 3 ft. This makes them ideal for including in the middle or back of a mixed flower bed.

Modern Chinese Aster plants flower in a range of colors including white, red, pink, purple, yellow and blue with a bright yellow center. The large flowers can measure 3 to 5 inches wide.

Popular for their large flowers, the Chinese Aster adds late season color to gardens.   

Whilst garden stores and plant nurseries sell young plants, or transplants, that are ready for planting out in the garden, you can also grow Chinese Aster from seed.

Popular Types of Callistephus

While traditional varieties remain popular, newer cultivars and hybrids are starting to dominate the market. Bright and colorful, these are also more resilient than traditional types.

The variety of Chinese Aster plants currently on offer range from compact dwarf cultivars to tall, 3 ft types. Take the time to research the plants, selecting the best varieties for your garden.

Some of the most common Callistephus cultivars include:

• Lilliput Blue Moon which produces attractive, disc-like flowers,
• Matsumoto, which is one of the most well known double flowering cultivars,
• Valkyrie, a reliable hybrid which produces needle-like flowers,
• King Size, popular for its large, double flowering blooms.

There is an increasingly colorful range of Chinese Aster plants available.

The Crego series is ideal for the back of a bed or border. Reaching 18 to 36 inches in height the double flowers, identified by their curled petals, bloom in shades of pink, red, purple and white.

Another reliable series is Giants of California. Producing full and semi-double blooms in shades of pink, purple and white, the petals are similar to those of the chrysanthemum. Giants of California plants reach a height of 28 to 36 inches.

The range of color and height makes these plants an ideal addition to the flower or cottage garden.

How to Grow Callistephus From Seed

The Chinese Aster is one of the easiest plants to grow from seed.

Start the seeds undercover 6 to 8 weeks before your last average frost date.

Sow in seed starting trays filled with a fresh seed starting mix. Moistening the soil helps the seeds to stick in place. Sow as thinly as possible before covering with a light layer of compost.

Place the seeds in a propagator in a light position. The temperatures should average 70 to 72 ℉. If the temperature falls too far below this range the seeds may struggle to germinate. Using a Bonviee Seed Starter Tray with Adjustable Humidity Dome better enables you to control the temperature and humidity levels around your seeds and seedlings.

Germination usually takes around 14 days. During this period it is important not to let the soil dry out.

Sow seeds on a moist seed starting mix.  

When the seedlings produce their first true set of leaves you can carefully transplant them into small, individual pots filled with fresh potting soil.

Continue to grow the plants undercover until all danger of frost has passed. The young Chinese Aster plants can then be hardened off before transplanting outside.

Starting Seeds Direct

If you do not have the room to start seeds undercover, you can sow your Callistephus seeds directly into their final growing position.

Wait until all frost danger has passed and the soil has started to warm up before sowing the seeds.

As the soil warms up, take the time to weed the flower bed. This is also the best time to dig in any necessary nutrients or improvements that your plants may require.

When you are ready to sow, moisten the soil before sowing the seeds as thinly as possible. Don’t worry if they cluster too closely together. You can thin the seedlings out after germination. Aim to sow the seeds 3 inches apart, gently pressing them into the moist soil.

Seeds typically sprout in 3 weeks. Protect the seeds and young seedlings from slugs and potential damage with Agribon Floating Row Covers.

After sowing carefully sprinkle a light layer of compost over the seeds.

When the seedlings have 2 to 3 sets of true leaves they can be thinned out. Depending on the variety you can thin out your Chinese Aster seedlings to a spacing of 9 to 12 inches.

Where to Grow Callistephus

While they prefer soil with a pH ranging between 5.5 and 7.5, Callistephus plants grow in most soil types as long as it is well draining and watered regularly.

Best planted in a rich soil, work in organic matter such as well-rotted compost or leaf mulch before planting. Dig the soil down to a depth of around 6 inches.

Chinese Aster plants are at their best in full sun positions. While they also tolerate partial shade, flowering may not be as prolific.

Summer Aster plants are best placed in a light, open position. 

How to Transplant Callistephus Seedlings

Before transplanting the Chinese Aster seedlings, moisten the prepared soil. It should be saturated, not soaking wet.

Make a hole in the prepared soil and plant the seedling to the same depth as the root ball.

Space your Chinese Aster plants out so that they have plenty of room to grow. Most types require spacing 9 to 12 inches apart. Mature Callistephus plants can achieve a height, depending on the variety of 8 to 36 inches and spread 12 to 18 inches wide. Giving young Chinese Aster plants lots of room to grow helps to prevent overcrowding and encourages air flow. This reduces the risk of fungal disease developing.

Following germination and transplanting it can take between 90 and 120 days for the plants to mature and set flower. If you want a long lasting, successive floral display sow fresh seeds every 2 weeks.

Growing Callistephus in Pots

Not the most reliable choice for a container garden, you can start Callistephus seeds undercover and transplant into pots, or start them directly in their containers.

While Chinese Aster plants do grow in pots, they are shallow rooted specimens. If the soil is allowed to dry out they can struggle and even fail. Even if the plants do recover, growth and flowering may be negatively impacted.

Plant Callistephus in pots that are at least 10 inches deep and 2 inches wider than the mature plant dimensions. Fill the pots with a fresh potting soil and plant as described above.

Caring for Callistephus

Unlike native, perennial asters, Chinese Aster plants are not self-sufficient. This means that they require more care and attention.

Correctly caring for the plants promotes healthy growth and flowering. 

How to Water

The main care requirement for Callistephus is regular watering. Water the plants deeply, at least once a week if it doesn’t rain. Whilst the plants are best planted in well draining soil and require lots of regular watering, be careful not to allow the soil to become waterlogged. This can cause issues such as root rot.

Do not allow the soil to dry out. Sitting in dry soil for a prolonged period can stress the plants, making them vulnerable to pests and disease.

Lightly mulching around the plants helps the soil to retain moisture. An organic mulch of leaf mold, shredded bark or wood chips is ideal. When applying the mulch, do not allow it to contact the plant. This can cause infestation or disease. A layer of mulch also suppresses weed growth.

When to Fertilize

Apply a regular dose of balanced, slow release granular fertilizer throughout the growing season.

Do not apply a fertilizer that is rich in nitrogen. Too much nitrogen encourages excess foliage production. This often comes at the expense of flowering.

Weeding and Deadheading

Weed around the plants regularly. Keeping the soil neat and tidy helps the plants to stay healthy and productive. A layer of mulch, as we have already noted, helps to suppress weed growth.

Deadhead the spent flowers as they fade. This encourages more blooms to form.

As the flowers fade you can either cut them back to the ground, tidying up your flower bed, or let the withering stems remain in place over winter. This provides wildlife with shelter as well as winter interest.

Plant Support

Taller varieties may require some support to prevent them from toppling over. Tie bunches loosely to a HAINANSTRY Garden Plant Stake.

Do not tie the plants too tightly together. This can prevent airflow, causing issues such as powdery mildew to develop.

Taller specimens may require some support.  

Common Callistephus Problems

Correctly cared for, Callistephus plants are largely problem free.

Be careful not to overwater your Chinese Aster plants. Wet or soggy soil can cause issues such as root rot to develop. Similarly, watering the plants too infrequently can cause stress. A soil moisture sensor is a great investment if you struggle to know how often to water your plants.

Correctly spacing the plants and keeping the leaves dry when watering helps to prevent issues such as powdery mildew. Other issues such as Aster Yellow, Leaf Spot, Blight and Fusarium Wilt can also affect Chinese Aster plants. Trim away affected foliage.

Regularly inspect the foliage of your Chinese Aster plants for signs of infestation. Aphids, leafhoppers and spider mites are common pests.

While most infestations can be washed away with a blast from a garden hose, more severe infections may require treatment with an application of neem oil or insecticidal soap. For more information on how to use neem oil on plants, our in depth guide is a good place to start.

A good way to add late season color to beds and borders, the Callistephus is an increasingly popular garden flower. The sturdy stems of many hybrid cultivars mean that it is also a good addition to the cut flower garden.

While the plants are attractive clustered together they also work well when planted alongside zinnias.

Other good combination plants include

• Alstroemeria,
• Black-Eyed Susan,
• Coneflower,
• Dahlia,
• Sunflower,
• Phlox,
• Aster.

Increasingly popular in late summer and early fall gardens, Callistephus is an attractive addition to the garden.