How to Grow: China Asters
How to Grow: China Asters
Pronunciation: ka-LIS-te-fus chin-EN-sis
China Asters (Callistephus chinensis) are a lovely addition to the cutting garden.
There are many types of Asters, including popular cultivated and wild native Perennial types. However, here we are going to discuss only the Annual blooming China Asters (Callistephus chinensis).
“Optimo Alpha Light Blue” and “Optimo Red”
There’s a reason why China Asters are so popular as a cut flower. They are sturdy, tough and long-lasting in the vase. They also come in wide range of colors and shapes. Some of them even resemble fluffy Peonies!
However, China Aster can be a bit tricky to grow, since they are “day length” sensitive and must be planted at juuuuust the right time to achieve good stem length (more about that later).
They also can be susceptible to some difficult disease issues, depending on where you live.
Because of these challenges, I categorize China Asters as best for “Experienced Growers”.
On our farm, we love growing a variety of China Asters as both a Focal Flower (large flower that is the focus of a bouquet) and Filler Flower (medium-sized flowers that complement the Focal Flowers).
Some China Asters will produce 8-12 large flowers on long stems, while others may produce dozens of smaller flowers on a “spray” type stem (one main stem with multiple flowers).
“Optimo Red” and “Optimo Alpha Light Blue”
Let’s look at the Pros and Cons of growing China Asters for cut flower use.
PROS
They come in a multitude of colors, sizes and types.
They are very sturdy plants.
The flowers are durable and not easily damaged by handling.
The flowers “hold” for a long time in the field, giving you a long window of opportunity to harvest the blooms.
They often produce multiple blooms per plant.
They have an excellent vase life of 7-10 days with proper harvest and care.
CONS
They must be planted at a specific time due to day-length sensitivity. If this “window of opportunity” is missed, the plants will likely bloom on short, unusable stems.
They are not a good candidate for “succession planting” since they perform best when planted at a specific time.
They are very susceptible to Aster Yellows disease, which is spread by leafhoppers and thrips. If you live in an area where Aster Yellows disease is common, you may have a difficult time growing healthy plants (this is a BIG challenge for us!).
They can experience “Aster Rot”, a fungal infection that causes the plant to rapidly wilt and rot.
CHOOSING SEEDS
There are lots of different types of China Asters you can try, so choose ones that have colors and shapes that please you.
Be sure to look for varieties that reach a minimum of 24” tall. Many China Asters are sold for bedding plant/landscape use and won’t be tall enough for cut flower use.
The following China Aster series are a great choice for cut flower use:
Azumi X
Bonita
Matsumoto
Optimo
Tower
“Optimo Red”
Here are a few of my favorite China Asters to grow for cut flower use:
Azumi X “Rose”
Tower “Chamois”
“Optimo Alpha Light Blue”
HOW TO SOW
China Asters are easy to grow from seed in trays. Bury seeds about ⅛ deep and keep seeds moist and warm until germination occurs in 10-14 days.
Transplants or Direct Sow?
China Aster should be transplanted. Direct sowing is not recommended.
Sow seeds indoors 6-8 weeks before your Average Last Spring Frost. They should be transplanted out after the threat of frost when the soil is warm.
It’s important to transplant the seedlings promptly so they can grow as much as possible before the Summer Solstice occurring around June 21(ish) in the Northern Hemisphere. As the days shorten after the Solstice, the plants begin to set their blooms and the stems will not grow much taller.
Ideally, you want the plants to grow as tall as possible before the Summer Solstice to get the longest stems possible.
“Succession Planting” is not recommended for China Asters, since transplanting additional successions later in the season will result in short, unusable stems.
“Optimo Alpha Light Blue”
PLANT SPACING
Most varieties can be grown at 6-12” spacing. We usually grow at 9” spacing, but could grow most varieties closer for more efficient use of space. Closer spacing will encourage longer stems as the plants compete for light.
“Bonita Shell Pink”
GROWING ON
If you live in an area where Aster Yellows disease is a problem, I recommend covering the seedling with insect netting IMMEDIATELY after transplanting. You can find my favorite insect netting and clamps HERE. This will help to protect the plants from leafhoppers and thrips.
If the plants DO show signs of Aster Yellows or Aster Rot, remove them immediately and throw them away (do not compost). Be sure to rotate where you plant China Asters each year to help prevent disease issues.
To reiterate, it’s important to transplant the seedlings promptly so they can grow as much as possible before the Summer Solstice occurring around June 21(ish) in the Northern Hemisphere. As the days shorten after the Solstice, the plants begin to set their blooms and the stems will not grow much taller.
Ideally, you want the plants to grow as tall as possible before the Summer Solstice to get the longest stems possible.
Fertilize and water the plants regularly when the plants are young and actively growing. Once the buds begin to form, back off on feeding but continue watering.
The plants are sturdy but still benefit from netting or support to keep the stems straight.
Pinching is generally not necessary or recommended, however some types may benefit from it. If desired, you could experiment by pinching a few plants and comparing them to unpinched plants. Note: This is how I discovered Optimo series does NOT like to be pinched! ;)
STAGE OF HARVEST
China Asters bloom in mid to late summer (usually around mid-August on our farm in Michigan). Unlike other flowers, China Asters have a long “harvest window”, so there is no rush to harvest them.
Harvest when the outside florets begin to open. Single stem types can be harvested one stem at a time, while spray types do best as a whole plant harvest (cut the entire plant off at the ground).
“Tower Chamois”
POST-HARVEST CARE
China Asters require no special treatment after harvest.
QUESTIONS?
Ask them here and I’ll get back to you!
Ready for more?
If you’re serious about growing the garden of your dreams this year, register for my online course, “Backyard Cutting Garden 101”. You’ll find everything you need to plan, grow, harvest and arrange your stunning blooms. I can’t WAIT to help you grow! Click on the button below for all the details.
