Pocket Botanist
Check these first
- Measure the hours of direct sunlight the plant receives.
- Check if the plant is being shaded by taller trees or buildings.
- Look for signs of new growth that is thin and pale.
Likely causes
Insufficient light
Most likelyHow to tell: The stems are long, thin, and leaning heavily toward the nearest light source.
What to do: Move the plant to a spot that receives full sun for the entire day. If it is in the ground, you may need to transplant it to a brighter location in the spring.
Lack of pinching
PossibleHow to tell: The plant is tall and sparse with very few side branches.
What to do: Pinch back the top few inches of growth in late spring. This encourages the plant to branch out and grow into a bushier, shorter shape.
Find out what's wrong with your smooth blue aster
The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.
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When to worry
It is serious if the stems are so weak they fall over completely. Some legginess is normal if the plant is nearing the end of its blooming cycle.
Stopping it coming back
Pinch the stems back by one third in late May to keep the plant compact and sturdy.
Smooth Blue Aster: leggy growth? Check yours with a photo
Every plant is a little different. Take a photo of your smooth blue aster and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.
Scan with your phone's camera to get the app
Or go to pocketbotanist.app/get on your phone
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Questions people ask
- Can I cut it back now?
- If it is mid-summer, you can still trim it back, but you might get fewer flowers. It is best to do this in late spring.
- Does fertilizer cause legginess?
- Yes, too much nitrogen fertilizer can cause rapid, weak growth. Asters generally do not need extra feeding.
More problems with Smooth Blue Aster
Back to the Smooth Blue Aster guide
This article was generated with AI on from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.