Asters require little to no pruning except in late fall or early spring, when they may be cut back to just a few inches above the ground. In spring, they may be thinned or divided to promote air flow, and in late spring to early summer they can be pinched back to stimulate more lateral branching. Remove the spent flowering stems after blooming to prevent self-seeding and keep the plants looking tidy.
The quick answer: Thin crowded aster stems in early spring, then pinch or cut fall-blooming asters back by up to half in late spring or early summer. Stop by early July so they have time to set flower buds. Deadhead faded flowers to prevent self-seeding, and cut the plants back to a few inches above the ground in late fall, or leave the stems standing for birds and cut them back in early spring.
Cutting spent flower stems from an alpine aster after it blooms.
Most garden asters, such as New England and New York asters, bloom in late summer and fall. This calendar is for those fall-blooming types.
When
What To Do
Why
Early spring
Cut back any stems left from last year, thin about a third of the new stems, and divide crowded clumps
Clears old growth, improves airflow and refreshes tired plants
Late spring to early July
Pinch stem tips or cut the plant back by up to half
Creates a bushier, sturdier plant with more flowers and less flopping
During and after bloom
Deadhead faded flowers
Keeps plants tidy and prevents unwanted seedlings
Late fall or early spring
Cut stems back to a few inches above the ground
Prepares for new growth; leaving stems until spring feeds birds
Stop pinching by early July. Fall asters form their flower buds in late summer. Pinching or cutting back after early July in northern areas, or mid-July in warmer areas, can delay or remove the fall bloom. Asters that bloom in late spring or summer, such as alpine aster, should not be cut back before they flower. Trim them after blooming instead.
When To Prune Asters
Asters may be pruned in early spring to remove any foliage or stems damaged during winter. Then in late spring to early summer, you can cut back the plant by half to encourage more growth and blossoms in the fall. Finish this cutback by early July. Keep the plants deadheaded through the bloom season to maintain a tidy appearance and prevent self-seeding. Asters may be pruned back to just a few inches above the soil line in late fall when they have finished flowering.
Dried aster flowers can be cut back in late fall or left standing to feed birds over winter.
How To Prune Asters
Asters do not require pruning except to maintain shape and encourage a bushy appearance. Use clean, sharp pruners or garden shears, and work on a dry morning when the foliage is not wet.
Clean up in early spring. Cut back any of last year’s stems that are still standing, and remove dead crowns from the center of the clump.
Thin crowded stems. Thin the plant by removing approximately a third of the stems at the base using pruning shears.
Pinch or cut back in early summer. Cut back to half its height in late spring or early summer, no later than early July, to create a bushier plant and more blooms in fall.
Deadhead during bloom. Remove spent flowers. When most of the flowers on a stem have faded, cut the entire flowering stem back.
Cut back at season’s end. Cut stems to a few inches above the ground in late fall, or wait until early spring if you want to leave seed heads for birds.
Pinching Asters And The Chelsea Chop
Tall asters, especially New England asters, often flop over by the time they bloom. Cutting them back before they flower makes them shorter, sturdier and fuller. There are two ways to do it.
Pinching
Use your fingers or pruners to remove the top 2 to 3 inches of each stem, just above a set of leaves. Pinch once or twice between late spring and early July. Each pinched stem branches out, giving you more flower stems and a rounder plant.
The Chelsea Chop
For a faster method, shear the whole plant back by a third to a half in June. To stretch the bloom season, cut back only half of the stems in a clump. The uncut stems will bloom first, and the cut stems will follow a little later.
How To Deadhead Asters
Deadheading keeps asters looking neat and stops them from dropping seed around the garden. New England asters in particular can self-seed heavily.
Single flowers: Snip faded blooms just above the next bud or set of leaves.
Whole stems: When most flowers on a stem have finished, cut the stem back to the base of the plant.
Late in the season: Consider leaving some seed heads in fall. Goldfinches and other birds eat aster seeds.
Skip it if you like: Many compact asters, such as Henry™ asters, are covered in small flowers and do not need deadheading.
When To Cut Back Asters: Fall Or Spring?
You can cut asters back in either late fall or early spring. Both work, so the choice depends on the health of your plants and what you want from the garden over winter.
Cut Back In Late Fall If…
Wait Until Early Spring If…
The foliage had powdery mildew or other disease
The plants were healthy
You want to limit self-seeding
You want to feed birds and shelter overwintering insects
You prefer a tidy bed over winter
You enjoy the look of seed heads in winter
“I don’t hurry to cut back my asters. I grow a few native asters, like blue wood aster (Aster cordifolius), in my woodland garden and leave them standing over winter for the birds and for winter interest. We’ve had a few hard freezes, and they’re still standing. I may cut back my New York aster (Aster novi-belgii), though, since it flopped over my tiarella.”
If you wait until spring, cut the old stems back before new growth gets tall. For more on fall and winter tasks, see aster winter care.
Why Prune Asters?
Asters do not strictly need pruning, but a few simple cuts make a big difference. Thinning the plants helps to promote air circulation, which will reduce the risk of powdery mildew forming on the foliage. Pinching or cutting back in early summer keeps tall varieties from flopping and produces more flowers. Deadheading ensures that the flowers will not go to seed and keeps the plant looking tidy.
Dividing overgrown asters
If the aster plant is overgrown by the end of the season and too big for the space, the plant can be divided and replanted the following spring. Most asters benefit from division every two to three years, or when the center of the clump starts to die out. A small clump can be replanted in the original location, and the new clumps can be transplanted elsewhere in the garden. Discard the old, woody center.
Fading white aster flowers can be deadheaded to keep the plant tidy and prevent self-seeding.
Do Asters Come Back Every Year?
Perennial asters, including New England, New York, aromatic, heath and wood asters, come back every year. The top growth dies back in winter, and new shoots emerge from the roots in spring. Many also spread slowly and may self-seed.
China asters (Callistephus chinensis) are different. These are annuals, often sold in flats or seed packets, and they will not return the next year. Check the plant tag: names like Symphyotrichum or Aster usually mean a perennial, while Callistephus means an annual.
Common Aster Problems Pruning Can Fix
Problem
Likely Cause
What To Do
Floppy stems
Tall variety, rich soil or too little sun
Pinch or cut back by half in early summer next year
White powder on leaves
Powdery mildew, often from crowded growth
Thin stems in spring, divide crowded clumps, and remove infected foliage in fall
Bare or dead center
Clump is overdue for division
Divide in early spring and replant the healthy outer sections
Cut asters back to a few inches above the ground in late fall after they finish blooming, or in early spring before new growth gets tall. For bushier plants, you can also cut fall-blooming asters back by half in early summer, no later than early July.
Do asters come back every year?
Yes, perennial asters such as New England and New York asters come back every year. China asters are annuals and do not return.
How do you deadhead asters?
Snip faded flowers just above the next bud or set of leaves. When most flowers on a stem are done, cut the whole stem back to the base. Leave a few seed heads in fall if you want to feed birds.
Should I cut back asters in the fall?
You can. Fall cleanup is best if your asters had powdery mildew or you want to limit self-seeding. If the plants were healthy, you can leave the stems standing over winter for birds and cut them back in early spring.
Can I cut back asters in summer?
Yes, but only until early July for fall-blooming asters. Cutting back later can remove the flower buds that form in late summer.
How far back should I cut asters?
In early summer, cut back by up to half the plant’s height. At the end of the season, cut stems down to a few inches above the ground.
How often should asters be divided?
Most asters do best when divided every two to three years in early spring, or whenever the center of the clump starts to thin out.
Bottom Line
Asters need only light pruning to look their best. Thin stems in early spring, pinch or cut back fall-blooming asters by up to half before early July, and deadhead faded flowers to prevent self-seeding.
At the end of the season, cut the plants back in late fall, or leave the stems standing for birds and cut them back in early spring. Divide clumps every few years to keep them healthy and blooming well.
Sources
University of Maryland Extension: Perennials
University of Illinois Extension: Plant Asters for Unique Display of Fall Color
Clemson Cooperative Extension Home & Garden Information Center: New England Asters
Chris Link is the co-owner of Plant Addicts and helps gardeners find the right plants for their yards, homes, and growing conditions. Plant Addicts has helped millions of gardeners shop for plants and learn how to care for them.
Originally published August 29, 2022. Last updated November 2026.
