Aster plant pruning is a must if you want to keep these perennial flowers healthy and blooming abundantly. Pruning is also useful if you have asters that grow too vigorously and are taking over your beds. To do it well you only need a few tips on perennial pruning.
Asters are classic fall-blooming perennials that provide a welcomed burst of color just as many other flowers are fading. Native to North America, these hardy plants are low-maintenance and easy to grow, rewarding you with daisy-like flowers well into autumn. But to keep asters looking their best season after season, it’s important to know when and how to cut them back properly in fall.
Overview of Fall Care for Asters
There are many types of asters, from short bushy varieties to tall plants reaching several feet high. Most produce abundant flowers in shades of purple, pink, red, white or blue. Caring for asters in fall includes:
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Deadheading spent blooms to encourage more flowers.
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Cutting plants back after flowering finishes to keep them tidy
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Leaving healthy foliage in place until it naturally deteriorates.
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Mulching around the base to protect roots from cold.
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Avoiding excess fall fertilizing that can stimulate growth prone to winter damage
Properly pruning back asters at the right time in autumn is especially important for their health and performance
When to Cut Back Asters in Fall
Asters should be cut back after they have completed flowering for the season. This is usually sometime in late fall. The ideal timeframe is typically:
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After several hard frosts or freezes cause the foliage to die back.
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After the plants look spent, wilted and mostly finished for the year.
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Anytime from late fall to early winter, before snowfall arrives.
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Around the time of the first hard frost but delay if still flowering.
The goal is to time it late enough that asters won’t try to regrow or reflower, but early enough to tidy them up for winter.
How Far to Cut Back Asters in Fall
When cutting asters back in fall, most varieties can be safely pruned quite low to the ground. The optimal height is:
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Prune back to 2-3 inches above the soil surface.
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Remove spent flower stalks and dead foliage down to basal growth or ground level.
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Cutting lower minimizes overwintering sites for some pests and diseases.
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But don’t prune lower than about 2 inches to avoid damaging the crown.
Leaving lower basal growth intact allows the plants to put out fresh new stems and foliage quickly again next spring.
Tools to Use When Cutting Back Asters
To prune back asters, bypass pruners or garden shears are ideal tools to use:
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Bypass pruners – Makes clean cuts on individual stems up to about 1⁄2 inch thick.
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Garden shears – Quickly cut back many larger or thicker stems at once.
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Hedge shears – Allow efficient pruning of very wide rows or plantings.
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Loppers – Extend your reach to the centers of large plants.
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Chainsaw – Only necessary for very overgrown, woody asters if needed.
Sanitize tools before and after use to prevent spreading diseases. Pruning saws work well on thicker wood.
Step-By-Step Process for Cutting Back Asters
Here is a simple step-by-step procedure for cutting back your asters in fall:
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Wait until after several hard frosts when plants look completely dormant and spent.
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Remove any fallen leaves or debris around the base of the plants.
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Start by cutting off any dead or damaged growth down to live stems.
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Prune spent flower stalks back down to the foliage or lowest live growth.
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Next, shear back the remaining leaves and stems to about 2-3 inches above soil level.
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Rake away and dispose of the finished foliage debris when done pruning.
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Mulch freshly pruned plants with 2-4 inches of shredded bark or leaves.
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Clean and disinfect your cutting tools.
Your tidy, cut-back asters are now ready for winter!
What to Do With Pruned Aster Trimmings
Once your asters are cut back for the season, you’ll have a fair amount of foliage and plant debris leftover. Here are some options for dealing with the trimmings:
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Compost the plant waste to create rich organic matter for amending garden beds. Just be sure no diseases were present.
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Add pruned foliage to the compost pile as browns or carbon material.
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Use clippings as winter mulch for protecting other garden plants by laying them over beds.
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Bag up the debris and set it out for municipal yard waste collection if available.
Just ensure any diseased foliage is disposed of or destroyed to avoid spreading issues to other plants.
Avoid Cutting Asters Back Too Early
It’s important not to cut asters back too prematurely in fall before they’ve gone fully dormant:
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Shearing plants while still actively growing can trigger a flush of less attractive late season growth.
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Pruning too early may reduce flower production the following year.
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Wait until well after flowering finishes and several hard frosts or freezes occur.
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Delay pruning if warm spells cause new growth or intermittent flowering.
Give those late season blooms a chance to flourish before cutting plants back!
Reasons for Cutting Asters Back in Fall
Here are some of the key benefits of properly timing your fall asters pruning:
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Removes spent, fading flowers that can harbor pests and diseases if left.
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Eliminates overwintering sites for some damaging pests.
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Prevents self-seeding in areas where asters spread aggressively.
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Reduces winter damage to top growth exposed to cold winds and weather.
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Encourages fresh, new growth from the base the following spring.
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Promotes better air circulation to minimize foliage diseases.
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Improves the tidy, attractive look of the winter garden.
Preventing Damage When Cutting Back Plants
To avoid harming your asters when cutting them back:
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Never prune lower than about 2-3 inches above soil level.
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Use sharp, clean pruners or loppers to avoid crushing stems.
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Make angled cuts just above healthy buds or leaf nodes.
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Disinfect tools before and after each use.
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Take care not to cut or damage lower crown growth.
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Don’t leave stubs by cutting too far above ground level.
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Rake away all cut debris to prevent pests or disease carryover.
Ongoing Fall and Winter Care
Keep supporting your asters after fall pruning with these additional care measures:
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Apply 2-4 inches of shredded leaves or bark around the base as winter mulch.
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Water whenever soil dries if winter is mild to prevent desiccation damage.
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Place evergreen boughs over crowns for extra insulation in very cold regions.
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Cover loosely with row cover fabric to protect from heavy snow or ice accumulation.
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Consider spraying with an anti-desiccant leaf sealant before extreme cold sets in.
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Remove mulch or coverings next spring once all danger of frost has passed.
Benefits of Proper Fall Cutting Back
Some of the advantages of cutting asters back at the ideal time each year include:
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Promotes bushy, compact basal growth the following spring.
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Removes any insect eggs or disease spores on spent foliage.
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Tidies up the garden’s appearance before winter arrives.
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Reduces the need for staking of floppy growth next year.
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Minimizes overwintering hideouts for certain pests.
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Improves air circulation and light penetration at soil level.
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Encourages prolific flowering on vigorous new stems.
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Maximizes winter survival and cold hardiness.
When to Leave Asters Alone in Fall
Some scenarios when you may opt to skip cutting back asters in fall include:
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When fall remains very mild with minimal frost or freezing.
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If plants are still actively growing or flowering into winter.
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In warmer climates where winter weather won’t damage tender growth.
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To provide seed heads for birds and winter interest in the garden.
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To promote self-seeding and naturalizing in appropriate areas.
But in most cases, following best fall pruning practices will give you the healthiest plants.
FAQs About Cutting Back Asters in Fall
Here are answers to some commonly asked questions:
How short can I cut back asters?
It’s safest to leave 2-3 inches of growth to avoid harming the crown and next year’s buds.
Should I cut back asters before winter?
Yes, pruning in late fall just before winter allows you to tidy up the beds once flowering ends.
Do I need to prune asters every fall?
Annual pruning is recommended to maintain vigor, promote blooming, and improve their shape.
What do I do with asters in winter?
Mulch the base after fall pruning to insulate roots. Leave stems and foliage for insulation too.
Do asters come back every year?
Most asters are hardy perennials that will return each spring to re-bloom provided they are growing in suitable conditions.
With the proper timing and technique, fall is an ideal time to cut back your asters to keep them flowering abundantly. Do your pruning when plants have gone dormant after a hard frost or freeze for best results.
Do Asters Need to Be Pruned?
Asters do not strictly need to be pruned, but there are some good reasons to do it. One is simply to maintain a shape and size that you like. Especially if you have rich soil, these flowers will grow abundantly. Pruning them back can prevent the need to stake them and give the plants more pleasing shapes. Thinning them out will also keep your plants healthy and reduce the risk of mildew developing. Finally, by pruning asters, you will get a greater abundance of flowers throughout the growing season.
How to Prune an Aster Plant
There are several ways to prune perennials, but asters respond best to two strategies: thinning and pinching. Thinning is the best strategy to prevent mildew if this is a concern in your beds. To thin your aster, cut off entire stems at the base in the spring. About one in three stems is a good general rule for cutting back asters. If your main goal is to get as many flowers as possible from one plant, pinching is the best way to prune it. As the name of the technique suggests, all you need to do this is your fingers. You will pinch off the growing tips and the first sets of leaves on stems of the plant. Pinch them off just above the node for the best results. Pinch asters from midspring to early summer. Pinching promotes the growth of more blooms because it encourages more branching in the aster plant. The main new growth on a stem is at the very top. If you cut that off, you send more nutrients to the side branches, which helps them grow. Careful pinching and thinning is easy with asters and great for promoting healthy plants and abundant blooms. Deadheading spent blooms throughout the growing season can also promote additional flowering.
