Key Points
Asters are popular late summer perennials, sometimes grown as container annuals for fall color.Deadheading asters regularly helps to prolong their bloom time and encourage bigger blooms.When deadheading asters, remove spent flowers closest to a healthy bud or leaf node, and don’t cut too much of the stem.
Asters are a must-have in the late summer garden to provide plentiful color lasting through autumn and beyond. Many aster cultivars, including New England asters, tolerate some early frost, so they’re great to have once summer perennials start to go dormant. Whether tall and swaying, or short and compact, the many varieties of aster flowers really light up the late-season border in a rainbow of color possibilities.
Keeping your aster plants neat and trimmed accentuates their beauty, but deadheading is also important to help promote bigger and longer-lasting blooms. We spoke with some horticulture experts to get tips for the best timing and methods for deadheading asters.
Meet the Expert
Mary Jane Duford is a horticulture expert, master gardener, and the founder of the gardening website Home for the Harvest.
Rhonda Kaiser is a master gardener and experienced horticulturist who lives in Texas, and author of the book The Vintage Farmhouse Garden.
When to Deadhead Asters
The best timing for deadheading asters is based on two factors. First, they should be deadheaded as soon as blooms begin to fade. Second, it’s very important to start deadheading them before any of the flowers form seeds, says Mary Jane Duford, a horticulture expert. Duford says that deadheading before asters go to seed ensures the plant focuses its energy on new bud growth, which in turn extends the blooming season.
Asters should be deadheaded regularly to encourage new growth and keep plants tidy, says Rhonda Kaiser, a horticulturist and author. The faded flowers should be trimmed throughout the blooming season, which is typically late summer into early fall.
Duford recommends every few days, or at least every two weeks during the peak blooming time, and reminds gardeners not to wait until the entire plant is covered in dead flowers before deadheading. Unlike some perennials that may only need deadheading just before they go dormant, deadheading asters and other late-season flowers should be done frequently to promote growth and new buds.
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How to Deadhead Asters
These simple steps are the best way to deadhead your asters, according to Duford.
Locate spent flowers: Once the aster bloom begins to fade or droop, or when it starts to turn brown, it’s time to trim it off.Look for nearest healthy leaf or bud: You will want to trim the spent flowers close to a healthy leaf or bud to encourage new growth and direct more energy to the emerging buds.Snip off spent blooms: Snip off the spent flowers and compost them. If you do find the flower has started producing seeds, you can save them to scatter in spring.
Why Is Deadheading Asters Important?
Duford says that deadheading asters is crucial to keeping them thriving and blooming throughout the fall season in the garden. Removing old blooms reduces the risk of rot and disease, she says. Duford also warns that leaving asters untrimmed can leave them looking messy (especially taller heirloom cultivars).
There is also the possibility that asters may stop flowering earlier in the fall, if left untrimmed, and this means a shorter season of beauty in your garden or your autumn container displays.
Best Tips for Deadheading Asters
Here are a few tips to keep in mind when deadheading asters.
Use clean, sharp snips or pruners: Always make sure your pruners are clean and sharp, says Kaiser. Clean any cutting tools regularly to avoid the potential spread of bacterial or fungal disease to your plants.
Don’t cut too much: Be careful not to cut too far down the stem of your asters, warns Duford. Remove only the flower head and a small part of the stem. This is because the plant needs to retain some energy to keep producing buds and flowers.
Remove clusters once faded: Kaiser says that, because asters have a tendency to bloom in clusters, you can also remove the entire cluster stem after flowers have faded. To avoid removing too much from one stem at a time, don’t trim all the spent clusters on the same day.
Keep deadheading until frost: Duford recommends regularly deadheading your asters until the first hard frost.
Leave some stems untrimmed to save seeds: Duford says you can save some seeds to replant in the spring if you leave a few stems of blooms untrimmed and let them go to seed. Choose stems that are not too prominent (lower down on the plant or in the back) so they won’t detract from the colorful new blooms.
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