Key Points
Deadheading dahlias regularly is key to a long, vigorous blooming season.Fading blooms should be deadheaded as soon as the flower centers start opening.Making deep cuts when deadheading encourages a bushy plant and long stems.
Dahlias are a staple in the late summer garden. But if you aren’t regularly harvesting your dahlia flowers for bouquets, should you still be deadheading the flowers as blooms begin to fade?
We asked two dahlia farmers for their input, and they agreed: regular deadheading is essential to a long and vigorous growing season.
Here’s everything you need to know about deadheading dahlias, plus expert tips for keeping your plants blooming well into the fall months.
Meet the Expert
Shelly Deaton is the co-founder of EarthSpoke Farms, a small multigenerational family flower farm growing dahlias and other blooms in Mendocino, California.
Melanie Harrington is the owner and head grower at Dahlia May Flower Farm, a small family-run farm growing dahlias and other blooms in Trenton, Ontario, Canada.
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When Should You Deadhead Dahlias?
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Alex Manders / Getty Images
Regular deadheading encourages dahlias to produce more blooms, a stronger branch structure, and a longer growing season. So when is the right time to deadhead a fading bloom? It’s probably earlier than you think.
“You should always deadhead just as the flower center begins to open and the back petals of your bloom start to fade,” says Shelly Deaton, co-founder of EarthSpoke Farms in Mendocino, California.
Deadheading once the flower center starts to show will prevent the plant from putting energy into going to seed, thus encouraging more flowers and extending your growing season well into the fall months.
“To simplify the science, a plant’s main goal in life is to produce a seed, which will continue its linage,” says Melanie Harrington, owner and head grower at Dahlia May Flower Farm in Trenton, Ontario, Canada.
“If you leave your spent flowers on your plant to form seed, your dahlia gets the message that it’s fulfilled its mission, and it will not continue to place energy into producing new blooms.”
So, although it may feel counterintuitive to snip those half-decent-looking blooms off your plant, it will pay off in the long run. As a bonus, even the partially spent blooms look gorgeous in a vase inside on your table!
How to Deadhead Dahlias Like a Pro
Deadheading is a relatively simple concept, but the pros have a few rules they always follow to keep their dahlia plants flourishing.
First, where you make your cuts on the plant matters. According to Deaton, making deep cuts just above a lower set of leaves is key, whether you’re deadheading or harvesting your flowers.
“New flowering stems will sprout from the leaf nodules, and cutting deeply will encourage your plant to produce stronger and longer stems from those nodules and will help build a bushier plant to support those next blooms,” she says.
Next, it’s essential to understand that as the season progresses, you’ll likely need to deadhead your dahlias more often to keep the plant blooming. This is because, as the cool weather moves in, it signals to the dahlia plant that the season is almost up and it’s time to go to seed.
As a result, you’ll notice that your blooms will start to open their centers more quickly so the bees can do their work, Deaton says. At this stage, regular deadheading is more important than ever to keep your plant blooming.
“If you follow this approach, dahlias should keep blooming until your first hard frost,” Deaton says. “But as winter approaches, don’t be surprised if a dahlia plant’s flowers are not quite as well-formed compared with early and mid-season blooms.”
Expert Tips for Gorgeous Dahlias
Credit:
EarthSpoke Farms
Aside from deadheading, regular fertilizing and watering are key to happy dahlias and beautiful blooms, especially in the heat of the late summer.
“Dahlias, a plant native to the mountainous regions of Mexico and Central America, often struggle during the long hot days of summer, but they thrive in the fall, as the temperatures drop and we enjoy cooler overnight temperatures,” Harrington says.
If your area is prone to heat waves and drought in the summer, Harrington recommends watering your dahlia plants deeply two to three times a week in the early morning or late evening to keep them hydrated.
Running a sprinkler in the garden once or twice a week can also help stave off foliage pests like spider mites that are quick to move in when conditions are arid.
As for fertilizing, Harrington notes that dahlias benefit from monthly feeding with a fertilizer that is high in phosphorus and potassium, and low in nitrogen, such as a 5-10-10.
“If you keep your plants well watered and frequently fertilized in the summer months, you’ll be rewarded with an abundance of blooms in the fall, and a healthy tuber harvest after the first frost!” she says.
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