Dahlias are an incredibly rewarding addition to any garden; not only are they vibrant in colour, but their petal pattern is quite a sight to behold. This is why it's so saddening when they stop blooming towards the end of autumn.
If you know how to grow dahlias, you'll know that the journey from tuber to the first bloom is a long yet worthwhile one. And while there's lots of effort needed to keep them alive over winter, before you start bidding them farewell for the cold seasons, there's a way to prolong those mesmerising blooms just a touch longer.
As well as planting late summer flowers, finding ways to keep them around for longer is key. With that in mind, we've consulted with plant experts to find out how you can prune your dahlias to prolong blooming.
How to prune dahlias for more blooms: expert advice
Whether you've grown your dahlias from seed or from tubers, once they've begun blooming, caring for them is the same process. And that includes pruning.
"The most important pruning job for dahlias is deadheading (removing flowers as soon as they've finished rather than allowing them to produce seed)," says Dr Russell Sharp, Founder of Eutrema. |All you need is a clean, sharp pair of bypass secateurs or flower snips (make sure they're sharp because blunt tools can crush the stem)."
Once you've got your essential gardening tools at the ready, the method is similar to pruning roses to maximise blooms.
"Start by identifying a flower that's finished blooming, making sure you don't confuse it with a new bud. Once you've found the right stem, don't just snip the flower head off. Follow the stem down until you reach the first strong pair of leaves or a healthy side shoot, then make a clean cut just above that point," explains Dr Russell. "This encourages the plant to produce new flowering stems instead of wasting energy on seed production."
"Repeat this every few days throughout the flowering season because dahlias produce flowers continuously, and the more regularly you deadhead them, the more energy the plant puts into producing fresh blooms. While you're pruning, remove any damaged, broken or diseased stems as well, as this improves airflow through the plant and helps keep it healthy for the rest of the season," he adds.
Adding this to your regular summer gardening to-do list will really pay off and keep your dahlias looking their best for longer.
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How do you cut dahlias so they keep blooming?
Whilst there are plenty of plants you should never prune in summer, dahlias will definitely benefit from it, but only if you do it properly.
"Check your plants every few days and remove blooms as soon as they start to fade, and make sure you can tell the difference between a spent flower and a developing bud," says Dr Russell.
"A faded flower has a pointed, slightly elongated shape, while a new bud is round and firm. Many gardeners accidentally remove unopened buds, which reduces the number of future flowers," he points out.
"Regular deadheading tells the plant to keep producing blooms because it hasn't completed its natural cycle of setting seed, and the more regularly you remove old flowers, the longer the plant will continue flowering through late summer and into autumn," continues Dr Russell.
What month do you cut back dahlias?
Although it's recommended to prune your dahlias during summer, the intense cutting back doesn't need to be done until autumn or winter. And don't make an autumn garden mistake by cutting them back too early.
"It's best after the first hard frost, so usually in October or November, depending on where you live. Frost turns the foliage black and soft, which is the signal that the growing season has finished. At that point, cut the stems back to around 10-15 centimetres above ground level," begins Dr Russell.
"If you're lifting the tubers to store them over winter, leave a short section of stem attached as it makes the tubers easier to handle. Don't be tempted to cut dahlias back heavily in late summer while they're still actively flowering because you'll remove healthy growth that is still producing energy for both flowers and next year's tubers," he adds.
To avoid this summer gardening mistake, just stick to pruning and deadheading, then you can save that huge cut back when the frost naturally ends the season.
If you don't know how to overwinter dahlias, it's a good idea to learn, as this will ensure you can enjoy annual blooms from the flowers as well as stop them from dying in the ground over autumn and winter.
