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Dividing dahlias is a quick and easy way to propagate them, meaning you'll get more plants for free. And, as one of the best summer bloomers, boasting a stunning spectrum of colors and forms, who wouldn't want to multiply their stock?Dahlias produce more of their fleshy tubers each growing season, resulting in often-large clumps. Every year or two, healthy sections can be carefully cut apart and replanted.
It can be a little more fiddly than dividing other plants, but you'll be rewarded with lots more flower power for your borders and pots.Below, you'll find a practical guide on how to try this trick at home, with lots of expert insights from horticulturist Peggy Anne Montgomery from Flowerbulb.eu.
Whatever types of dahlias you're growing, it's definitely worth giving it a go.Dahlias are the perfect choice for a cutting garden (Image credit: Jacky Parker Photography / Moment / Getty Images)A step-by-step guide for dividing dahliasIf you're looking for spring gardening tasks, be sure to add this to your list. According to Peggy Anne, the best time to divide dahlia tubers is in the spring - just before planting.
1. Dig up your dahliasBe careful not to damage the tubers as you lift them (Image credit: Olga Seifutdinova / iStock / Getty Images Plus / Getty Images)The first step in dividing dahlias is to dig them up from the ground. You may have already done this.
If you experience cold winters where you live, you will need to do this in the fall anyway to overwinter them. This is because they are tender plants that are easily damaged by freezing temperatures and wet soil.Peggy Anne says to wait until the first frosts have blackened the foliage, and then cut the stems down to about six inches.
'Use a garden fork or shovel to carefully dig around the plant, lifting the entire clump without damaging the tubers. Remember that they have grown since you planted them, so give yourself plenty of room when digging.'Once you've retrieved the bundle of dahlia tubers from the ground, Peggy Anne recommends shaking or brushing off the excess soil, or rinsing them with water.
After this, let them dry in a well-ventilated, shady area for a day or two.2. Locate the right points to split your tubersDahlia 'eyes' can be various colors, including purple or brown (Image credit: AndreaObzerova / iStock / Getty Images Plus / Getty Images)It's important to split your dahlias at the right points.
To do so, Peggy Anne says to locate the 'eyes' on the tubers, which are small growth nodes where new shoots emerge. 'They are on the stem where the tubers attach,' she says, highlighting how each divided tuber must have at least one eye to grow into a new plant.You may end up with some singular tubers, and some small clusters.
'It is far better to make fewer divisions if it's difficult to see the "eyes",' Peggy Anne adds.3. Divide the tubers using a sharp toolCut the clusters of tubers apart carefully (Image credit: AndreaObzerova / iStock / Getty Images Plus / Getty Images)Once you're confident on exactly where to divide your dahlia tubers, you can start making the cuts.
'Use a sharp, clean knife or pruning shears to cut tubers apart at natural divisions,' says Peggy Anne. To prevent spreading any dahlia diseases, it's best to disinfect your tool between cuts (Peggy Anne recommends dipping pruning shears in alcohol, and you can do this with your knife, too).Remember to check the quality of the tubers as you go.
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4. Store or plant, depending on the time of yearThe best time to plant dahlias is in the spring. Many gardeners start them off undercover, then plant them outdoors once frosts have passed.
If you're planting your tubers straight after dividing them, Peggy Anne recommends allowing the cut surfaces to dry for a few hours to prevent rot. Each division can then be planted into its own pot, and kept somewhere frost-free for growing on. Don't forget to harden them off before moving them into your yard.
If, however, you're storing the tubers for the winter, Peggy Anne says to place them somewhere cool (40-50°F) and dry, in vermiculite or sawdust, until spring.'Label tubers if you're growing different varieties,' she adds. If you're looking for plastic alternatives for your garden, you could try these bamboo plant labels from Amazon.
FAQsWhat should you do if you can't see the 'eyes' of your dahlia tubers?If you're trying to divide your dahlia tubers in the fall but are unsure where the 'eyes' are, Peggy Anne recommends waiting until spring, when they become more visible.How many plants can you grow from a dahlia tuber?This depends on the size of the clump – as long as each division has an 'eye', you may be able to split it five or more times, resulting in plenty of new plants.Dividing dahlias may seem daunting at first, but it's worth the effort.
Plus, as Peggy Anne says, 'Doing is learning; you will become better at it every year.'Continue caring for these plants correctly, including keeping an eye out for dahlia pests and deadheading them when they start to bloom, and you will have a beautiful – and bigger – summer display..
