Dahlias are one of the most stunning flowers that add late-season color to your garden. With their vibrant hues and blooms ranging from tiny round balls to giant dinner-plate sized flowers, dahlias provide eye-catching texture, color, and interest to your late summer and fall garden. These flowers bloom profusely from mid to late summer until the first frost.
Dahlias are categorized into different groups based on flower size and shape, such as single, cactus, pompon, waterlily, and so on. Because of the sheer number of varieties, these flowers fit in many garden styles, from cutting gardens to old-fashioned cottage gardens. Pollinators love them, too, and they grow well in either landscape beds or containers.
Technically, dahlias are perennials and can be left in ground for the winter in USDA zones 8 and warmer (find your zone here). “But they must be lifted after the first frost in the rest of the country because they will not survive freezing temperatures,” says dahlia grower Andy Hunter of Lynch Creek Farm Dahlias. “They also do not like heavy soils such as clay, which stay too wet and cause tubers to rot.”
Ahead, here’s how to dig up and save your tubers for next spring– and for years to come:
Wait for the First Frost or Two.
Once you have a killing frost, dahlias go from green to black overnight, says Hunter. Wait a week or two, then cut the plant down to leave about 6 inches of stem above the soil line.
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Dig Around the Plant to Loosen the Soil.
Use a garden fork or spade to dig a circle around the clump, about a foot from the center stem. Work your tool up and under the clump, then lift it out of the hole. But be gentle so you don’t accidentally damage the crown, where the stems emerge, says Hunter. Side note: If your dahlia is in a container, you can dig it up, or you can store it in the container in an unheated place, such as the basement, until spring.
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Clean Off the Soil.
Rinse off as much dirt as possible, then let the clump dry in a covered location for a few days. Don’t let the clumps freeze, says Hunter. Make sure the tubers are absolutely dry, including the hollow stem, which can collect moisture, until moving on to the next step.
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Store the Clump.
Place the clump in a clean container, and layer with vermiculite, peat moss, or white wood or cedar shavings. Do not cover the container with a lid to prevent condensation from building up, says Hunter. Some growers also use a paper bag filled with these materials.
Keep the Container from Freezing.
Place your container somewhere in a cool place where they won’t freeze, such as a basement. “The ideal temperature range is 40 to 45 degrees,” says Hunter. Check on the tubers once a month to ensure they aren’t getting mushy (too wet) or shriveling up (too dry). Remove anything that is rotting and give tubers a spritz of water if they are too dry.
Divide the Tubers.
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When it’s time to plant next spring, inspect your clumps and toss any mushy ones or those with broken necks. Don’t get discouraged if a few didn’t make it; some cultivars are more challenging to overwinter than others, says Hunter.
Next, separate the clump into individual tubers by cutting through it with a knife. A viable tuber needs at least one eye, which is where the plant will grow from. “Dahlias don’t have eyes on the tuber itself like a potato does,” says Hunter. The eye is found on the crown area (where the stem will emerge to grow above ground). The eye looks like a small whitish or reddish bump when dormant.
You can divide in the fall, but it’s also okay to do so in the spring—and it may be easier to see the eye as it breaks dormancy and begins to sprout.
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