How to Dig Up Dahlias and Store Them for Beautiful Blooms Year After Year

The dahlia is a cherished member of the aster family, producing lush, attractive blooms. Its flowers come in many different colors, sizes, and styles, so there's bound to be one that's a perfect fit for your garden.

Naturally, you'll want to keep your dahlias healthy for as long as possible, but that can be difficult when the temperature starts to drop. Dahlias are typically propagated by tubers, and these tubers are only cold-hardy in zones 8 and above—so they will struggle in colder regions.

But there's a solution: Digging up the tubers at the end of the season and storing them safely until next year. Here's how the experts say to do it.

When to Dig

Timing is everything when digging up dahlia tubers. You don't want to remove them from the ground too early, but you also don't want to wait until the soil is frozen.

"You'll know when the dahlias are ready to dig up when the first hard frost blackens the foliage," says horticulturist Kate Walz. "This is also called the killing frost. Once the leaves and stems turn dark, mushy, or wilted, the dahlia tubers are no longer storing energy, and the plant has gone dormant."

How to Do It 

Start by cutting back the plants. "After the killing frost, the dahlia stems should be cut back to 4 to 6 inches above the crown of the plant," says Walz. "[This] is important because any remaining energy from the plant will consolidate in the tubers; it also makes the clump easier to handle when lifting it from the soil."

After cutting back, you can wait a week or two before digging up the tubers, provided the temperatures don't drop too low. This waiting period allows the tubers to form eyes, which are necessary for their later growth. However, if a heavy freeze is predicted, then it's better to dig up the tubers immediately.

Use a pitchfork to loosen the soil around the plant, and then dig deep to lift the clump of tubers. Do this carefully. If you dig too closely to the clump, you'll risk accidentally piercing the tubers.

How to Store

There are many different ways to store dahlia tubers; it may take some trial and error to find the method that works best for you. 

Inspect

Before storing, thoroughly inspect the tubers and remove any that are damaged or rotting. The tubers should be completely dry—damp ones can be subject to root rot. Brush or rinse off any excess soil.

Make a Box

Walz labels each clump with a waterproof plant tag and places it in a cardboard box.

"The box is filled with slightly crumpled newspaper, and I layer them inside, keeping them from touching each other as best I can," she says. Author Teri Speight recommends wrapping up the tubers in shredded newspaper.

Newspaper isn't the only option. Some gardeners nestle their tubers in vermiculite, wood shavings, or peat moss. A container with ventilation is ideal.

Store It

Walz closes then closes up the box and stores it in an unheated garage for the winter. "I check on them every month to make sure nothing is rotting or covered in mold. I wait until the spring to do any clump divisions."

Speight places her box—she also uses recycled onion bags—in her laundry room or basement. "I usually hang the mesh onion bags from the ceiling," she says. "If I place them in a box, I place the box in an out-of-the-way space on a lower shelf or floor."

The key is to make sure the space is not too humid or too dry, and that the airflow is sufficient. It's a good idea to label your bag or box, so you can remember the tuber color and variety.

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Tips and Tricks

Storing dahlias is a nuanced process, and often requires a bit of trial and error. Thankfully, the pros have a few pieces of advice.

Avoid Damage

Treat your tubers delicately when digging them up. "Dahlias have tender, brittle necks," says Walz, referring to the narrow part that connects each tuber to the crown. "If you dig too close with a shovel or pull hard on the stalks, you can snap those necks. A broken neck means the tuber usually can’t sprout next year, even if the rest of it looks plump and healthy."

Explore Storage Options

Experiment to find what works for you. "Everyone seems to have their own preferred method for dahlias," says Walz. "It's a good idea to try a few different ways and see which works best for you and your environment."

Don't Dig

If you live in zones 8 or higher, then your dahlias may survive through the winter in the ground. However, there are exceptions.

"If I have planted one of the older cultivars, I tend to leave them in the ground and mulch heavily," says Speight. "In my zone 7b garden, the winters have been rather mild. I periodically check them over the winter, making certain they don't heave as the ground thaws."