Categories: Flowers & Shrubs

How to Store Dahlia Tubers Over Winter

Dahlias give you months of big, bold flowers, but in most of North America, they won’t survive winter in the ground. The good news? Their tubers keep well indoors if you treat them right. Here’s how to store dahlia tubers over winter, from the first frost to spring planting, so you can grow the same favorites year after year.

Key Takeaways

Dig tubers about a week or two after frost blackens the foliage.
Let them dry for a day or two, but don’t let them shrivel.
Store them at 40°F to 50°F in a slightly moist material like peat moss or wood shavings.
Check them once a month for rot or shriveling.

Do You Need to Dig Dahlias?

It depends on your zone. NC State Extension lists dahlias as hardy in zones 7 to 10. So in the warmer parts of that range, many gardeners simply cut the stems down and cover the bed with a thick layer of mulch. However, wet winter soil rots tubers fast, even where it rarely freezes.

In zone 6 and colder, the ground freezes deep enough to kill them. That covers most of the Northeast, the Midwest, the Rockies, and Canada. If you garden there, plan to dig and store dahlia tubers indoors each fall.

When to Dig Dahlia Tubers

Wait for the first killing frost. The leaves will turn black and limp almost overnight. Then cut the stalks back to about 4 to 6 inches.

After that, leave the tubers in the ground for another week or two if the weather allows. This short rest helps the skins toughen, so dahlia tubers store better. Still, dig before the soil freezes hard.

How to Store Dahlia Tubers Step by Step

1. Lift the Clump Gently

Push a garden fork into the soil about a foot away from the stem. Work around the plant, loosening the soil as you go. Then lift the whole clump from underneath. Don’t pull on the stalk, because the neck where each tuber meets the stem snaps easily.

2. Remove the Soil

Shake off loose soil. Some growers rinse clumps with a gentle spray of water, which makes it easier to spot eyes and damage. Either way, cut away any tubers that look mushy or broken.

3. Label Every Clump

Write the variety on a plant tag or directly on a tuber with a permanent marker. Otherwise, you’ll be guessing next spring.

4. Let Them Dry Briefly

Set clumps upside down in a garage or shed for a day or two, so water drains from the hollow stems. Keep them out of freezing temperatures. However, don’t dry them for weeks, or they’ll shrivel.

Dig tubers after the first frost blackens the foliage.

5. Pack Them in Storage Material

Next, nestle the tubers in a box, crate, or paper bag filled with a slightly moist material. Good choices include:

Peat moss or coir: Both hold a little moisture and are easy to find.
Wood shavings: Pet bedding works well and breathes nicely.
Vermiculite or perlite: These are clean and light, which helps if you stack boxes.
Plastic wrap: Some growers wrap single divisions tightly. It works, but check for mold more often.

Make sure the tubers don’t touch each other. That way, if one rots, it won’t spread.

6. Pick the Right Spot

The ideal place to store dahlia tubers stays between 40°F and 50°F. A cool basement, an attached garage that stays above freezing, or an unheated closet often works. Above 50°F, tubers may sprout early. Below freezing, they die.

Should You Divide Now or in Spring?

You can divide clumps in fall or wait until spring. In fall, the skins are softer and easier to cut. In spring, on the other hand, the eyes are swollen and easier to see. Either way, each division needs a piece of the crown with at least one eye, or it won’t grow.

If you’re new to dahlias, storing whole clumps and dividing in spring is the simpler route.

Check on Them Over Winter

Once a month, open the boxes and look over the tubers.

Shriveled tubers: Mist the packing material lightly. As a result, they’ll often plump back up.
Soft or moldy spots: Cut them out with a clean knife and dust the wound with sulfur or cinnamon. Then discard any tuber that’s mushy all the way through.
Early sprouts: Move the box somewhere cooler.

Label each clump by variety before storing.

Getting Ready for Spring

About four to six weeks before your last frost date, you can pot up tubers indoors for a head start. Alternatively, plant them straight in the garden once the soil reaches about 60°F, usually around the time you’d plant tomatoes.

While you’re tidying the beds this fall, take a look at our list of fall garden chores. And if you’d like spring color before your dahlias bloom, now is the time to plant spring bulbs in fall. For other tender plants, see our guide to overwintering potted plants.