Don't Ditch Those Dahlias: Easy Tips for Winter Storage

If you've fallen in love with dahlias like I have, you know their gorgeous late-season blooms are worth the extra effort. In colder climates, you'll need to properly dig and store the tubers to enjoy them again next year. For tips on getting the most out of your dahlias during the growing season, check out The Dirt on Dahlias article. Once your plants have finished blooming, here's how I handle the digging, dividing, and storing to keep those tubers healthy through winter. It might seem intimidating at first, but with a bit of practice (and patience), it becomes just another part of the gardening rhythm.

Dahlias need to be in the ground for at least 120 days to produce mature tubers for storage. It is unnecessary to wait for the first frost to dig up tubers, but I wait until after the frost to enjoy every single bloom, typically between the second and third week of October in USDA Hardiness Zone 5b. 

Our climate is not conducive to leaving them in the ground, but I have inadvertently left some in the ground that have been in protected areas, like close to the house, and they have survived. Heavy freezing and winter rains can promote rotting, especially in USDA Hardiness Zones 6 and lower. 

First, before digging, I cut the stalk down to where I can carry the clump. A pitchfork works well to remove the dahlia tuber clumps. Ideally, the soil can be shaken off the tubers, but I am not lucky with my soil. I use the hose to get the excess soil off; even with that, there is still soil between the tubers. 

I choose to divide my tubers in the fall. They are more manageable to cut in the fall, but the eyes are more visible in the spring. I lose some eyes (potential plants) this way, but the tubers are easier to store. Sometimes tubers may look healthy and not have any eyes. This occurrence is known as a blind tuber. If storing in a clump, it is recommended not to wash the soil off, but this does require more storage space.

To begin the process, cut the stalk off to the tubers, turn over, and divide, knowing that viable tubers are always attached to the old stock. Each tuber must have a neck and a crown to get a viable eye. Necks that are less than the diameter of a pencil will probably dry out by spring. I use loppers to cut the stalk, a sturdy hunting knife to cut the tuber crown from the stalk, and scissors to trim the roots. Not trimming the roots can lead to too much moisture being retained. I watched many videos before I attempted this in my first year. I then sprayed the tubers to remove the excess soil and let them dry for four or five days out of the sun. I originally let them dry for the recommended 24-48 hours, but I found that they needed more time to dry, or they were more prone to rot. 

Tubers must be stored somewhere they cannot freeze and off of cement floors. My storage area usually ranges from 40°F to 50°F, with some minor variability. A few times, when air temperatures have been around 0°F, I have moved the containers into a temporary warmer area.

I use plastic bins with lids and drill holes in the sides for air flow. I layer the tubers, using cedar shavings, and do not click the lid shut. After a few weeks, I check, and if the shavings are moist to the touch, I change them. They are usually good for the rest of the season. During that first month, I typically have an issue with too much moisture.

On the other hand, if your medium seems too dry, a spritz of water may be necessary, which I have never needed to do. Humidity levels in the storage area come into play. It is not recommended to use cardboard boxes, newspapers, or paper bags due to wicking up too much moisture. There are other storage media available that work best with certain humidity levels. A lot of trial and error will occur during your first season, but relax and enjoy the beauty of dahlias.

Storing dahlias can feel a little tricky at first, but it gets easier with experience. Stay flexible, pay attention to what works in your space, and don’t stress if a few tubers don’t make it—most of us have been there. With the proper storage setup, you’ll be rewarded with healthy tubers and big, beautiful blooms next summer, which makes it all worth it.