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How to Overwinter Dahlias
Dahlias are a beautiful summer and fall bloom, but they need to be brought inside and protected during winter if you hope to enjoy them for years to come. This comprehensive guide covers all you need to know about how to overwinter dahlias.
While dahlias can be overwintered in the ground in the south, they can’t make it through winter anywhere here in the northeast. While you can grow dahlias as an annual, it can get expensive to do so. Overwintering dahlia tubers as part of your garden winterization process allows you to enjoy the same ones year after year, and it isn’t very difficult.
There are two common ways to overwinter dahlias, alone as tubers and in containers.
Overwintering Dahlias in Pots
If your dahlias are already in a mobile container, you can just bring the whole pot indoors for the winter. Leave it outside for an initial light frost to force dormancy, then prune the stem back to about 4 inches above the soil. Keep the pots in a cool, dark place that’s dry and doesn’t get below 40 degrees, like a root cellar, basement, or garage. Don’t water the pot.
When you’re near your last frost date, bring the pot out of storage and place it in a warm, sunny location. Give it a cup or two of water and watch for growth before watering more. Once all threat of frost has passed, you can set the pot back outside.
How to Store Dahlia Tubers Over Winter
If you have different types of dahlias, label them before the first frost so you’ll know what they are. If time allows, leave the tubers in the ground until one to two weeks after your first frost, which forces dormancy and strengthens the tubers by adding nutrients. Cut the stem off to about 3 inches off the ground and move your label if necessary.
Leaving about a foot of space away from the stem, start digging up the tuber with a shovel. The tubers can be large and deep. Work slowly and carefully to avoid harming them. Discard any unhealthy or cut tubers.
Brush excess dirt off by hand, and leave the tubers out to try in a frost-free location for several days. You can hang them in an area with indirect light with twine for a few weeks to cure if you like. Once dry, you can either store them as is or divide them, following the directions listed later on in this post.
Storage Methods
You can store your tubers in a variety of ways, including containers, cardboard or plastic boxes, and even paper or black plastic trash bags. Keep lightly dampened potting soil, sawdust, peat moss, or vermiculite around them. Some have even tried using plastic wrap around each tuber.
Unlike other bulbs, dahlias do need a small amount of moisture to stay alive, but it’s important not to give them too much or they will rot. This tricky balance can make dahlia storage difficult, and you should expect to lose a portion of your dahlias the first year or two as you learn what methods work for you.
Keep the humidity of your storage area in mind. If you’re keeping the tubers in a very dry location, go with containers and plastic options that can be covered to keep some moisture in. When it’s at all humid, go with something that can breathe, like a cardboard box, and keep it open, with a breathable paper or cloth over top to keep the light out. If you’re concerned about rotting, you can roll the tubers in sulfur powder.
Place the container, box, or bag in a cool and dark area that stays between 40 and 50 degrees, like a root cellar, basement, or garage. Wherever you keep them, the tubers should never get below freezing.
Check on the tubers every once in a while to make sure they aren’t getting too damp or dry. For rot, remove the affected tubers and keep the rest in better ventilated conditions. If they’re dry and shriveling up, dampen the medium they’re sitting in.
Spring Care
When there’s no more chance of frost outside and the ground is around 60 degrees, replant healthy tubers. If you have a short growing season, you can start them indoors in April near a sunny window. Either way, soak the tubers in warm water for a bit to speed up growth. You can replant them as-is or follow the tutorial listed below to split them and add to your collection.
Avoid overwatering them immediately after planting. You should see growth in your garden after a week or two.
Dividing Dahlia Tubers
You can do this in the fall before storage or in spring before planting. Either way, get rid of any tubers that seem unhealthy or dead. Each section needs to have an “eye” or it will not grow, so split them based on that. If you can’t find the eye, either wait until spring when they start to sprout or just halve or quarter a large tuber, leaving some of the stem.
This tutorial will you show you how to divide them most effectively:
FAQs About How to Overwinter Dahlias
Can dahlias survive winter in the ground?
Only in zones 8 and higher. Dahlias cannot be overwintered in the ground anywhere in the northeast.
When should I dig up and store my dahlias for the winter?
It’s best to dig them up and begin preparing for overwintering shortly after the first frost. You can dig them up before the first frost if you need too, but leave them as long as possible. You can also leave them in the ground for a while after your first frost, but always dig them up before a very hard frost (around 25 degrees or less) and well before the ground freezes. If the ground freezes, the tubers will die.
Can you leave dahlias in pots over winter?
Yes, you can just cut back the stem and bring the pot inside for the winter.
Can I store dahlias in the garage or basement during winter?
Yes, an unheated garage or basement is ideal for dahlias provided they never get below freezing.
What temperature do you store dahlia tubers over winter?
Keep dahlia tubers between 40 and 50 degrees throughout winter.
How much water do dahlias need during the winter?
Dahlias need very little water during the winter. Give them a light misting once in a while to make sure the tubers don’t dry out completely.
How do I bring my dahlias out of dormancy?
Dahlias can be brought out of dormancy by soaking them in warm water. They can then be planted either in the ground or in a pot.
When can I plant my dahlias back in the ground?
Plant dahlias back in the ground once all threat of frost has passed and the ground reaches 60 degrees.
What are some common problems that people have when overwintering dahlias?
The most common problems are the tubers either drying out or rotting. You can prevent both by frequently checking on the tubers throughout the winter and either misting them or drying them out as necessary.
Have Success Winterizing Your Dahlias!
With these tips, you should now know how to overwinter dahlias, both as tubers and in pots. Play around with the methods to find what works best for your dahlias and storage conditions.
You may also be interested in posts on overwintering begonias and overwintering geraniums.
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