5 Simple Steps to Save Your Dahlia Tubers Over the Winter for Next Year's Garden

Dahlias often bloom with the exuberance of favorite annual plants such as zinnias and marigolds. But unlike annual flowers, these plants grow from bulb-like tubers that can regrow into new plants the next year. To ensure your dahlias survive winter, you may have to help them, depending on your growing zone. Here's what you need to know to successfully dig and and store dahlia tubers so you can continue enjoying them year after year.

Are Dahlias Perennial?

Dahlias are native to the mountains of northern Mexico. They are hardy, or perennial, in tropical and warm climates, springing up from the ground each spring. Generally, dahlias are perennial in Zones 8 and above. In Zones 7 and below, dahlia's fleshy roots—called tubers—are killed by cold temperatures.

If you garden in Zone 7 and below, you don't have to say goodbye to your dahlias and begin with fresh tubers next year. Overwinter dahlias by digging them up in late fall and saving them in a frost-free place until it's time to replant in spring.

How to Store Dahlias for Winter

Dahlias can be a bit tricky to dig up and save over the winter. In fact, many cold-region gardeners opt to just grow dahlias as annuals, buying new plants each year. Overwintering dahlias as perennials takes patience, persistence, and a little bit of trial and error.

Moisture is a common cause of overwintering trouble. Too much moisture can cause rot and too little dries out dahlia tubers. Getting the balance of moisture just right is the key. Follow these steps to store your dahlia tubers successfully until you can plant them out again in spring. Moist, ventilated storage is critical to overwintering dahlia tubers.

1. Wait for a Freeze

Allow dahlia foliage to completely die back to the ground in fall before digging the tubers. While a light frost will damage flowers and some foliage, the plant will continue to actively grow. Wait to dig the tubers until a killing freeze zaps all the foliage. For best results, watch the forecast and leave tubers in the ground for a week or more after the killing freeze to allow them to continue maturing. Dig the tubers as soon as low temperatures regularly dip to freezing.

2. Dig Carefully

Dahlia tubers are soft and fleshy and loosely held together by a network of underground stems. Lifting them out of the ground requires some gentleness to avoid damaging them. Use a potato fork or shovel to loosen soil all around the clump, working at least 1 foot away from the main stem. Carefully lift the clump of tubers out of the ground and brush away soil clinging to the individual tubers.

3. Let Tubers Cure

The tubers are very soft when they come out of the ground in fall. Encourage them to harden or cure by spreading them out in a well-ventilated, shaded area for a few days. A covered porch or garage can be a great place to cure dahlias. Make sure to protect them from freezing temperatures.

4. Store Well

Balance moisture and air circulation around your tubers by packing them in a ventilated box, crate, or basket. Place the tubers upside down, allowing plenty of space between the clumps. Cover the tubers with a 4- to 6-inch layer of moist vermiculite or fine wood chips, such as commercially sold pet bedding.

Exactly how wet the vermiculite or wood chips should be is dependent on the humidity in your storage area. Begin by creating a packing material that is less moist. Then, you can easily add water if tubers appear to be drying out.

Store the ventilated box or basket in a garage, basement, or minimally heated place that is between 35 and 50°F. Avoid locations that have hot or cold drafts or are too damp or extremely dry.

5. Check In

Pull back the packing material and check tubers every couple of weeks. If the tubers appear to be dry or shriveling, sprinkle the packing material lightly with water. Get a jump start on the growing season by planting tubers in pots about 4 weeks before the last spring frost date. Grow dahlias in a bright, sunny window or under grow lights and transplant into the garden when all danger of frost has passed.