Dahlias are beautiful flowers that bloom in late summer and add luster to the landscape with their foliage in various shades of green and blooms that range from petite pom-poms to flowers the size of dinner plates, in an entire rainbow of colors. Here are some tips on what to do with dahlias in the fall:
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After a hard frost, cut the plant back to about 6 inches from the ground: When the dahlia foliage and stalks die back after a hard frost, cut the plant back to about 6 inches from the ground. This will help the tuberous root system to live on to produce a stunning display year after year.
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Let them go through a freeze: Dahlias need to feel a freeze in order to properly go dormant and cure their tubers. When you let your dahlias freeze in the fall, that tells the plant, “OK, it’s time to go dormant for the winter.” The stalks turn black, their skins are thickening up underground and they are preparing themselves for winter. Dahlias dug too early have thin skins and typically do not survive the winter.
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Store them for winter: If you live in an area where the freeze reaches a depth of 4-6" or more, then leaving your dahlias in the ground is not an option. In many climates, dahlias must be dug and stored as tubers cannot freeze. In warmer/mild states, including the Pacific Northwest, you may try leaving the dahlias in the ground over the winter. It is never a guarantee, but many customers find that this is a more successful route compared to digging and storing. If you do not dig in the fall, but would still like to divide your dahlias, divide them in the spring.
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Check on your dahlias periodically through the winter: Check on your dahlias periodically through the winter. If the storage conditions are too moist, you may get some mushy tubers. Remove them and increase the ventilation to reduce moisture levels. If the tubers are wrinkled and dry, mist them or add some damp growing mix to help them rehydrate.
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Label your plants: Start by labeling your plants with survey tape before you get a frost so you can still see the flowers and evaluate which plants you want to keep. Save only the plants that are strong and healthy, and that really impressed you.
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Divide and replant in the spring: In late winter or very early spring, pull out your dahlias and divide them. Then plant them back out in the spring. They need a minimum of 3 months of rest between growing seasons.
In summary, after a hard frost, cut the plant back to about 6 inches from the ground, let them go through a freeze, store them for winter, check on them periodically, label your plants, and divide and replant in the spring.
