I don’t know any gardeners who casually grow dahlias. Their fireworks riot of color has an intoxicating effect. You may start with one dahlia, but before you know it you have torn out the roses, planted five hundred tubers and (in at least one documented case), transformed an old tennis court into a fenced garden to make room for more flowers.
But dahlia devotees pay a price. In cold climates (read: the ground freezes), dahlia tubers need to come out of the garden if they are to survive the winter. Dig them up and store them in the basement, garage, or a protected shed—and dahlias will reward you next summer with more enormous puffball blooms. It’s worth the effort.
Here are step-by-step instructions for how to store dahlia tubers in winter:
Photography by Mimi Giboin for Gardenista.
Step 1: Wait for the First Frost
Flowers will wilt, leaves will blacken, and dahlia stems will die back after the first frost; you’ll know it’s time to store tubers in a safe spot for the winter.
Step 2: Dig Up Dahlias
To dig up, first cut back stalks to a height of 2 to 3 inches. Then start about a foot away from the plant, loosening soil all around the roots and digging deep enough (18 to 24 inches) to get your shovel underneath the dahlia to tease it out of the ground.
Dig up one clump of tubers at a time and be gentle; the tubers are fragile and break apart easily.
Step 3: Rinse Off Dirt
4. Trim Tubers
5. Divide Dahlias
If you have some very large clumps, you may want to divide dahlias before storing them for the winter. After you rise away soil, examine tubers to see if they’ve ready to be divided.
A healthy division will spawn its own clump of tubers after you plant it next year.
6. Store Dahlias in a Dry, Protected Spot
Return tubers to the garden in late spring, after the last frost date. (Dahlias like heat, dry feet, and lots of sun.)
Finally, get more ideas on how to successfully plant, grow, and care for dahlia with our Dahlia: A Field Guide.
Interested in other bulbs and tubers for your garden or indoor space? Get more ideas on how to plant, grow, and care for various bulbs and tubers with our Bulbs & Tubers: A Field Guide.
N.B.: To tour a dahlia garden in bloom, see Dahlia Fever in San Francisco. And don’t miss the sleuths of Dahlia Detectives: 7 Mysterious Heirlooms from an Earlier Century.