If you live in USDA Hardiness zones 8 or warmer, you can leave your tubers in the ground over the winter. After a frost, cut back the foliage almost to the ground, then cover with plastic, straw or other organic mulch to prevent water from going down inside the hollow stem and rotting the tuber, says Hunter. Remove the mulch in the spring.
In colder areas of the country if you’d like to save the tubers to replant next spring, let the foliage die back after a hard frost, cut it to the ground, then use a digging fork to lift the tubers up out of the soil. Brush off most of the dirt, and let the tubers sit out for 48 hours or more in a cool, covered location to dry. Once dry, wrap in newspaper, cedar shavings or cat litter to keep the tuber protected over the winter. Store in an unheated location that remains around 40 to 45 degrees.
Don’t be disappointed if your tubers look shriveled and funky next spring. “It’s not the easiest task to overwinter these tubers successfully, so don’t feel bad if you grow dahlias only as annuals,” says Hunter. If that’s the case, treat yourself to some new tubers next year.
