Key Points Digging and storing dahlia tubers lets you enjoy the same beautiful blooms every year, even in cold regions. Dahlias are typically propagated by tubers, and these tubers are only cold-hardy in zones 8 and above—so they will struggle in colder regions. "You'll know when the dahlias are ready to dig up when the first hard frost blackens the foliage," says horticulturist Kate Walz. Use a pitchfork to loosen the soil around the plant, and then dig deep to lift the clump of tubers. How to StoreThere are many different ways to store dahlia tubers; it may take some trial and error to find the method that works best for you.