Dahlia tubers can be dug up and divided during the winter months. The dahlia tubers should be stored in a cool, dry place such as a basement or cellar.
Remove any soil from around their base, using a spade to loosen the earth around them. Then, dig deep enough to make a hole big enough so you can carefully take out the dahlia tuber.
How do you go about digging up dahlia tubers for winter storage?
Trim and clean the dug-up tubers. Gently trim the dead stems off the tubers and break off any large clumps of soil by hand.Wash the remaining dirt off with a hose to reduce the possibility of fungal disease.
The best way to store them is in peat moss, which will only keep them good for about 6 months. A better method is to store them in sawdust or sand and place them in hot water or an icy freezer.