As I noted on Page 1, generally I receive a frost in my zone 5 garden by early November. One or two weeks after that frost, I begin the process of storing dahlia bulbs for winter. As noted earlier, I usually grow mine in pots, so all I have to do is move the pots inside. When warm weather returns for good, I can bring the pots back outside (always prepared, however, to move them back inside if the weather takes a turn for the worse). I don't need to re-plant them, because I never removed them from their pots.
But let's assume you wish to employ the storage method described in this tutorial. When can you re-plant the dahlia bulbs?
Regardless of whether you live in zone 5, zone 6 or zone 7, there's a simple way to remember when to plant dahlia bulbs: plant after danger of frost has passed in your area. If you don't know when that is in your region, ask an experienced gardener or check with your local county extension. In my zone, you would wait until the Memorial Day decorations go out: the end of May. Although the timing of the last frost date can vary greatly from year to year, gearing your planting to Memorial Day just makes it easier to remember: it is the time when, traditionally, folks have installed tender plants in my area. If the spring has been exceptionally warm, however, make sure your storage area isn't overheating.
Other popular tender plants traditionally installed around Memorial Day in the North include: