Procedures for storing dahlias and gladiolus are very similar
Lifting dahlia tubers and storing them for planting next spring can be a challenge because they often rot or spoil in storage. After the first frost when the dahlias' foliage turns black, let them adjust to dormancy for a week. Cut back the foliage and stem to within 6 inches of the ground. This makes it easier to see the base of the dahlia and where you will need to spade around the plant.