What do you do when dahlias have finished flowering?Updated 14 days ago

Dahlias usually continue flowering until the first frost. If they have stopped flowering before the first frost, anytime between September and December the tuber can be lifted from the soil. If they are still flowering well through autumn, you can leave it as late as mid November. 

After lifting, the stem should be cut off 2-5cm from the tuber and the tuber should be cleaned, dried for 1-2 weeks and stored in frost-free conditions for winter. For storage, rest the tubers in trays or shallow boxes with a light scattering of dry compost and keep them in a dry, frost-free place like a cool greenhouse, shed or garage for winter. Be sure to label them so that you know which variety is which. There is no need to water them at all while in storage. You can replant them in spring between March and early May.