Obtain one or several sturdy cardboard boxes that have lids. Another option is foam coolers.
Cover the bottom of the box with at least 10 newspaper pages. Some gardeners use course vermiculite or sand along with the newspapers when storing divided tubers. Tubers stored with soil will not need these.
Place the dahlias in the box. Space divided tubers so they don’t touch to prevent spreading rot, if this occurs during storage.
Add another layer of newspaper on top of the dahlias tubers. Continue adding more layers or tubers and newspapers, if you are storing several tubers in one large box. Always end with a top layer of newspaper.
Place the cover on top of the box or fold the top flaps to seal the box.
Keep the box in a location with a temperature range between 40 and 55 degrees Fahrenheit.