This is to reply to the person from Cincinatti, OH. Canas I do not know about. However Dahlias I have grown for years. Answer to your question about digging them up. If it is real cold in the winter or lots of rain and snow in
zone 6, yes should dig your dahlias up after the first frost. You should divide and store them in a root cellar where the temperature will remain between 45 and 50 degrees. Why root cellar?
Because the temperature in a root cellar stays quite consistent. You should store them in crates or boxes and cover the dahlias in bark dust or vermiculite. This will best protect the tubers over the winter.
In a climate where there is lots of snow or winter rain leaving the dahlias in the ground is too risky. There is a good possibility that your dahlias will develop root rot or else freeze. If that happens, your dahlias have gone bye bye.
I hope this answers the question regarding dahlias.
bomar1224@aol.com