Question: Is it time to dig and store my dahlias and other summer flowering bulbs? What is the best way to store them? Answer: The ideal time to dig tender, summer flowering bulbs such as dahlias, tuberous begonias, cannas, callas, ranunculus and gladiolus is after the frost has killed the tops, but before it gets cold enough to freeze the bulbs in the ground. We are just about at that point now. Tuberous begonias are the most vulnerable because they are closest to the soil surface.
If you dig carefully, you will usually find smaller bulblets with the larger bulbs, which will develop into full-size bulbs in a year or two. They will not bloom the first year. After digging, cut off the tops leaving an inch or two of stem.
Bulbs can be washed with water or simply brushed to remove dirt. They should be air-dried for a few days in a location where they will not freeze. After drying, stems usually separate easily from the bulbs.
Dahlias with multiple tubers can be divided. Make sure each tuber has an attached growing point. The ideal storage temperature is about 50 degrees.
Bulbs can be stored warmer if they are protected from excessive drying. A fine mesh material such as old nylon stockings will keep them from drying too much. Dry sawdust or vermiculite is even better for keeping the bulbs at the best moisture level.
They can be stored in a refrigerator if there is nothing else that generates humidity. This is also a good time to divide and replant hardy bulbs such as iris and li.