Saving dahlias, cannas, etc. over winter:
1. Wait until a frost has killed the leaves and the plant is starting to go dormant before digging out of the ground.
2. Cut off the plants, leaving a few inches of stem coming up from the root. Wash all the soil off and allow them to dry thoroughly.
3. Store in a cardboard box or paper bag with peat moss or dry potting soil to keep roots from drying out too much or being too moist.
4. Store in a cool, dark place but check on the roots from time to time and lightly mist if they start to appear shrivelled.
5. Pot them up indoors in early spring and plant outside again when all risk of frost is gone.