What to do with your dahlias in cold winter areas
Where winters are cold or wet, it's best to remove dahlia tubers from the ground and store them in a frost-free place until spring.
1. In late fall, when foliage has withered, cut back flower stalks to 4-inch stubs. Dig a 2-foot-diameter ring around each plant.
2. Gently lift tubers from the ground, shake or hose off soil, and let them dry in the sun for a few hours. Tag them, or use an indelible pen to write the variety name directly on each tuber.
3. Fill nursery flats or wood boxes with dry peat moss, sawdust, or wood shavings. Bury the tubers in a single layer. Store in a cool (40°-50°), dry place until spring planting time.