Bonsai, although hardy, do appreciate protection from the worst of the frost and drying winter winds from mid-autumn to late-winter. So now is the time to prepare your storage area or greenhouse. Clean, remove debris and power-wash greenhouses and polytunnels. A protected spot in the garden, cold frame, cold greenhouse or unheated porch can be used for winter storage; do not overprotect. Do not bring trees into the house, unless they are tropical. Bonsai need a dormant period to survive.