How to Overwinter Strawberries in a Cold Greenhouse

Prepare the strawberry plants for overwintering. Remove the foliage from the strawberry plants. Be careful not to cut so far down that you damage the crown. Leave about 4 inches of the foliage stems attached. Transplant strawberries from terracotta pots into plastic pots. Terracotta pots will absorb moisture and crack under cold-weather conditions, but plastic pots will not.

Insulate the walls of the greenhouse to protect the strawberries from cold damage. Attach sheets of bubble wrap or polythene to the walls of the greenhouse. These materials can be found at garden centers or home-improvement stores. Place the potted strawberries inside the greenhouse, away from the walls.

Water the dormant strawberry plants sparingly during the winter months. Check the soil weekly to determine if water is needed. Keep the soil damp so the plants do not dry out. Avoid overwatering, as this will cause the plants to develop mold and the roots to die. The soil should never be wet.

Check the temperature of the greenhouse on sunny winter days, as the sunlight can heat the greenhouse to damaging temperatures. Open a door or vent if the temperature is above 40 degrees Fahrenheit to cool the interior of the greenhouse. Move the strawberries out of direct contact with the cool air.

Move the strawberry pots outside during the day in the early spring to begin acclimating them to outdoor weather. Return the pots inside the greenhouse during the night until the last frost has occurred.