Strawberry plants are hardy perennials, but when grown in containers, their roots lose the natural insulation provided by the surrounding earth. This lack of protection means the entire root ball is highly susceptible to freezing solid, which can kill the plant or significantly reduce next season’s fruit production. Winterizing is the process of safely guiding the strawberry crown and roots into a necessary dormant period to ensure they survive the cold and are ready to produce fruit the following spring. Protecting these potted plants is a matter of precise timing and insulation techniques.
Preparing Plants for Winter Dormancy
The preparation process should begin in late fall, waiting until after the plants have experienced a few light frosts, which signals the natural onset of dormancy. This period, usually in November or early December, is when temperatures consistently drop into the low 20s Fahrenheit, causing the plant’s foliage to start browning and shriveling. Waiting for this natural cue ensures the plant has properly “hardened off” by accumulating necessary sugars in its tissues to resist freezing.
Once the plants are entering dormancy, prune away old foliage and runners. Use clean, sharp shears to cut back the leaves to about one to two inches above the plant’s central crown, the point from which new growth emerges. Removing this old growth prevents potential fungal diseases or mold from developing during winter storage. Finally, significantly reduce watering; the soil should be kept slightly moist, not saturated, to prevent root rot before the pots are moved to their final winter location.
Choosing the Right Winter Storage Location
The location chosen for winter storage must maintain a consistently cool temperature, protecting the plants from the harshest freezes while preventing them from waking up too early. The ideal temperature range for maintaining dormancy is between 20°F and 45°F. Placing pots in a heated garage or basement is not recommended, as the warmth may trick the plants into breaking dormancy, leading to tender new growth that will die when exposed to cold air.
One effective strategy is to move the pots into an unheated shed, garage, or cold frame, especially in regions with severe winters. Grouping the pots tightly together increases their collective thermal mass, which helps buffer temperature fluctuations. For insulation, wrap the pots in materials like burlap, old blankets, or bubble wrap to provide protection against cold air exposure.
Sinking Pots Outdoors
Alternatively, potted strawberries can be insulated outdoors by sinking them into the ground or a trench. Dig a hole deep enough for the entire pot to sit flush with the soil surface, or arrange them tightly in a prepared trench. Once the pots are in place, backfill the gaps with native soil or mulch to eliminate air pockets and provide insulation to the container walls.
Applying Mulch Protection
After the pots are buried or grouped, cover the crowns and the surrounding soil with a thick layer of loose mulch, such as straw or pine needles. This mulch should be spread six to eight inches deep over the entire area to shield the dormant crowns from repeated freezing and thawing cycles.
Dormancy Care and Spring Revival
Even while dormant, potted strawberry plants require minimal attention to survive the winter and prevent desiccation. The primary concern is ensuring the root ball does not dry out completely, which can be a risk, especially in sheltered indoor locations. Check the soil moisture monthly, or more frequently during unexpected warm spells, and apply a light watering only if the soil is bone dry several inches down.
Keep the soil lightly damp, not saturated, as excess moisture in cold conditions can quickly lead to root rot or mold formation. If storing plants in an unheated garage or shed, occasionally check the pots for signs of mold or pest activity. Maintaining consistent, cool temperatures is important, as fluctuations can deplete the plant’s stored energy reserves.
The end of winter signals the time for a gradual transition back to active growth to prevent the plants from experiencing shock. After the last expected hard frost has passed and when daytime temperatures consistently stay above 30°F, you can begin to remove the protective mulch or insulation. If the plants were stored indoors, slowly introduce them to outdoor conditions, starting with a few hours a day in a shaded location. This gradual acclimatization helps prevent leaf scorch and prepares the plant for full sun. Once permanently moved back to their growing location, resume a normal watering and feeding schedule to stimulate new growth and prepare the plants for flowering.