Strawberry plants are perennial, but their crowns—the central growing points—are susceptible to damage from harsh winter conditions. Overwintering protects these crowns primarily from the destructive freeze-thaw cycles common in temperate climates. The repeated expansion and contraction of the soil can heave the plant out of the ground, leading to root damage and death. This insulation also helps prevent the dehydration of plant tissues during periods of low moisture and high wind.
Preparing Strawberry Beds for Dormancy
Preparing the strawberry patch begins in late autumn, typically after the final harvest or when growth slows significantly. The first step involves thoroughly cleaning the bed by removing old foliage, weeds, and any runners. Removing this debris reduces the likelihood of disease pathogens and insect pests surviving the winter.
For June-bearing varieties, cut back the leaves (renovation), leaving only about one inch of foliage above the crown. This trimming directs the plant’s energy toward developing strong root systems and buds for the following year’s fruit production. Ensure the crowns are fully hydrated before the ground solidifies, as adequate moisture increases their resilience to cold-weather desiccation.
Applying and Maintaining Winter Protection
The application of winter protection must be precisely timed to avoid smothering the plants prematurely or leaving them exposed too long. Wait until the soil surface has frozen solid, which usually corresponds to air temperatures consistently dipping to around 20°F. Applying the covering too early traps warmth and moisture, potentially encouraging fungal growth or causing the plants to break dormancy during a warm spell.
Clean, seedless straw is the most effective material because its hollow stems provide excellent insulation without compacting heavily around the crowns. Pine needles can also serve a similar purpose. Apply the material loosely to a depth of four to six inches over the entire bed, aiming for a compressed depth of two to three inches once settled.
This thick layer acts as a thermal blanket, insulating the ground and maintaining a steady, cold temperature around the plant roots. The primary function is to prevent the soil from warming up and refreezing repeatedly. Periodically check the patch throughout the winter, especially after heavy winds, to ensure the protective layer has not been blown away.
Overwintering Container-Grown Strawberries
Strawberries grown in containers face a greater challenge because their root systems lack the thermal buffer of the surrounding earth. The thin walls of the container allow the soil temperature to fluctuate rapidly and freeze completely, which can quickly kill the roots.
One effective strategy is to move the containers into an unheated but sheltered location, such as a shed or garage, once the plants are dormant. The temperature in this space should remain consistently below 40°F to keep the plants dormant but above 20°F to prevent root death.
Alternatively, the pots can be grouped closely together and surrounded by insulating materials like straw bales or burlap, focusing on insulating the exterior walls of the container. A third method involves burying the containers directly into the ground, up to the rim, utilizing the earth’s natural thermal mass to stabilize the root zone temperature. Regardless of the method chosen, container plants should receive one final, thorough watering before being tucked away for the winter.
The Spring Transition
The transition out of winter protection must be timed carefully in the spring. Begin the process once the threat of severe hard freezes has passed, usually when daytime temperatures consistently hover above 40°F. Waiting too long will cause the plants to etiolate—develop pale, weak growth—as they try to push through the heavy covering in the absence of sunlight.
The protective layer should be removed gradually, starting by lightly raking off the majority of the material on a cloudy day to prevent sun scald. Leave a thin layer, approximately one inch deep, of the straw or pine needles between the rows. This residual material acts as a moisture-retaining mulch and helps suppress early season weeds.
Once the plants are fully uncovered and new green growth is apparent, apply a light application of a balanced, slow-release fertilizer. This feeding supports the plants as they wake from dormancy and begin the vigorous growth phase necessary for flower and fruit development.