Strawberry plants are perennials designed to survive the winter and produce fruit for many years, but they require preparation to thrive after the cold season. The goal of winter care, known as winterizing, is to protect the crown and roots from extreme cold and repeated freezing and thawing cycles. This process is important in climates where temperatures frequently drop below freezing. Successful winterizing ensures the delicate flower buds, formed in the previous fall, remain undamaged, leading to a robust spring harvest.
Preparing the Plants for Dormancy
Preparation for winter begins in late fall, after the plants have stopped active growth and before the first hard freeze. The initial step involves a thorough cleanup of the strawberry patch to reduce the risk of disease overwintering. Remove any old, dead, or diseased foliage, as this debris can harbor pests and fungal spores until spring.
Clearing the area of weeds and other garden waste removes potential shelter for insects and pathogens. For June-bearing varieties, a light pruning of the leaves, leaving the crown exposed, encourages full dormancy. As temperatures drop, gradually reduce watering. Ensure the soil remains slightly damp but never waterlogged, as excess moisture can lead to crown rot during dormancy.
Insulating Against Cold and Freeze Damage
The primary protective measure involves applying a thick layer of insulating mulch over the dormant plants. This layer is applied to maintain a consistently cold soil temperature rather than keeping the plants warm. The insulation shields the crowns from repeated freezing and thawing cycles. These cycles cause “heaving,” which pushes the plants out of the ground and exposes their roots to the air and cold.
Timing the application is precise: wait until the plants have experienced a few hard frosts and the soil temperature is consistently below 40°F, but before the ground freezes solid. Applying the mulch too early prevents the plants from fully hardening off for winter. Clean straw is the most recommended material due to its airy structure, which traps insulating pockets of air while allowing moisture to escape, preventing rot.
A layer of straw four to six inches deep should be spread loosely over the entire patch, completely covering the plant crowns. Other options, like pine needles or shredded leaves, can also be used, but avoid materials like hay, which often contains weed seeds. The loose layer will compress over the winter to a final protective depth of two to four inches, providing a buffer against temperature fluctuations.
Specialized Care for Containers and Everbearers
Strawberry plants grown in containers require different winter protection because their roots lack the insulating mass of the surrounding earth. The container walls expose the root zone to colder temperatures, making the plants vulnerable to freezing solid. Leaving pots above ground in cold climates risks plant death when temperatures fall below 20°F.
The most effective method is to move the containers to a sheltered, unheated location, such as a cold frame, garage, or shed, where temperatures remain cold but consistently above freezing. If moving them is not possible, the pots can be buried into the ground, flush with the soil surface, and covered with four to six inches of straw mulch.
Everbearing and Day-Neutral Varieties
Everbearing and day-neutral varieties produce fruit throughout the season and have a different growth habit than June-bearing types. While they need winter protection, some gardeners in very cold zones treat them as annuals and replant each spring. They may also require a heavier fall pruning to encourage more vigorous spring growth.
Reawakening Plants in Early Spring
As late winter transitions into spring, the protective mulch layer must be removed to allow the plants to resume growth. The time for removal is dictated by the soil temperature, typically when new green growth appears beneath the straw or when the danger of a severe hard frost has passed. Begin the process when the soil temperature reaches about 40°F.
The mulch should not be removed all at once, as the new growth needs time to acclimate to the brighter light and cooler air. Initially, pull back about half of the straw layer, leaving a light covering over the crowns for continued protection. The remaining straw can be moved to the pathways between the rows to act as a weed barrier and to keep the developing berries clean later in the season. After the plants are fully exposed, an initial spring feeding with a balanced, slow-release fertilizer supports the emerging foliage and prepares the plants for the fruiting season.