Strawberry plants develop symptoms of winter injury when ice crystals form in crown tissue disrupting cell membranes and functions. Winter injury can occur when temperatures in the crown drop below -12°C (10°F).
Winter injury can cause lethal or sub-lethal damage. Surviving plants may be weakened and/or stunted resulting in low yields. Plants suffering from winter injury are more susceptible to insect and disease damage. The likelihood of winter injury increases when plants are exposed to alternating warm and cold temperatures during the winter season. Freeze thaw cycles can cause soil to heave, breaking plant roots and exposing crowns to the air.
Heavy applications of nitrogen fertilizer in the fall can increase the chances of winter injury to the plants because they don’t harden off or acclimate for winter. Raised beds can also increase the risk of winter injury because cold can penetrate the soil more deeply.
Winter injury can be diagnosed by digging affected plants and cutting lengthwise through the crown. Crown tissues are normally white, however, with mild winter injury brown flecking can be seen throughout the crown. If growing conditions are slow and favourable, strawberry plants can recover from mild winter injury. With more severe damage, crown tissue turns dark brown near the top of the crown and plants rarely recover.
Mulching with hay, straw, leaves or similar materials can reduce the probability of injury. A blanket of unpacked snow provides protection from winter injury, ice however does not.