Strawberry plants are perennials with significant natural cold tolerance, especially when fully dormant. Whether strawberries can handle frost depends heavily on the plant’s stage of growth, as vulnerability increases dramatically once new spring growth begins. Understanding this relationship is necessary for a successful harvest. A sudden drop in temperature in early spring, when plants emerge from winter rest, can destroy potential fruit even if the plant survives the cold event.
Vulnerability by Growth Stage
The strawberry plant’s hardiness changes throughout the year, centered on the crown, the short, compressed stem structure located at the soil line. When dormant in winter, the crown is remarkably tough and can survive temperatures far below freezing, often protected by snow or mulch. This overwintering stage represents the plant’s maximum cold tolerance.
Once the plant breaks dormancy and produces new leaves, its resistance to cold decreases significantly. New leaf and runner growth contain high water content, making them susceptible to ice crystal formation. While damaged leaves are often cosmetic and the plant can recover, frost at this stage signals that more sensitive reproductive structures are soon at risk.
The highest risk of damage occurs when plants are in the reproductive stage, specifically when blossoms are open. The delicate floral structures, which contain the potential fruit, are the most vulnerable parts of the plant. Since strawberries are one of the first fruits to bloom in spring, they frequently face late-season cold snaps.
Developing fruit is also susceptible to cold injury, though slightly less so than open flowers. Green or ripe berries have high water content and can suffer internal damage from freezing, leading to misshapen or soft spots. The plant produces flowers over several weeks, which ensures that not all potential fruit is lost in a single frost event.
Critical Temperature Danger Zones
The temperature at which a strawberry plant suffers injury is directly tied to its stage of development. The most cold-tolerant part is the dormant crown, which can survive temperatures as low as 10°F (-12°C) when properly mulched. This tolerance allows the plant to survive harsh winters, but this hardiness disappears quickly as spring growth emerges.
Flower buds that have emerged from the crown but remain tightly closed can withstand temperatures down to approximately 22°F (-5.5°C). As the bud develops into the “popcorn” stage (petals visible but closed), the critical temperature rises to around 26°F (-3.3°C). The plant’s highest vulnerability is reached when blossoms are fully open, with damage occurring at 30°F (-1.1°C) or lower.
Young green fruit is slightly more tolerant than an open flower, with a critical temperature of approximately 28°F (-2.2°C). These thresholds apply to the plant tissue itself and may be slightly lower than the air temperature measured at eye-level. The duration of the cold event also impacts the severity of the damage, as longer exposure causes more injury at a given temperature.
Practical Frost Protection Strategies
The most reliable strategy for protecting strawberries from predicted frost is using physical barriers, such as row covers or blankets. A floating fabric row cover, especially a heavier material, can raise the temperature underneath by several degrees, providing an insulating layer that traps the day’s heat. These covers should be applied in the late afternoon before the expected freeze to capture warmth. They must be kept from directly touching the blossoms, as contact can transfer cold and cause localized damage.
Another highly effective method, widely used commercially, is overhead irrigation. This technique involves continuously sprinkling water over the plants throughout the cold period until temperatures rise above freezing. As the water freezes, it releases latent heat, which keeps the temperature of the ice-encased plant parts near 32°F (0°C), insulating the delicate tissues. It is necessary to continue application until the ice begins to melt naturally, as stopping too early can cause more harm.
For container-grown strawberries, relocating the pots to a sheltered area like a garage or porch is a straightforward solution. For plants in the ground, applying a heavy layer of straw or pine needle mulch in the fall is a preventative measure for winter survival. In spring, moving the mulch to cover emerging plants during a short-term frost offers temporary protection to the blossoms. Keeping the soil moist before a freeze also helps, as wet soil retains and releases more heat than dry soil.
Post-Frost Assessment and Care
After a frost event, assess the damage to determine the necessary recovery steps. The most critical check is on the blossoms, the primary target of cold injury. To check for damage, gently slice open a few affected flowers and look at the center pistil structure. A healthy pistil will be bright yellow or green, indicating intact reproductive tissue. If the center of the blossom has turned black or dark brown, the pistil has been killed by the cold, and that flower will not produce marketable fruit.
Damage to the leaves and runners is generally cosmetic, often appearing as water-soaked spots that turn brown and shriveled. However, the plant usually recovers from this foliage injury.
To encourage recovery and a subsequent yield, prune away any dead or blackened blossoms. This allows the plant to redirect energy to new, healthy flower buds. Follow-up care should focus on maintaining consistent soil moisture and providing balanced nutrition. Since strawberries produce flowers over an extended period, the loss of the first wave of buds does not mean the entire harvest is lost, and subsequent blooms can still yield a crop.