Some varieties of blueberries are very cold hardy while others can suffer in the slightest frost. Winter injury may go unnoticed until the plants begin to develop new leaf buds in the springtime. Planting the correct variety for your climate and protecting your blueberry plant during cold snaps will help ensure healthy growth and an abundance of tasty produce.
There are four main types of blueberry bushes. Rabbiteye blueberries are very susceptible to cold damage and mostly suitable for growing in warm southern climates warmer than U.S. Department of Agriculture plant hardiness zone 7. Lowbush blueberries survive in zones 3 through 6, while highbush varieties are hardy in zones 4 through 11. Half-high blueberries are a cross between the highbush and lowbush varieties. These blueberries grow in climates as cold as zone 3 and can tolerate temperatures as low as minus 30 degrees Fahrenheit.
Frost damage usually occurs when air temperatures drop after the flower buds begin to form on the shrubs. Although blueberry plants may tolerate cold temperatures during dormancy, they lose their ability to withstand frost as they begin to grow in the spring. Brownish, deformed blossoms are often the first symptom of frost damage. Depending on the extent of damage, early frosts may prevent the formation of fruit or may lead to the death of the entire blueberry plant.
Selecting varieties suitable for your climate is the first step in avoiding frost damage in blueberry plants. Avoid planting blueberry plants in low elevations in the landscape. Elevated areas experience warmer temperatures during cool weather while low areas tend to hold in the cold. A layer of mulch over the soil can help insulate the underground roots, while a blanket placed over the plants prior to an expected late-spring frost can help limit possible damage to emerging buds.
Removing the dead and damaged sections of the blueberry plant can help limit the spread of disease. Dead vegetation provides a breeding ground for disease organisms. Pruning off the frozen portions of branches and stems will allow the blueberry plant to direct its energy to producing healthy, new growth. Removing the dead vegetation from the surrounding soil will help cut down on fungal diseases that may affect the health of the blueberry plant.