While blueberry bushes need a chilling period to ensure a good fruit set in the spring, they still need protection from really cold weather, especially in late winter, so that the roots and tender shoots are not damaged. If freezing conditions damage new buds and blossoms, there will be less fruit for that season. Protecting the bushes in the early spring, when new growth emerges, is very important.
Plant blueberry bushes in a location which is protected from winds, since cold winds during the winter can damage the bushes. Planting on a slope or the east side of a house or other building creates warmer conditions during the colder months.
Maintain moist soil during cold months to help protect blueberry bushes from freezing temperatures. Moist soil absorbs more heat during the day and helps to conduct heat toward the surface of the soil, keeping the roots warmer. Water the bushes for one or two days before the first anticipated frost, then water once a week through the winter.
Apply a balanced fertiliser, 12-12-12, throughout the growing season from early spring until the end of August. Fertilizing into the fall or using a food with higher nitrogen (the first number on the bag indicates nitrogen) creates new growth making the bush more susceptible to damage from freezing temperatures.
Add a 2- to 3-inch layer of mulching material the week or two before the first anticipated frost. Using mulch helps to conserve moisture in the soil, creating a warm environment for the blueberry roots, and prevents extreme temperature fluctuations in the soil which can damage the roots. Use shredded bark, straw, peat moss, leaves or grass clippings.
Cover the blueberry bushes with row covers or a polypropylene material when temperatures stay consistently below -6.67 degrees Celsius. Gently drape the covers or material over the bushes in the late afternoon to hold in heat. Only use covers for the bushes during extremely cold periods. You can also use burlap bags or old sheets or blankets.
Do not water the blueberry bushes with a sprinkler.