The NCSU Extension recommends keeping the soil moist, since moist soil absorbs more heat during the day than dry soil and conducts heat to plants at night. Cooperative Extension is based at North Carolina's two land-grant institutions, Blueberries are a hardy type of fruit but still require at least 140 frost-free growing days per season in order to thrive. This design requires 12 sprinklers/acre. You can also use floating row covers on your blueberry, which help to retain heat. Early-season frosts can be especially damaging to blueberry bushes: If flowers are partly open on early-flowering cultivars, a spring frost can injure the open blooms and cause a partial to total loss of fruit yield. Pruning -- Flower buds on short, small-diameter shoots will open and become susceptible to freeze damage sooner than flower buds on larger diameter shoots. Also, the increased soil air will cause the surface layer to be a better insulator which will decrease the amount of heat released from deeper in the soil. However, a very brief time at the critical temperature may damage only the pistil. Other factors to consider include: a) soil drainage (do not plant in a flood-prone or water-stagnant area); b) good aeration; and c) acidic soil high in organic matter. cold hardy and rarely suffer any severe blueberry winter damage Chances are, however, that blueberries and frost are going to come in contact in your garden, especially if you are growing blueberries where they are native in the north eastern U.S. Bushes have nearly 100 percent damaged fruit, and this can quickly become problematic for infection from diseases such as botrytis, which can hurt the crop long term. If a large number of ovules or young seeds are black, the flower or fruit will probably drop. Pruning to a balance of early blooming and later blooming shoots will help insure a crop. Unopened blueberry buds are damaged at 21°F; Blueberry buds that have ruptured are damaged at 25°F; Fully opened flowers are damaged at 29°F; Fully formed blueberries are damaged at 30°F; Use Row Covers and Nursery Foam to Combat the Cold … However, at 40% relative humidity the system should be started at about 37°F to avoid evaporative cooling below 30°F. Preparing the planting ground Plant blueberries during late fall or early spring. For example, the North Carolina State University Extension recommends balancing early and late-season pruning, to make bushes less vulnerable to frost damage of new growth. Blueberry fields will often be as much as 10 to 12°F colder on a radiation frost night than warmer locations such as airports. In some regions, blueberry plants are exposed to frost, but the resulting damage to their flowers depends on a few factors. N.C. commitment to diversity. If only a few are damaged, fruit development usually continues, but the fruit will be later ripening and of smaller size than berries with a larger number of healthy seeds. As new flowers develop, they become increasingly vulnerable to frost damage. Prune off discolored or dead growth with anvil pruners to stimulate new, healthy growth. Blueberries bloom in late winter or early spring in Florida, making the flowers and young fruit highly susceptible to freeze and frost injury. For highbush without adequate frost protection damage is near. Blueberry fields will often be as much as 10 to 12°F colder on a radiation frost night than warmer locations such as airports. Listening to weather reports is not a reliable method of monitoring current temperatures or determining what the low temperature will be in a blueberry field. Commercially manufactured temperature alarms are available or they can be assembled from a refrigeration thermostat and transformer. A&T State University, in all 100 counties and with the Eastern Band of Cherokee Repeated freezing and thawing, or very rapid thawing can be particularly damaging to plants. Most blueberry bushes need some portion of the year for cool-weather dormancy. Until the cold requirement is achieved, an extended period of warm weather usually will not cause floral budbreak. The corolla withers, but usually remains attached. Blueberries (Vaccinium corymbosum) are native to eastern North America and related to azaleas and rhododendrons. When corollas have reached half of their full length, temperatures below 25 to 26°F will kill the complete flowers. All or a portion of the damaged pistil will develop a brown appearance and prevent pollination and fruit set. Causes of frost damage Ground frost occurs when the temperature of the ground falls below freezing point (0ºC/32ºF) and air frost occurs when the temperature of the air falls below freezing point. If the soil has been cultivated, the surface layer will contain more air and less water. Varieties that continue to grow late in the season, however, are more susceptible to late-season frost injury than varieties that stop growing earlier in the season. The plot of temperature and humidity as the night progresses on the hygrothermograph chart aids in making the best possible management decisions. During the winter, dormant flower buds of highbush blueberries will survive temperatures as low as -20 to -30°F while the less hardy rabbiteye (V. ashei Reade) have survived -10°F but are often damaged below 0°F. If a frost or freeze occurs, there will still be some later fruit for a partial crop. Thermometers in warm, cold and average locations in the field should be checked in addition to the hygrothermograph to determine differences across the farm. Immediately after corolla drop and before the berry begins to swell is the most sensitive stage. Healthy ovules are plump and white, but become black with cold injury. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status. — Read our Blueberries and frost are not a desirable combination, but understanding blueberry temperature tolerance and how to assess damage from frost can help you protect your blueberry bushes as the days turn colder. Maintaining a moist surface on peat and muck soils is especially important. Excess water for extended periods must be avoided to prevent flooding or phytophthora root rot damage. Many of the official temperatures reported on radio or television are taken at airport locations. The U.S. Department of Agriculture hardiness zones for blueberry plants depend on the variety; according to the Farmer's Almanac blueberry bushes generally do well in zones 3 through 9. Frost damage to blueberry plants is generally most evident when their flowers open fully. And half-high varieties are hybrids of highbush and lowbush varieties. With sprinkler irrigation for frost control, the system must be started at a higher temperature when humidity is low to compensate for the evaporative cooling that will occur as the first water strikes the bushes.