How to Grow Blueberries in Washington

The ideal place to grow blueberries (Vaccinium spp.) is in a climate where summers are not too hot and winters are not too cold. Coastal Washington fits that bill, and growing blueberries in the state -- at least, the part of it that's west of the Cascades -- is not difficult at all.

Many varieties of blueberry are well adapted to the growing conditions of western Washington, those parts of the state in U.S. Department of Agriculture plant hardiness zone 8, and the state is one of the leading commercial producers of blueberries in the country. Most blueberry varieties do best when winters are mild, however, and they're vulnerable to potentially fatal frost damage where winter cold is severe. Growing blueberries east of the Cascades or in parts of northern Washington, in USDA zones 6 and 7, is difficult because of relatively harsh winter temperatures and short growing seasons. With care and protection from the cold, some varieties of northern highbush blueberries (Vaccinium corymbosum) may be able to tolerate the eastern Washington climate.

Blueberries need well-drained, acidic soil with a pH level between 4.5 and 5.5. If your soil's pH level is too high, add 2 pounds of sulfur per 100 square feet, mixing it into the top 8 inches of soil, to lower the soil's pH by one point. Adding peat moss mixed with an acidic compost can also help bring the soil to the proper pH level. If the pH of your soil is extremely high, consider planting blueberries in raised beds filled with a mix consisting of 50 percent peat moss, 40 percent bark mulch and 10 percent sand. Test the soil's pH annually, and amend the soil to correct the level as necessary.

Blueberries like full sun, although in locations subject to hot summer sun, they may appreciate some light afternoon shade. Exposed areas that are especially vulnerable to late-season frosts are not ideal, but neither are unusually warm, sheltered locations, such as on the sunny side of buildings or walls. Blueberries planted there might be encouraged to bloom early, making their buds and flowers susceptible to cold damage.

Blueberries are vulnerable to fungal infections, such as botrytis and mummy berry, that attack the plant's flowers and fruits. The best method of control for these infections is the quick removal and destruction of infected tissue and the improvement of air circulation around the plants so leaves, stems and fruits don't stay wet for prolonged periods of time.

Most varieties of northern highbush blueberries and lowbush blueberries (Vaccinium angustifolium) perform well in the coastal regions of Washington, in USDA zone 8. Southern highbush blueberries, which are hybrids of northern highbush and Florida evergreen blueberries (Vaccinium darrowii), are sensitive to cold damage and do not usually do well in Washington. Rabbiteye blueberries (Vaccinium virgatum) are native to the southeastern part of the country, and although they may be able to handle the USDA zone 8 conditions in western Washington, they may struggle to complete their life cycle in the cool Northwest growing season; in most cases, these blueberries are not suitable for the colder conditions of eastern Washington. Crosses between northern highbush and lowbush blueberries, often called half-high blueberries, have been developed to withstand colder temperatures, and they are the most likely to do well in USDA zones 6 and 7 in eastern Washington.