How to Grow Blueberries in the Pacific Northwest

Although the Pacific Northwest is popularly defined by the rainy climate of western Oregon and Washington, the term correctly refers to both states plus parts of Northern California and western Idaho. The climates of Oregon and Washington are divided by the Cascade Mountains. Western parts of both states -- as well as Northern California -- generally have mild winters and cool summers, while eastern parts of the two states -- and sections of western Idaho -- have cold winters and hot summers. Choosing the right blueberry variety for the climate and selecting the proper garden site are keys to an abundant berry crop.

Northern highbush cultivars (Vaccinium corymbosum) are the preferred variety for cultivating in the Pacific Northwest. They will grow in U.S. Department of Agriculture plant hardiness zones 4 through 7. Lowbush cultivars (Vaccinium augustifolium, USDA zones 3 through 6), which grow 8 to 18 inches high, will also grow in the Pacific Northwest, though they have smaller yields than highbush cultivars.

Southern highbush varieties (Vaccinium corymbosum x darrowi, USDA zones 7 through 10) have low yields in the region. Rabbiteye cultivars (Vaccinium ashei, USDA zones 7 through 9) developed in climates with long, hot summers; if they're grown in the shorter, cooler summers of the Pacific Northwest, they tend to yield smaller berries that often do not have enough time to fully ripen.

Northern highbush blueberries grow 5 to 9 feet tall and do not need pollen from another plant to yield blueberries, but if they are planted with another highbush cultivar they will grow more berries and the berries will be larger.

Oregon State University horticulturalists recommend these highbush cultivars, listed in order of ripening.

‘Duke’ (Vaccinium corymbosum ‘Duke’), USDA zones 4 to 7

‘Earliblue’ (Vaccinium corymbosum ‘Earliblue’), USDA zones 5 to 7

‘Spartan’ (Vaccinium corymbosum ‘Spartan’), USDA zones 5 to 7

‘Bluecrop’ (Vaccinium corymbosum ‘Bluecrop’), USDA zones 4 to 7

‘Jersey’ (Vaccinium corymbosum ‘Jersey’), USDA zones 4 to 7

‘Blueray’ (Vaccinium corymbosum ‘Blueray’), USDA zones 3 to 7

‘Chandler’ (Vaccinium corymbosum ‘Chandler’), USDA zones 4 to 7

‘Elliot’ (Vaccinium corymbosum ‘Elliot’), USDA zones 4 to 7

The Pacific Northwest Extension service, a consortium of Oregon State University, Washington State University and University of Idaho extension services, offers a list of more than 30 highbush blueberry cultivars for climates found in the Pacific Northwest.

Pacific Northwest nurseries typically sell 2-year-old plants for late April planting. Plant them in the open 4 to 5 feet apart in rows 8 to 10 feet apart. Blueberries like full sun. The shade of nearby trees will reduce berry yield, provide refuge for birds that eat the berries and block air circulation.

The soil should drain well. If it doesn’t, bank the soil for a raised bed. Blueberry leaves will turn yellow and the plant will die if the soil is outside the optimal, acidic pH range of 4.5 to 5.5. Pacific Northwest soil tends to be more acidic west of the Cascade Mountains and more likely to fall in the acceptable blueberry pH range than soil east of the mountains. Test your soil pH before planting blueberries; you can buy a test kit in most garden supply centers.

To lower soil pH, combine granular sulfur into the top 6 to 8 inches of soil at least three months before planting. Add 1/10 pound of sulfur to lower each pH number by 1/2 point for each 10 square feet of soil. For example, lowering 7.5 pH soil to 5 pH would require 1/2 pound of sulfur for a 10-square-foot site.

Blueberry plants need the most water in the spring when the fruit is developing and ripening, but they also need water in July to early August when buds are setting for the next year’s crop. A blueberry plant needs from 1 1/2 to 3 inches of water a week -- from 9 to 18 gallons -- either through frequent irrigation to keep the soil moist or through rainfall.

After planting, sprinkle 1 ounce of ammonium sulfate, 21-0-0, within 12 to 18 inches of each plant and water well. Repeat this application in the first week of June and the last week of July.

Sprinkle 1/4 ounce of nitrogen around each plant in April, May and June of the second year and water well. Apply 4/5 ounce of nitrogen in April, May and June of the third year. Increase the nitrogen in these monthly applications to 1 ounce the fourth year. From the fifth year on, apply 2 1/2 ounces of nitrogen in those months. Use ammonium sulfate (21-0-0) or urea (46-0-0) for the nitrogen.