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written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

I can’t believe it – commercial blueberries growing in the Columbia Basin! A member of the heath (Ericaceae) family, blueberries are related to rhododendrons and azaleas. Members of this family grow best where temperatures don’t get extremely hot. Their fibrous roots are shallow and prefer well-drained acidic soils that are high in organic matter. The roots are sensitive to injury from extremely hot and cold temperatures. They also don’t thrive when irrigation water is alkaline or is high in salt.

These special growing conditions haven’t stopped local commercial growers from taking extraordinary means to produce blueberries in our region. Should local gardeners try? While the obstacles are not insurmountable, growing blueberries here takes special effort.

The first obstacle is soil pH. Many of our garden soils have a pH of 7.5 to 8. Blueberries do best with a pH of 4.5 to 5.5. To lower the pH and make the soil more acidic, add three pounds of sulfur per 100 square feet of soil and mix in by tilling to 8 inches. For best results, the addition of sulfur should be done about a year before planting.

The next impediment is the soil’s organic matter content. Most area soils usually contain less than 1 percent organic matter. Blueberries prefer soils that have at least a 3 percent organic matter content. This requirement can be met by applying a 6-inch layer of well-rotted compost to the bed and tilling to 8 inches.

Amending the soil is best done by planting blueberries in beds. This makes it easier to modify soil in a contained area. The original addition of sulfur to the soil won’t “fix” soil with a high pH problem. Young plants will need to be fertilized with an acidifying fertilizer three times during the growing season – spring, early summer and late fall. Ammonium sulfate (21-0-0) is one of the best choices. Apply three to four tablespoons per plant per fertilization for the first three years, starting the year after planting. Later in the plant’s life, the amount of fertilizer applied in spring and early summer will be increased. The sulfur needs to be gently scratched into the soil.

Note: Do not use aluminum sulfate to acidify the soil. It can cause problems with aluminum toxicity.

Yet another hindrance is our climate, especially the hot summer temperatures and low humidity. Place plants where they will get full sun, but are sheltered from wind or excessive heat. Avoid planting them on the south or southwest sides of buildings. A 2-inch organic mulch will protect roots from cold and heat extremes.

Blueberries also are sensitive to drought. Irrigation should be applied often enough to keep the entire root zone moderately moist. Wet soils can lead to root rot. The layer of mulch will help. The plants are subject to winter drought and should be watered in fall and during the winter if the weather is mild and dry.

Growing blueberries in this region is a challenge for gardeners, but it can be done if you’re willing to provide for their special needs. Here are some other tips:

•Plant in early spring and prune hard to stimulate new growth. Don’t let plants set fruit the first year, and allow light crops for the next two years. Don’t fertilize during the first growing season.

•While blueberries will produce fruit without cross-pollination, planting two varieties can enhance fruit production.

•Renew mulch every year. It helps conserve moisture.

Published: 4/21/2007 4:10 PM



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