YOUR GARDEN: Kym Pokorny

Good soil key to garden blueberries

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Kym Pokorny

When it comes to fruit in the garden, blueberries rule.

Favored for their sweet flavor, blueberries are also known for their high level of antioxidants, thought to help protect the body against free radicals and chronic diseases associated with aging.

Highbush blueberries, the most common in Oregon, are perennial, long-living deciduous shrubs with a mature height of 5 to 7 feet, according to Bernadine Strik, a berry specialist for Oregon State University’s Extension Service. Attractive as ornamentals, they produce a profusion of white or pink blossoms in spring and colorful foliage in fall.

“You can grow plants in beds, rows, hedges or individually,” Strik said. “Dwarf and semi-dwarf cultivars can be grown in containers.”

Fruiting season in Oregon is from late June until September, depending on the variety.

It’s best to plant more than one variety of blueberry, Strik advised.

“Although most northern highbush cultivars are self-fertile, cross-pollination produces larger berries,” she said. “And, if you plant two or more cultivars that ripen at different times, you’ll lengthen the harvest season.”

Northern highbush varieties grown in gardens in Oregon include, in order of ripening: Duke, Earliblue, Spartan, Patriot, Bluecrop, Jersey, Blueray, Legacy, Chandler and Elliott. The Extension guide “Blueberry Cultivars for the Pacific Northwest” offers descriptions of these and other blueberries.

The plants, which can live up to 50 years, need lots of sunshine and specific soil requirements. When choosing a site, Strik recommended avoiding areas surrounded by trees, which can provide too much shade, compete for water and nutrients, encourage hungry birds and deter air movement around the new plants. The berries grow best in well-drained, light, sandy loam that is high in organic matter and with a pH between 4.5 and 5.5.

Test the soil pH a year before planting. If you need to make the soil more acidic, it can take more than six months. According to Strik, poor plant growth from soil pH that is too high is the most common problem when growing blueberries in a home garden.

If the pH is between 5.7 and 6.5, Strik said lower it by adding finely ground elemental sulfur before planting. The amendment is available at garden centers.

The amount needed depends on how much the pH needs to be lowered and the soil type. More detailed instructions on changing pH, weed control, mulching, fertilizing, pruning, watering and care of established blueberry plants are available online in the OSU Extension publication “Growing Blueberries In Your Home Garden.”

If you decide to grow several plants, it’s better to group them in a bed or row rather than scattering them around the garden, Strik said. You’ll get better results preparing an entire bed, rather than digging holes and preparing soil for individual plants.

Although blueberries require a uniform supply of water, they will not tolerate poor drainage. Raised beds can provide adequate drainage and aeration if they are from 12 to 18 inches high and 3 feet wide. They can be constructed with wood walls, or you can make hills with just soil and sawdust.

“Before planting, incorporate organic matter such as Douglas-fir sawdust or bark to improve soil aeration and drainage,” Strik said. “Yard debris compost often has a high pH — over 7.0, compared to 4.0 to 4.5 of Douglas-fir sawdust — and can be high in salts, so is not desirable for blueberries.”

Spread sawdust to a width of about 3 feet and a depth of 3½ inches. To aid in decomposition, add two pounds of nitrogen per 100 feet of row length (10 pounds ammonium sulfate, 21-0-0). Dig or till in the sawdust and fertilizer.

Plant healthy 2-year-old plants from a reputable nursery in October or from March through April.

“Prune off flower buds at planting, and do not allow plants to produce fruit the first season,” Strik said. “Be patient. Flower and fruit production hinders growth, and it’s important that plants grow well the first year.”

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