Acidic soil gives new blueberries a boost

Plant blueberries in the spring. (Photo by Lynn Ketchum)
Blueberries produce ripe fruit from late June through September. (Photo by Lynn Ketchum)
Last Updated: 
April 11, 2014

CORVALLIS, Ore. – Plant blueberries now for a great crop of sweet, healthful fruit in the future.

Three categories of blueberry plants are best-suited for Oregon climates: Northern highbush varieties, rabbiteye varieties and half-high varieties, according to Bernadine Strik, a berry specialist with the Oregon State University Extension Service.

Cold-hardy Northern highbush blueberries are some of the most commonly planted in the United States, Strik said. These 4- to 6-foot tall plants grow well in any region in Oregon, she said. Of these, Strik recommends Spartan, Reka, Bluecrop, Jersey and Chandler. For the Willamette Valley, she also recommends a relatively new variety, Legacy.

If you want to try rabbiteye blueberries, Strik recommends Powderblue and Ochlockonee as the best ones for flavor. Rabbiteye blueberry plants, which are too cold-sensitive to grow outside the Willamette Valley, need lots of space as they get over eight feet tall, she said. Their fruit ripens in late summer.

Half-high blueberries are an option for limited space as they only grow 1½- to 3-feet tall, she said. They are suited for cold regions and containers, Strik said. She recommends Polaris, Northsky and Northcountry varieties.

Keep in mind that you must grow two rabbiteye blueberry varieties that need to pollinate each other to get fruit, Strik said. It’s also a good idea to grow more than one highbush or half-high type for good cross-pollination. Any two varieties will do, she said.

For more cultivar recommendations, see the newly revised OSU Extension publication Blueberry Cultivars for the Pacific Northwest.

Remember that blueberry plants prefer soils with a high organic matter and good drainage. They are adapted to acidic soils with a pH of 4.5 to 5.5, Strik said.

"If the pH is not in a suitable range, then the plants cannot take up the nutrients they need to grow," she said.

Always test your soil to determine its pH before planting, Strik said. Send the soil sample to one of the labs listed in OSU Extension's publication, Laboratories Serving Oregon. Learn how to take a soil sample in OSU Extension's publication, A Guide to Collecting Soil Samples

If the soil test reveals that the pH is above 5.7, then you will need to acidify, or lower the soil pH, Strik said. Do this by incorporating elemental sulfur into the soil, she advised. Sulfur is available in a powder or pellet form at farm supply stores. It’s important to use the right amount of sulfur so the pH doesn’t drop too low for ideal blueberry plant growth, Strik said. To figure out the right rate of sulfur, see the OSU Extension publication Growing Blueberries in Your Home Garden.

It takes at least six months for the sulfur to react with water in the soil and create acidification. If your soil pH is not in the right range for planting this spring, follow instructions for lowering soil pH and delay planting blueberries until early October, Strik advised.

It’s a good idea to add organic matter to the soil prior to planting as well, she said. Strik cautioned gardeners not to incorporate composted yard debris or manure into the soil, as these materials have a high pH — typically 7 to 8, she said. Instead, she recommends incorporating bark or sawdust to improve plant and root growth.

Strik further advised pruning off the flower buds or flowers at planting so that the plant does not produce any fruit in the planting year. Fruit buds are the "fat" buds at the tips of the shoots of the plant.

"Research I've done shows that letting young plants produce fruit in the planting year, or the year after an October planting, reduces root and plant growth," said Strik, a professor in OSU's College of Agricultural Sciences. "Plants need to use all their energy to build the plant instead of to produce fruit in the first year."

The 22-minute video A Grower's Guide to Pruning Highbush Blueberries offers more detailed pruning advice. It is available in Spanish

Author: Denise Ruttan
Source: Bernadine Strik