An example of a well-pruned blueberry plant following its late winter pruning.

Photo courtesy Doug Van Allen

Barbara Faurot

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March is a great time to prepare blueberry plants for a successful season.

Blueberries are members of the genus Vaccinium, related to the rhododendron and azalea. With more than 35 species native to North America, wild or “lowbush” blueberries have been an important source of food for Native American communities for thousands of years.

In the early 1900s, Elizabeth White, daughter of a cranberry farmer in the pine barrens of New Jersey, read a ground-breaking book by field botanist Dr. Frederick Coville, “Experiments in Blueberry Culture.” White partnered with Coville, later chief botanist for the USDA, to lay the groundwork for our modern “highbush” blueberry varieties. 

I turned to a local expert, Doug Van Allen, to share some tips on blueberry needs and care. Doug is a WSU Extension Master Gardener in Jefferson County who has been growing blueberries and other small fruits for more than 25 years. With 300-plus hours of annual volunteer service as a Master Gardener, Doug also took some time to share some blueberry wisdom with readers of “Garden Notes.”  

Before getting into the management tasks, a review of blueberry needs may be helpful: 

​1. Blueberries grow best in fertile, well-drained soil with a pH of 4-5.5. Elemental sulfur can be used to lower pH. 

​2. Being shallow rooted, they don’t like competition for water or nutrients. Keep all grass, weeds, and other plants away, at least a couple of feet beyond the drip line.

​3. For Northern Highbush varieties, the most common type in Western Washington, spacing should be 5-7 feet (7 feet is better).

​4. To thrive, blueberries should get the equivalent of an inch/week of water during the growing season. Ideally, use hand watering, soaker hoses or drip tape. That said, I watered my patch with an oscillating sprinkler for several years with no adverse effects.

​5. Annual pruning, fertilizing and mulching is highly recommended.

​6. Full sun is ideal.

Pruning. For younger and smaller plants, very little pruning may be necessary beyond cutting out dead, crossing and diseased branches along with any “twiggy” growth. As spring approaches, keep pruning for larger plants on the lighter side. 

General pruning, best done in February, includes cutting out branches that grow towards the center of the plant and possibly heading back the plant if it’s getting too tall. Consider thinning some of the older canes that are in the ¾- to 1-inch diameter size. Berries grow on the tips of last year’s wood (laterals) that are coming off of two year or older canes. Production declines up to about eight years, at which point it may not be worth it to keep the canes. A mature clump of canes should be a mix of 6-12 newer and older canes. When canes are cut, they should be cut at ground level. When branches are thinned, make the cut at a “junction” with another branch or cane. A good pruning guideline is to not remove more than 30 percent of a bush (not including dead wood).

The good news is that blueberries are pretty forgiving regarding pruning.

Fertilizing and mulching. To keep it simple, use an organic rhody and azalea food, typically around a 4-5-3 NPK. On smaller plants, spread a generous cup of fertilizer around the plant out to the drip line and gently scratch it in, and repeat two more times on a monthly basis starting in March. Larger established bushes could use two to three cups for two to three months. It’s important to spread fertilizer evenly around the plant, as one side doesn’t feed the other. The ideal growth of branches during a season should be in the 6-12 inch range.

Mulching is super important with the possibility of using a number of different materials. Many commercial growers use sawdust because it’s cheap and consistent. Other materials could be wood chips, hog fuel, leaves, and my favorite, shredded fir and hemlock bark. If using sawdust, be sure to add a little extra fertilizer to counteract sawdust’s hunger for nitrogen. 

Curiously, compost is not recommended because most compost has a pH of 6.5 to 7.5, too high for blueberries. A system I use for laying down mulch is to do the March feeding of fertilizer (scratched in) first, then mulch around the plants 2 to 3 inches thick. Subsequent feedings are scratched into the mulch and then watered in.

With these steps, you’re on your way to a productive blueberry patch. Observing what happens with the plants is the best way to customize and adjust their care. DON’T FORGET TO WATER.

Here’s to much success in your garden!

A great free publication, published by WSU Extension, “ Growing Small Fruits in the Home Garden,” covers blueberries as well as other small fruits. 

Here’s the link: http://pubs.cahnrs.wsu.edu/wp-content/uploads/sites/2/2016/04/em103e.pdf

For any questions about home gardening, Master Gardeners at the Online Plant Clinic are always available to help: https://extension.wsu.edu/jefferson/gardening-2/plant-clinic/. Beginning in mid-April, the Plant Clinic will host live Zoom sessions. 

(Barbara Faurot is a Jefferson County Master Gardener and Master Pruner, and works with volunteers who serve as educators in gardening and environmental stewardship.)