Wednesday, February 20, 2013
How to grow Blueberries in S. Oregon
Blueberries can be tricky to grow in Southern Oregon. They like to grow in full sun, but their roots demand cool, loose, rich, moist soil, which doesn’t naturally occur here. So you have to make it.
They don’t like being planted in soil; they like to be planted in 6” of compost on top of the soil. Young blueberries have a spongy root system only about 4-6” deep. As they mature, they put down a deep root, but for several years the whole root mass is easily transplanted. As the compost is worked into the soil by worms, the soil is worked upward into the root mass. If you plant other “gallon” (#1) potted plants into plain compost, they will eventually be left high and dry as the compost evaporates; blueberries spread their roots through the compost and sink into the soil.
That compost will dry out fast if it is left uncovered, so cover it well with loose, coarse mulch which will shade and protect it. Pine needles, walk-on fir, or ¾” nugget bark work well; avoid fine bark, which kills soil. Blueberries need live, loose soil to thrive.
But those roots will be coolest and happiest if they are covered with a green ground cover with roots that grow through the blueberry roots to the soil beneath or grow on top of them. Lysimachia, also known as Creeping Jenny or moneywort, and small sedums grow on top; violets and strawberries grow through. Sedum is slow growing but easier to control, and is easily peeled off the soil and transplanted in large mats if you can find them.
Some ground covers grow in the same root zone and compete rather than cooperate with your blueberries. Blue star creeper killed a huckleberry in one of my yards. Sweet Woodruff has similar spongy roots and directly competes for space.
Water is critical to blueberry growth and survival. They can take a little dry, but too much too often will make them unhappy and eventually kill them, one reason why they like their roots covered with mulch and ground cover. They can take a lot of water in winter; the biggest, oldest bushes I’ve ever seen were growing next to a pond that flooded them most of the winter. If practical, site them in the wettest spot in your yard that gets sufficient sun but is not flooded in summer.
Southern Oregon is very hot in the summer. Northern blueberries might prefer a little afternoon shade. Southern rabbiteye blueberries, available in catalogs and some at Bi-Mart, can take our heat better. Northern turn brilliant red in the fall and lose their leaves; southern turn various colors in pink, yellow, and red and keep many leaves through the winter. Both types cross-pollinate; all bloom around the same time, regardless of when they ripen. Southern tend to bloom and ripen later, over a longer season.