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What to Know Before You Grow: Blueberries

Blueberries don't like most of the soils in Central Illinois. It's some of the best soil in the world, but for blueberries we have to make amendments that you can easily manage in your backyard. Our soil may be alkaline, but don't call us basic.

Blueberries require acidic soil. They prefer a pH of 4.8 to 5.2, which is below our average soil pH of 5.5 to 7.0 in most places in Central Illinois. If the soil is not acidic enough, the blueberry plants will not be able to take up the required nutrients from the soil, leading to stunted growth and yellow leaves.

A soil test can determine the pH where you would like to plant, and the testing company will even provide recommendations on how to amend the soil. They may suggest elemental sulfur, which is best applied in the fall. Ammonium sulfate can be used while the plants are growing to lower the soil pH.

The rates for ammonium sulfate are one ounce per plant at time of planting, three ounces for two year old plants, eight ounces for four year old plantings and 12 ounces for eight years or older.

But amending soils may not be enough. Some Illinois soils are too heavy, and amending he soil to improve drainage may be needed. The addition of organic matter or acidic peat moss will improve the growing condition of the soil. Raised beds or large pots could also be an alternative to the drainage issue and keeping the soil acidic.

Climactic challenges also must be managed. Blueberry plants are shallow rooted. The roots do not mine the soil seeking out water and they may not produce adequate berries if they are lacking moisture. They are especially susceptible to drought. We usually recommend an inch per week but this estimate may increase to two to three inches if temperatures are high. Although blueberries require at least five hours of full sun, some afternoon shade may be beneficial. Mulch is also a great strategy in conserving moisture for blueberry plants.

Choose healthy plants for spring planting that are known to do well in Illinois. Highbush cultivars, 'Blueray' and 'Jersey,' as well as hybrids (cross between high bush and low bush) 'Northland' or 'Patriot' are recommended for Illinois. High bush cultivars grows taller are a better adapted to our area than low bush types. The recommended spacing is four to six feet apart.

The canes that produce blueberries will be four to six years old, but blueberry plants still need to be pruned during the dormant season in early spring. Prune diseased or broken branches laying on the ground, or branches six years or older. Open the center of the bush, but leave strongest canes behind. Blossom removal is recommended for the first two years after planting for a strong establishment. The amount of blueberries harvested will grow as the plant gets older.