Michigan State University Extension
Home Horticulture - 01701524
The lowbush blueberry is the low growing type that grows wild. The highbush blueberry is the type usually planted in commercial plantings. This information applies to the highbush blueberry. Grow varieties that mature at different times to prolong the harvest. Blueberries do not need cross pollination in order to produce a crop. Some varieties are: Bluecrop, Bluejay, Rubel and Jersey.
Highbush blueberry needs an average growing season of 160 days and is badly injured by temperatures of -20 to -25.
A loose soil is best. A mixture of sand and peat gives excellent results. Heavier textured soils are suitable if acidic and high in organic matter. Peat soils may stimulate late growth that fails to harden before winter or such soils are often in frost pockets. Blueberries must have an acid soil with a pH between 4 and 5.1. The pH can be lowered with applications of sulfur. If the pH is very high it may not be practical to try to lower the pH. A soil with a constant moisture supply is best. The water table should be within 14 to 22 inches of the soil surface most of the time but good surface drainage is needed.
Good air drainage reduces frost injury and helps control diseases. Problem weeds should be controlled before the blueberries are planted. Unless a home gardener has almost ideal conditions for blueberries it may be wise to grow some other fruit.
The best planting stock is 2 or 3 years old. The 3 year old stock usually costs more. Avoid stock older than 3 years. The best planting time is early spring. Set the plants 4 feet apart in rows 10 feet apart. The plants should be set about 2 inches deeper than they were growing in the nursery. Mix a shovelful of acid peat into each hole at planting time if the soil is sandy and low in organic matter.
Blueberries are shallow rooted so cultivation should be no deeper than 2 to 3 inches. A cover crop may be sown after harvest.
Most organic materials may be used but they should be allowed to weather before being applied to the blueberries. The mulch should be about 6 to 8 inches deep. Double the amount of nitrogen applied until the mulch has decomposed. Leguminous mulches such as clover or soybean vines may be harmful.
Avoid using nitrate forms of nitrogen and chloride forms of potassium. The nitrate and chloride may be toxic to blueberries. Use a blueberry fertilizer such as 16-8-8-4. The 4 refers to magnesium. If blueberry fertilizer is not available use ammonium sulfate or urea.
Fertilize new plants about 4 weeks after planting. Sprinkle the fertilizer thinly about 12 to 18 inches from the plant crown.
Established blueberries are fertilized in April before growth starts. Spread the fertilizer evenly and keep it off wet plants to prevent injury. A very sandy soil may need a second fertilization. If so, use 50 to 100 pounds of ammonium sulfate after spring rains. The following chart tells how much fertilizer to use per plant.
Year in Field Ounces per Plant 1 or 2 1 3 1.5 4 2 5 3 6 4 7 4.5 8 or more 5
A foliar analysis may be helpful in identifying specific nutritional needs.
Fruit is produced on the previous seasons wood. New plantings need no pruning until about the 3rd year. Then prune during the dormant season to remove the small twiggy growth near the base of the plant. After the 3rd year, remove dead or injured branches, fruiting branches close to the ground, spindly bushy twigs on mature branches, and older stems of low vigor. Heavier pruning gives larger berries but fewer of them. Remove old black canes at the ground level.
Blueberries need 1 to 2 inches of water at 10 day intervals during dry weather.
Blueberries ripen over a period of several weeks. Three to 5 pickings are needed to harvest all the berries. Pick only the ripe berries. A reddish tinge means the berry is not yet ripe.