Fresh blueberries are one of summer's best-tasting treats. They are excellent in pies, muffins, and pancakes. Blueberries are also a great topping for breakfast cereals.
Blueberry plants can be successfully grown in Iowa. However, they do have special growing requirements.
The blueberry is a member of the Heath or Ericaceae Family. Blueberry plants require a sunny location and well-drained soils high in organic matter. Avoid wet, poorly drained soils. Blueberries are susceptible to root rots in poorly drained soils. Soil pH is also extremely important. Blueberries require an acid soil of pH 4.0 to 5.5. Since the pH of most Iowa soils is above this range, the soil pH must be lowered to successfully grow blueberries. Home gardeners can lower their soil pH by adding Canadian sphagnum peat to the soil. Sulfur can also be used to acidify the soil. Since sulfur reacts slowly with the soil, it should be applied and incorporated a year before planting. The following table lists the approximate amount of elemental sulfur required in pounds per 100 square feet to lower the soil pH to 4.5.
Aluminum sulfate should not be used to acidify the soil as large amounts of this compound can be toxic to blueberry plants.
Two types of blueberries (highbush and half-high blueberries) can be successfully grown in Iowa.
Highbush blueberries are hardy in central and southern Iowa. Plants develop into 6 to 8 foot shrubs. Suggested varieties for Iowa include Blueray,' Bluecrop,' Patriot,' Jersey,' and Elliott.'
Half-high blueberries possess greater cold hardiness and are the best choice for gardeners in northern Iowa. Plants are relatively small (varieties commonly grow only 2 to 3 feet tall) and produce small to medium size berries. Suggested varieties are Northblue,' Northcountry,' Northsky,' and St. Cloud.'
Spring is the best time to plant blueberries. The roots of dormant, bare-root plants should be soaked in water for about an hour before planting. Prune back the plant by 1/2 by removing the small side branches and by heading back the main branches. When using Canadian sphagnum peat to acidify the soil, dig a hole approximately 12 to 18 inches deep and 2 to 3 feet wide. Set the plant at the same depth it grew in the nursery. Then backfill with a 50:50 mixture of soil and moist peat. After planting, thoroughly water each blueberry plant. Highbush blueberries should be spaced 4 to 6 feet apart. A 3 to 4 foot spacing is adequate for the smaller half-high blueberries. Plant 2 or 3 blueberry varieties to insure adequate pollination and fruit set.
Blueberries have a shallow, fibrous root system. Plants quickly become stressed during hot, dry weather. To help retain moisture and control weeds, apply 2 to 4 inches of mulch around blueberry plants. Sawdust, wood chips, pine needles, and shredded leaves are excellent mulching materials. During dry weather, water plants weekly.
Blueberry plants should not be allowed to bear fruit the first 2 years after planting. Any blossoms which form should be removed. Removal of the flowers will maximize vegetative growth and increase yields in later years. Blueberry plants should come into full production by the fifth or sixth year. Gardeners can expect to harvest 5 to 10 pounds of fruit per plant from mature highbush blueberries. Half-high blueberries generally produce 1 to 3 pounds per plant.
Once established, an annual application of an acid-producing fertilizer, such as ammonium sulfate, in early spring is sufficient for blueberries. Apply 1/2 to 1 pound of ammonium sulfate per 100 square feet of garden area. Ammonium sulfate supplies nitrogen to the plants and also helps to maintain soil acidity.
In Iowa, blueberries generally have few insect and disease problems. Birds are the biggest threat to the crop. If left unchecked, hungry birds may devour much of the crop. While scare devices may be helpful, netting is the most effective way to protect the crop. Netting should be placed over the plants when the fruit begin to turn color. Hang the netting over some type of support structure with the edges of the netting buried or anchored to the ground to prevent bird entry from below.
Blueberries don't have to be relegated to the backyard garden. Blueberries are also attractive ornamental shrubs. Plants produce white to pink, urn-shaped flowers in the spring. They also produce excellent fall leaf color. The fall foliage consists of shades of yellow, orange, and red.
This article originally appeared in the March 23, 2001 issue, pp. 26-27.
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