These include the lowbush blueberry (Vaccinium angustifolium), which is of commercial importance in Maine and Canada; the rabbiteye blueberry (V. ashei), which is grown commercially in the southern United States; and the highbush blueberry (V. corymbosum), which is the commercial blueberry of importance in Pennsylvania and in the Mid-Atlantic and Midwestern regions of the United States. The information that follows pertains solely to highbush blueberry production since this type of blueberry is of primary interest. Managing lowbush types in a home garden tends to be a challenge because the plants spread and form a dense mat. Rabbiteye blueberries can be grown in the extreme southeastern part of the state; their culture is similar to that described below for highbush production. Little information is available on performance of various rabbiteye varieties, however. Production of rabbiteye plants in cooler areas of the state has been very variable.
The Blueberry Plant
Original breeding work and research was conducted by Mrs. Elizabeth White and Dr. Frederick Coville, beginning shortly after the turn of the century.
The blueberry plant is a perennial, consisting of a shallow root system and woody canes that originate from the crown of the plant. The root system is very fibrous but devoid of root hairs. (Root hairs in most plants function by increasing the surface area of the root for water and nutrient uptake.) This characteristic makes the blueberry plant very sensitive to changing soil water conditions.
A mature cultivated blueberry usually has 15 to 18 canes. Its growth habit varies among varieties, with some bushes growing very upright and others having a more spreading growth habit. The fruit is borne on buds that are formed the previous growing season.
A blueberry planting should be planned at least one year in advance. The soil should be tested and sulfur and phosphorus applied (if needed) during the fall prior to planting.
Because most blueberry varieties are not well adapted to heavy upland soils, most soils will require considerable amendment with organic matter if plants are to thrive. Compost application and/or the use of cover crops in the year prior to planting will increase soil organic matter. Sawdust or peat moss also should be worked into the planting hole, replacing about one-half of the original soil with the organic material. After watering in and applying the fertilizer, mulch the plants heavily along the length of the row with about 4 inches of rotted sawdust or other organic matter. Avoid using green sawdust since it may burn the tender green stems and will compete with the plant for nitrogen.
Immediately after planting, prune back 50 to 60 percent of the wood. Remove the flowers from two-year-old plants completely so the plant will become well established. Sacrificing this small amount of fruit is well worth the dividend of establishing a planting that will fruit for 50 years or more if well maintained! Some of the crop also should be removed the following year to encourage sound establishment.
If the soil is properly prepared, only nitrogen fertilizer is required. Do not fertilize in the first year since the root system is very susceptible to root burning at this stage.
In subsequent years, always fertilize with ammonium sulfate in March or April. To each plant, apply 4 ounces of ammonium sulfate in year two, 5 ounces in year three, 6 ounces in year four, 7 ounces in year five, and 8 ounces in year six and subsequent years. Retest the soil every 5 years or so to make sure that the soil pH is in the correct range. If nutrient deficiency symptoms (e.g., light-green or red leaves in the summer, poor growth, poor yield) appear, it is likely that the soil pH is no longer in the optimum range of 4.5 to 5.0.
Most plantings will produce satisfactory crops when only one variety is included, but pollen from other varieties generally will result in increased yields, larger fruits, and earlier ripening.
A planting design in which a row of one variety is alternated with a row of another variety will encourage cross-pollination. Make sure there is good bee activity. A honeybee hive in the vicinity will provide consistently high yields and better berries.