The cultivated blueberry, sometimes called the highbush blueberry, is closely related to the wild European bilberry or blaeberry found in many of our upland areas. While the wild bilberry is a small plant with varying amounts of tiny intensely flavoured berries, the highbush blueberry grows on tall plants and produces heavy crops of large blackcurrent-sized berries.
Genetically speaking the cultivated blueberry is little different from the wild highbush blueberry Vaccinium corymbosum of eastern North America, but some modern cultivars also have some Vaccinium angustifolium (N.American low bush blueberry) in their ancestry. V corymbosum/angustifolium hybrids produce smaller more compact bushes of 1.0-1.5 meters, while pure V. corymbosum cultivars can grow to 2.5 or 3 meters if not regularly pruned. All cultivars are relatively long lived, and in good conditions will live for up to half a century.
The native peoples of North America have used the blueberry for thousands of years. They did not cultivate the plant but managed the healths where it grew wild by burning the vegetation every few years to kill off invasive plants and encourage new growth. The European immigrants to the New World soon discovered blueberries and saw them as a valuable wild food. By the late eighteenth century settlers were staking claims on blueberry picking grounds and by the early to mid-nineteenth century blueberries were being collected on a commercial scale. They were used to feed troops during the American Civil War.
The requirement of blueberries for acid ground was not understood for a long time, and as a result, early attempts at cultivation were not successful. Elizabeth White, the daughter of a successful cranberry grower, and Frederick Coville, a botansit working for the US Department of Agriculture, are credited with the pioneering of blueberry cultivation in the early years of the twentieth century. Working both together and seperately, they collected good specimens from the wild and instigated a large scale propagation programme involving thousands of plants.. The outcome was a number of distinct cultivars. One of these, Rubel (1912) is still in cultivation today. Other early cultivars still common include Jersey (1928) Coville (1936) and Dixy (1936).
In 1941 the cultivar Bluecrop, a [Jersey x Pioneer] x [Stanley x June] cross, was introduced. Its drought tolerance and ability to produce big crops year after year soon gave it a dominant position in commercial blueberry plantations, which persists to this day. However, in recent years, smaller, more compact cultivars have become popular.
Cultivation
Blueberries require good drainage yet an adequate supply of water during the growing season, especially during fruit production. They do best in a dry acid soil of pH 4.5-5.0, though will tolerate higher pH if mulched with acidfying material such as peat, pine needles or pine bark. Peaty soils that are prone to waterlogging may be improved with the addition of copious amounts of sand, combined with deep drainage. Conversely, the water retention capability of excessively sandy soils may be enhanced by adding generous amounts of organic material derived from leaves, bark or pine needles.
When grown on a commercial scale, bushes are spaced at 1.0-1.5 meters, with rows 2.4-3.0 meters apart. Typical density is 2500 plants per hectare. Closer spacing will increase early yields, but at the cost of production in the long run. Yields on mature bushes are in excess of 2kg per annum.
Blueberries are also very suited to pot culture, which can solve the problem of unsuitable soils. Bushes grown in pots should be gradually potted up into larger pots over about a ten year period, with the ultimate pot size being 70-110 litres. For mature pot-grown plants, yields of 0.5-1kg per annum are typical.
One of the best features of blueberries is that good yields are possible even in exceptionally poor summers. They just love summer rain. Once picked they have a fairly good shelf life - certainly far longer than most other soft fruit.
When buying stock from a nursery, take care to avoid plants that are severely pot-bound, as these will develop very slowly. Gently teasing out the root-ball prior to planting will help the plant develop new roots. Plants in very small pots (1-2 litres) will take many years to become established.
Cropping
Early varieties will begin cropping late July and continue for the month of August. Mid season varieties will crop from early August until mid September while late varieties will continue producing fruit until late September or even early October.
Nutrition
Blueberries compare quite well to most other fruit in terms of nutrition. 100g of blueberries contain the following:
Carbohydrates 15 percent
Protein <1 percent
Water 84 percent
Fats <0.5 percent
Calories 57
100g of fresh blueberries also contain 10mg Vitamin C, 20 µg Vitamin K, small amounts of vitamins A, B and E, and most minerals, notably manganese.
Further reading
Blueberries, Cranberries and Other Vacciniums, by Jennifer Trehane of Trehane Nurseries, Dorset, England (Royal Horticultural Society 2004), is by far the best text on the subject.