Blueberries

The term blueberry is applied to many species of Vaccinium which are mainly found throughout the northern temperate zone. The North American blueberries have received the most attention due to size, quantity and taste, and breeding programs have produced the superior selections of the northern highbush (V. corymbosum ). However, northern highbush cultivars have exacting cultural requirements. An appreciation for the conditions required can be gained by noting that a close relative, V.occidentale, thrives in the coastal redwoods. A prime requirement of the northern highbush is the need for a very acid soil (pH ~ 4.5). This species also disdains hot, dry temperatures. Recently work with the southern highbush blueberry (V. virgatum) and rabbit eye (V. ashei) has produced cultivars that are more tolerant of hot, dry conditions and higher pH. Blueberries in Southern California ripen from late May to August. More northern areas supply fruit from late June to autumn, and suppliers in the southern hemisphere produce fruit that is available during winter and spring.

Botany

The family Ericaceae (Heath) consists mainly of shrubs whose genera include Rhododendrons, Erica (heaths), Calluna (heathers) and Gaultheria (wintergreen). The genus Vaccinium contains about 100 species most of which have edible fruits. Of these the blueberry, bilberry (V. myrtillus), cranberry (V. macrocarpon), lingonberry (V. oxycoccus) and huckleberry (V. ovatum and V. vaccillans) are most prized for their fruits.

The huckleberry, is often confused with the blueberry; however, the fruit is easily discerned since it has only three seeds. Although the fruit flavor is almost indistinguishable from blueberries, little has been done to develop superior cultivars, particularly ones that are adapted to southern California.

Pollination Requirements

At least two varieties of the same species are needed.

Climatic requirements

Blueberries have a chilling requirement; however, the figures quoted usually have been determined under eastern US conditions and should be taken only as a qualitative guide to performance in southern California. Rabbiteye blueberries require the least winter chill (perhaps 100 to 200 degree hours below 45^oF) while some southern highbush cultivars may require more chilling. Northern highbush can require over 600 hours. However, 'Elliot', a northern highbush, which is said to require more than 800 hours does well and produces in Pasadena where the chilling is less than 300 hours. Winter shade could account for some of this disparate performance. All blueberries like moist conditions and in hot, dry areas shade cloth may be necessary.

Soil Requirements

Blueberries demand conditions that are not normally found in southern California. In the wild, blueberries are an understory plant preferring the areas where there is a break in the overhead canopy. Decaying leaves produce a highly acidic soil (4 to 4.5 pH) and conditions are usually moist. Blueberries are often found in swampy areas. In cultivation pH must be corrected to at least 5. This can be done by adding peat moss and/or leaf mold to the soil before planting. Incorporation of sulfur or aluminum sulfate is also recommended. Attention must then be paid to maintaining a low pH (see fertilization).

Cultural Requirements

Spacing and training

Plants are usually spaced 3 to 6 feet apart with 10 feet between the rows. No supports are needed, but some provision for shade in inland areas might be necessary.

Watering

Blueberries like humid conditions. Misting in hot dry conditions will be helpful. The plants should not be allowed to dry out.

Fertilization

If the pH is too high the plants will show chlorosis. Acidic corrections will probably have to be made on a regular basis since rain will leach out additives and alkaline irrigation water will raise soil pH. Use of acidic mulches and fertilizers is the usual approach. Acids such as phosphoric and sulfuric have been used, but care must be taken in their handling. The plants are susceptible to fertilizer burn particularly during the first year.

Pruning

Plants are pruned to let light in and to maintain desired picking height. Some southern varieties such as 'Woodard' are much more vigorous and require aggressive pruning while most of the newer southern hybrids will require far less pruning.

Pests and Diseases

Blueberries are not prone to disease and pest problems.

Propagation

Propagation is normally done by rooting of softwood cuttings. Hardwood cuttings are more difficult.

Harvesting and Storage

Blueberries are considered to be very perishable. However, if handled carefully, they keep better than raspberries or strawberries.

Fiscal

Undetermined

Market

The prime market for local blueberries is the fresh local market, especially the early spring market when more northern grown berries are not available. A possibility exists for extra early berries since some of the southern varieties have a tendency to bloom as early as January or February.

Compiled by Robert Vieth, Master Gardener