Pruning of blueberries is undertaken in both the establishment and the production stages. Pruning during establishment assists in vigorous growth optimum plant shape. Pruning for increased production is necessary after establishment, as blueberries respond with higher berry production to the removal of old, thin and twiggy growth. A controlled plant shape will result in good producing cane growth and strength, and hence optimum berry production.
Regular pruning of southern highbush blueberry plants should begin in the fourth or fifth year after planting depending on the vigor of the plants. Plants generally also respond to a light initial pruning at planting to stimulate new vegetative growth. Some pruning also takes place on small plants in the early years to remove flowers and fruit to encourage vegetative growth.
Annual pruning should stimulate new growth and keep the plant yielding large crops of big berries. Prune also to remove unproductive, old, diseased, dead, or dying wood. Prune to remove branches that are too low or not upright. Prune to thin out overcrowded canes in the center of the plant. Remove any thin or twiggy wood near the top as time allows and any thin growth from the base of the plant. This will not produce fruit. Upright varieties require less shaping pruning while bushy, and spreading types require pruning training to develop upright growth.
In mild climates, with long growing seasons, the heaviest pruning should come in the summer following harvest. This enables a long period for new vegetative growth before the bud development on the canes changes from vegetative to flower buds in the fall. Fruit forms on lateral branches that develop several months prior to harvest in the evergreen system or during the previous year where dormancy and leaf fall occur. The amount of fruit production depends on these being strong canes. Strong canes that grow in late summer produce fruit buds at their tips. If desired, these canes can be thinned or cut back in winter also but this is at the expense of their fruiting tips.
It is important to determine if new cane production has been sufficient to maintain or increase yield. Prune all wood that has born fruit the previous year and take these branches back to the next lower strong, young growth. Prune any horizontal, low growing branches or occasionally these canes will develop more upright branches if cut back. Assess the plant and continue with fine pruning and tipping branches that have died back.
Some varieties are more open with some branches that lay out. These branches should be tipped or cut back to upward growing branches. Tipping will cause new secondary upward oriented branches. Other varieties are more upright and while their overall shape is good they may require more thinning to open the center of the plant. Some growers will also use single wire trellises on each side of the row for more spreading plant types to aid development of the upright plant shape.
Prune young bushes at planting time to stimulate new vegetative growth. One-fourth to one-third of the bush may be removed. With more mature bushes, remove up to 1/6 of the foliage area. The flowers and fruit should also be stripped from young, small plants for at least the first 1-2 seasons depending upon the size of the plants.
Winter or early spring pruning is primarily directed at thinning the fruit load. Flowers and fruit may be pruned or stripped from part of a branch to reduce the fruit number and increase the fruit size. The amount of thinning will depend upon the variety and fruit load relative to the vegetative area of the plant. Larger plants and more vigorous branches can support heavier fruit load.
Beginning in year 5 or 6 depending on plant vigor, the oldest cane should be cut back to the base at or near ground level. Allow a new cane to replace this cane and thus renew the entire plant every 5 years if there are an average of five primary canes per plant.
