Agriculture

Pruning Small Fruit Trees

By Lewis W. Jett, WVU Extension Service commercial horticulture specialist bberries

Pruning is one of the most important tasks needed to produce many fruits successfully. Pruning is performed to control size and shape of the plants as well as to achieve an optimal balance between leaf (vegetative) growth and fruit (reproductive) production.

Both small fruits and tree fruits require some degree of routine pruning during their growth. Small fruit plants that should be regularly pruned include blueberries, blackberries, raspberries, grapes and currants. Tree fruits, such as apples, peaches and cherries, should be pruned to maintain vigor and fruit size.

Proper tools required for pruning include hand-held pruners, loppers or saws. Pneumatic pruners are also available for pruning commercial-size plantings. All pruning tools should be sharp to provide a clean cut of plant material. Alcohol can be used as a disinfectant to clean pruning tools. Gloves may be needed if you handle vines and branches that may have thorns.

Prune blueberries annually approximately three years after planting. The first two years after planting, remove the flower buds are to encourage greater vegetative growth. Pruning is done to encourage new cane growth and prevent overproduction of fruit. Most fruit production is on the new canes.

When blueberries overproduce, their fruit size decreases. Pruning opens the canopy up to more light, thus increasing yields. Pruning methods vary according to blueberry variety. Some varieties produce a lot of canes near the center of the bush (‘Bluecrop’), and others have a more spread-out growth habit (‘Aurora’). Varieties that tend to grow tight canes within the center need to have the older canes removed from the center of the bush. Generally speaking, two or three of the oldest canes are removed each year. Detail pruning of the upper canopy removes branches that are growing too closely to each other. Also, any low-growing, diseased or dead branches should be pruned.

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Figure 1. Pruning of blueberry bushes increases overall marketable yield. Remove old canes and other dead or diseased canes from each plant.

Brambles such as raspberries and blackberries are pruned according to their growth habit. Brambles are generally biennial, meaning they have a year of vegetative growth followed by a year of fruit production. Many summer raspberries and blackberries follow this growth habit. After they are planted in the spring, no pruning is required the first year of establishment.

Summer red raspberries are pruned by removing the spent fruiting canes (floricanes) after harvest. In the dormant season, the canes are thinned to approximately four to six of the most vigorous canes per linear foot of row and lateral branches are shortened to 6 inches. The row should not be wider than 18 inches so any root suckers or shoots that emerge beyond this width should be pruned or dug up for transplanting in another area.

Black raspberries are a very popular fruit in West Virginia. Black raspberries produce ripe fruit in June or July in West Virginia. They should be pinched or tipped to keep the canes from arching to the ground. Tipping requires removing the top 1 inch of each cane to maintain a height of 3 to 4 feet. This practice also stimulates lateral branches, which results in a higher yield of fruit.

During the winter months, thin black raspberries to four or five canes per crown or hill, and prune the laterals to 10 to 12 inches on each cane. Blackberries are pruned by tipping during the growing season so that the plant height is no greater than 6 feet (Figure 2). Laterals and canes are shortened during the dormant season similar to black raspberries. Spent floricanes are removed and four to six canes per hill are kept for next year’s production.

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Figure 2. Blackberries are topped during the growing season to control canopy height and canes are removed and shortened in late winter.

Both hone gardeners and commercial producers should try growing the primocane blackberries and raspberries. These types of brambles produce fruit buds on primocanes (the first year canes) each year. In other words, there is not a biennial cycle of fruit production.

Primocane-bearing raspberries (red) and blackberries produce fruit for harvest from late summer through fall. After harvest has finished, the canes are removed at the ground level either with pruners or a rotary mower. The next year, new canes that emerge will produce fruit later in the year.

Table grapes are becoming increasingly popular in West Virginia for home gardeners and commercial fruit producers. Like the other fruit crops mentioned, pruning of grape vines is necessary and important for controlling the vigor of the vines so that the plant does not overproduce.

In West Virginia, grapes are pruned in February through early March while the plant is dormant. The objective is to retain a desired number of fruit buds per vine. Most mature grape vines will produce approximately 300 fruit buds, but they will be able to support only 80 to 100 fruit clusters. If the grapevine is not pruned, the plant’s vigor decreases, making the plant more susceptible to diseases. Most of the fruit buds are produced on 1-year-old canes. Older canes are not very productive.

Each year, 1-year-old canes are pruned to approximately three to five buds per cane. The number of buds to retain on each plant depends on the variety. ‘Concord’ – widely grown throughout West Virginia – is pruned to approximately 60 buds per vine. For each pound of 1-year old wood removed from the vine, 30 buds are retained, plus 10 more buds for each additional pound. Once the desired number of buds has been attained, all other 1-year-old canes can be removed. Low-growing and crowded canes can also be removed at this time.

Tree fruits such as apples, pears and peaches are pruned to control growth and improve fruit size and quality. After being planted in the spring or fall, the small apple trees can be pruned to a height of 36 inches and the leader (central trunk) is cut to 18 inches above the uppermost branch. This “heading back” stimulates branch formation, which becomes the future shape of the tree.

The ideal shape for a bearing fruit tree is a cone wider at the bottom than at the top. This shape facilitates light penetration to the canopy. To achieve this shape, prune branches to produce vigorous branches on the lower portion of the tree, with shorter branches farther up the tree. Each year, the upper branches are shortened to keep the cone-shaped appearance. With apple trees, allow the central trunk to grow to a desired height and continually thin the lateral branches to produce a conical shape.

Prune peach and plum trees to produce an open center rather than a central leader. After a young peach or plum tree is planted in the spring, it can be pruned to a height of 30 inches. Topping the young tree stimulates lateral branching. The following winter, leave three to four lateral branches on the tree relatively evenly spaced around the trunk. No lateral branch should be less than 36 inches in height from the ground. The trunk can be headed back to create the open center.

In the summer, water sprouts, which are upright shoots that emerge from the center of the tree, can be pruned out to open the canopy to more light. During the subsequent winter, the outer branches can be pruned to maintain an outward growth by selecting branches that spread away from the center of the tree.

Pruning is one of several practices called “best management practices,” which include cultivar selection, proper fertilization, watering, mulching and pest management. When best management practices are performed, tree and small fruit production will be successful for both home gardeners and commercial growers.

For more information on pruning and other gardening topics, contact your local county office of the WVU Extension Service.