De’Anthony Price, UF/IFAS Extension Jefferson County, Ag & Natural Resources Agent
Pruning is known to be a beneficial cultural practice for blueberry production. Pruning requires skills, and growers typically create their signature technique, which may differ slightly from their neighbor’s, but should accomplish the same objectives. This article discusses some basic principles of pruning and provides a few suggestions and observations which may help determine how and when to prune blueberries in Florida.
Pruning benefits blueberry production in several ways:
- Balances the top with the root system and limits fruit production
- Aids in development of desirable plant size and shapes that facilitate other cultural practices
- Increases plant growth of new fruiting wood
- Decreases the spread of certain diseases and helps control some pests
- Prevents over-fruiting and enhances fruit size, quality, and earliness
- Improves sunlight penetration into the interior and lower portions of the canopy
There are two basic types of pruning cuts commonly used in blueberries. Each type of pruning cut results in a different growth response and has various purposes.
Heading-back cuts which consist of cutting the terminal of a shoot back to a lateral bud, usually on one-year-old wood. Heading-back cuts stimulate the growth of the lateral vegetative buds along the shoot, usually just below the cut. Heading-back cuts are used to control bush height and width, promote the development of new fruiting wood, and adjust crop load. This type of pruning may be done mechanically or by hand.
Thinning-out cuts which consists of complete removal of a shoot or cane at or near its origin. The thinning method removes older, less productive canes and rejuvenates bushes through increased production of new canes. Thinning also decreases dense canopies, allowing for better air circulation and light and spray penetration. Thinning is usually done with hand loppers, pneumatic loppers, or pruning saws.
Pruning During Plant Establishment
When transplanting them to the field, the goal is to remove 1/3 to 1/2 of the top of young blueberry plants. Remove weak, twiggy growth near the base of the plant and side branches bearing flower buds. All flower buds should be removed by pruning or rubbing off during the first year. Removing flower buds from young plants can increase canopy growth and plant establishment. Containerized plants that are not pot-bound and are provided with overhead or micro-sprinkler irrigation may not need any pruning at planting except to remove flower buds. For 2-year-old plants, remove weak, twiggy, growth, and damaged or diseased wood, and continue to remove flowers from vulnerable plants and non-vigorous cultivars. Pruning should be done during the winter, before flowering and fruit set. During the first two to three years, the goal is to promote canopy establishment through vegetative growth and to develop correctly shaped plants for maximum fruit production. Mechanically harvested rabbit eye plants should be kept narrow at the base (18 inches or less). Remove all side branches below 18 inches in the second and third years.
Pruning Southern High Bush
Annual dormant pruning of highbush blueberry plants is needed to reduce fruit quantity, maintain plant growth, and enhance fruit quality and earliness. Dormant pruning should be done during the late winter when flower buds are readily visible and should be done before petals fall. Fruiting canes should be headed back, if fruit load reduction is needed. This is important for varieties that set large numbers of flower buds and leaf poorly during the spring. Removing low-spreading branches and weak, twiggy growth in the lower parts of the plant can be done at this time. More severe pruning will be required in vulnerable and less vigorous plants. Extremely strong one-year-old shoots should be headed-back to stimulate lateral branch development. The goal is to control fruit load, increase next year’s crop growth, and maintain proper plant size and shape. For plants five to six years old and older, cane renewal is one of the main objectives of pruning. Individual blueberry canes aged 5 to 7 years old become increasingly branched and twiggy and lose their productivity. The older canes should be removed when blueberry plants are between 5 and 6 years old. This will increase the development of new, productive canes. Each year, thinning cuts remove approximately 25% of the oldest canes by cutting them back to solid laterals or close to the ground. Regular cane renewal pruning allows for constant long-term productivity with bushes that contain a mixture of canes of different ages. As plants age, thinning cuts and heading-back cuts will be needed for cane renewal, fruit load adjustment, maintenance of vigor, and proper plant size and shape.
In Florida, summer topping increases vegetative growth of bearing southern highbush and should be done soon after harvest, usually during June. Plants should be fertilized the week before pruning so they will renew vegetative growth quickly after pruning. Delaying summer topping can delay bloom and fruit harvest the following year. Post-harvest pruning stimulates new summer growth with leaves that remain healthy longer and abscise later during the fall than spring flush leaves. The summer growth flush following the topping will contain many flower buds for next year’s crop. Some observations indicate that summer pruning every other year increases yields to annual pruning. Some growers have devised mechanical hedgers, which are mounted on tractors and can be used to mow the tops of the plants about 40 inches above the ground. Light-weight gasoline-powered hand-held hedge pruners are also available, which can be used to cut the tops off the plants after harvest. These are far faster than hand loppers and can be used to thin the bush canopy and remove the plants’ tops.
Pruning Bearing Rabbiteye
The goal for pruning bearing rabbiteye plants is the same as for southern highbush with a few changes. More attention should be given to narrowing the base of plants where mechanical harvesting is desired. Rabbiteye plants typically get larger and more vigorous than southern highbush. As plants reach bearing age, plant height should be controlled. Rabbiteye plants are more vigorous and less prone to overbearing than southern highbush plants. As rabbiteye plants reach five or more years old, selective hand pruning for cane renewal is important. Annual removal of 20% to 25% of the oldest canes before initiation of spring growth will increase new canes and should result in plants with canes of different ages and a desirable balance of vigor and fruit production. Moderate summer pruning may be combined with selective cane removal on early ripening rabbit eyes in Florida. Other vigorous canes growing from the ground can be topped to increase branching and flower bud formation. Light mechanical topping after harvest (July) can help maintain canopy height for mechanical or hand harvesting. Mechanical topping does not remove deadwood from the bush interior nor allows for rejuvenation of the bush. If mechanical pruning is used, some hand pruning will also be needed.
Rejuvenation of Rabbiteye
Plant Rejuvenation, or renewal pruning of rabbiteye blueberry plants can be conducting using a few methods. Bushes can be hedged at one to two feet during the winter or summer, but this will decrease yields for one or two years following pruning. The plants are about four feet tall two years after pruning and flower heavily. This type of pruning should only be used on plants that have become unproductive through neglected pruning practices. When rejuvenating an entire field, growers may want to consider severe renewal pruning on only a portion of their planting during a given year to maintain some level of fruit production during the rejuvenation process.
For more information
- Tips for Transitioning to an Organic Cropping System: Soil Health - March 1, 2024
- 2024 Small Fruit Seminar & Field Demo – February 20 - January 12, 2024
- Jefferson County 2024 Beginning Beekeeping Series:January 13-February 10 - December 20, 2023