By Ali Sarkhosh
The excessive vegetative growth of low-chill peaches under tropical and subtropical climates can be one of the major problems negatively impacting fruit size and quality. Growers need to spend a significant amount of money and time for manual thinning and pruning to meet the market window.
Factors affecting fruit quality include distribution of light in the canopy, tree training and pruning, crop load, pest and disease control, irrigation and nutrition — all of which are significantly affected by vegetative growth. Due to the more extended growing season for peach trees in subtropical environments and a shorter period of fruit ripening, these factors need to be optimized. Mature trees from about 3 to 10 years of age are usually pruned when dormant (December to February) and during the late spring and summer (May to August).
TRAINING YOUNG TREES
Open center (vase shape) is the recommended training system for Florida. Nursery trees usually have no lateral branches and can be cut back 18 to 24 inches above ground level. Scaffold branches will develop below this cut. These scaffold branches need to be developed low to make pruning, thinning and fruit harvesting operations easily accessible from the ground, or high enough to allow for management practices like weed management, fertilization and irrigation line maintenance.
Nursery trees with greater than a half-inch diameter may have already developed lateral branches. Using pruning shears, remove most of these branches, leaving three to five branches that are evenly spaced in a north, south, east and west direction. During the first spring and summer, trees should be managed to produce as much vegetative growth as possible. Leave major pruning for the winter months when the trees are dormant.
PRUNING IN FIRST YEAR
During the first-year dormant pruning, the task is to select branches that will develop into the main structural branches for a tree with an open center. If this has not been done already, select three to four limbs evenly spaced around the trunk at about a 45-degree angle from the trunk and about 6 inches apart vertically. Prune back these branches 2 to 3 feet from the areas from which the scaffold branches emerged. Leave small shoots along these branches to provide sunburn protection for the scaffold limbs. Remove excessively vigorous upright branches that could interfere with the growth of the scaffold branches.
DORMANT PRUNING IN SECOND YEAR AND LATER
During the second dormant season for peaches, select two to three vigorous lateral branches growing outward from each of the primary scaffold branches. Avoid selecting lateral branches situated on top of each other. Remove other branches and cut back the secondary lateral branches about 20 to 36 inches from the primary scaffold branches. Leave some small branches and twigs, especially on the north and east side of the tree, to provide some shade for the scaffold branches.
The same basic pruning methods are used in the third and fourth dormant seasons. Maintaining an open center in this way will allow light penetration throughout the canopy to stimulate the production of new fruiting wood, improve fruit quality and enable workers to pick fruit without ladders. When dormant pruning, open access to the interior canopy for fruit thinning later in the season needs to be considered. Vertical growth for peach trees should not exceed 7 feet. This allows easy harvest from pickers working from the ground without ladders.
Summer pruning is a management strategy that can be applied soon after harvest, especially in subtropical peach-growing regions, to help restructure the canopy, direct the tree’s resources into fruit production and improve efficiency of fieldwork.
Cut back the tree to a manageable height of 6 to 8 feet. The sides can also be trimmed back 1 to 2 feet to maintain the alleyway width convenient to move equipment through the orchard. This step can be done either by hand pruner, disc pruning or cutter bar machine.
Starting from the ground up, remove suckers coming from the rootstock. Suckers can compete with the scion for water, nutrients and light.
Remove overly vigorous branches that are growing nearly vertical. These branches are referred to as water shoots, which continue growing for much of the season when other lateral branches have slowed growth. Also remove branches that are rubbing or crossing in the middle. Some smaller lateral branches should be left or cut in half to provide shade to the trunk to help prevent bark cracking from sunburn.
Head back branches with excessive blind nodes, which are sections of branches with no visible buds or leaves. Remove any dead branches as well.
- Use clean and sharp tools for pruning to help prevent the spread of disease and make the task more efficient. Loppers are the tool used most often, but hand pruners and hand saws will handle branches if needed.
- After pruning, a fungicide spray application is suggested, if not already part of the summer spray schedule.
- Always keep the tree to a manageable height by topping or cutting off (recommended to be done in summer pruning by disc pruner).
- Old fruiting branches should not be allowed to develop inside the tree canopy.
- Always remove old fruit and dead shoots.
- Always remove strong water shoots inside the canopy. If not required as replacement wood, weak water shoots can be kept to reduce limb sunburn.
- Always remove all the growth, including suckers, within 20 inches of the ground.
- Always remove the secondary laterals that are competing with the scaffold.
- To eliminate some flower buds, remove some laterals or tip laterals over 15 inches by cutting them off about one-third.
Ali Sarkhosh is a University of Florida Institute of Food and Agricultural Sciences assistant professor and Extension specialist in the Horticultural Sciences Department in Gainesville.
This article was featured in the March issue of VSCNews magazine. To receive future issues of VSCNews magazine, click here.
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