Why Do Fruit Trees Need Pruning? A Detailed Guide to Pruning Time, Methods and Benefits

Fruit tree pruning is a technical measure that involves cutting away part of the tree's vegetative organs to adjust the canopy structure and renew the composition of branch types. But some friends are still not quite clear about why planted fruit trees need pruning, when to prune, how to prune, and what effects pruning has.

Why do planted fruit trees need pruning?

As fruit trees age, their canopies expand, and excessive branches and leaves inevitably lead to a dense exterior and hollow interior, premature tree decline, severe alternate bearing, and reduced fruit yield and quality. Timely and rational pruning can have the following effects:

1. Regulating the reasonable distribution of branches and leaves. That is, on the basis of structural training, adjust the density, distribution direction and leaf area index of branches and leaves in each part of the canopy, so that the effective photosynthetic area of the canopy reaches its maximum.

2. Regulating growth and fruiting. Keep vegetative growth normal without excessive rank growth; produce an appropriate amount of flowers and fruit without weakening tree vigor; at the same time, prevent premature aging of fruit trees and carry out timely renewal and rejuvenation.

3. Regulating the proportion of branch types. Short branches have a short growth period, consume little and accumulate early, but have few leaves and low total photosynthesis; vegetative branches have a long growth period, consume more, but also accumulate more in the later stage. Different tree species and ages require corresponding and appropriate proportions of branch types, so that in the annual growth cycle the transport, distribution, consumption and accumulation of nutrients in the tree can proceed in a coordinated manner according to normal growth and reproductive rhythms. Pruning can achieve this goal.

4. Pruning can also balance the growth vigor among plants in a group and among the main branches of a single plant, thereby achieving balanced yield and facilitating management. In addition, pruning is also a means of coordinating the growth of the aboveground part with the root system.

When should planted fruit trees be pruned?

1. Normal pruning of deciduous fruit trees is carried out during the dormant period from leaf fall to bud break. In cold regions, it is best done before bud break to prevent the cut surfaces from suffering damage during winter; in warm regions, it is best done after leaf fall, because by then nutrients have already flowed back and the wounds can heal within the year. Walnuts need to be pruned after harvest while still in leaf, to avoid bleeding caused by the large pith of the branches. Delayed pruning (that is, pruning after bud swelling) can break apical dominance, increase the sprouting rate, and significantly moderate tree vigor; however, it should not be used year after year, to avoid excessive weakening. For evergreen fruit trees, pruning after harvest or before new shoots sprout in spring is the conventional practice.

2. Pruning carried out during the growing season is generally called summer pruning. Its response is rapid and its effect is strong, and it is mostly used on young trees and vigorous trees to moderate growth vigor and promote flowering, or to regulate the relationship between growth and fruiting. Summer pruning methods include pinching, girdling and branch bending and softening (for deciduous fruit trees), timely “bud removal” and “shoot release” (for citrus), and cutting back and shortening the fruiting mother branches in combination with harvest (such as for persimmon, chestnut and lychee). In addition, plant growth regulators can also be applied to replace some summer pruning measures.

How should planted fruit trees be pruned?

1. Heading back. That is, cutting off part of the shoot segment and buds on a branch, so that nutrients are concentrated and supplied to promote the bud at the cut to be in a dominant position and sprout into a strong branch. Cutting back a perennial branch is also a form of heading back. If a vegetative branch is left below the cut to extend again, it is called “renewal pruning” and serves a rejuvenating function; if no leading branch is left below the cut, it is called “blocking cut”, whose function is to inhibit its growth and often forces it to turn into a branch group. Generally, the heavier the heading back, the stronger the local stimulus to the cut and the part below it, and the more severe the inhibition of the whole plant and even the root system. For example, pruning young trees too heavily often delays fruiting.

2. Pinching. That is, removing the tender portion of a growing new shoot. Its function is to inhibit the continued growth of that branch, direct nutrients to the buds below it or to adjacent parts, and facilitate flower formation or fruit set.

3. Thinning. That is, removing some branches and buds from the base. Because it reduces the nutritional area of the mother branch and creates certain wounds, it can cause the vigor of branches above the thinned part to slow down and that below to become stronger. The effect of thinning on the whole tree varies with the type and amount of branches removed. Removing weak branches, dense branches or water sprouts can reduce useless consumption and increase the effective photosynthetic area, which benefits the overall nutrition; but removing too many vegetative branches will reduce nutrient accumulation and weaken the root system and tree vigor. Operations such as bud removal and shoot removal during the growing season also belong to thinning and are relatively commonly used on evergreen fruit trees.

4. Leaving unpruned. This means not cutting back a vegetative branch but letting it extend naturally, so as to use the weak apical bud to extend, gradually slow down and weaken its apical dominance, increase the sprouting rate of the buds on that branch, promote the production of short branches, and induce flower formation. Leaving unpruned is usually combined with widening the branch angle, and the effect is obvious when the branch grows nearly horizontally or obliquely downward. However, it is generally not used for overly vigorous upright branches on the back.

5. Other methods such as notching, girdling (ring barking), twig twisting or branch bending and softening injure part of the organs or conducting tissues, temporarily changing the direction or speed of nutrient transport, and also have good effects on moderating excessive growth, promoting flower formation and improving fruit set. The application of various pruning methods should be adapted to the tree and local conditions, based not only on the growth and fruiting characteristics of different tree species and cultivars, as well as factors such as rootstock, tree age and tree vigor, but also on the characteristics of natural conditions and the level of cultivation and management. Generally, scaffold branches should maintain vigorous growth; auxiliary branches should have their growth vigor moderated in a timely manner so that they transform into fruiting branches; old and weak branch groups need timely heading back for renewal. When pruning, use the minimum necessary amount of pruning as far as possible, especially for young trees, which should be pruned lightly; at the same time, pay attention to the comprehensive application of various pruning methods and the mutual coordination of winter pruning and summer pruning.

What effects does fruit tree pruning have?

Training and pruning is a core technology in high-quality and high-yield cultivation of fruit trees. Practice has proved that under the same conditions, more than 50% of the benefits from improving fruit tree yield and quality depend on training and pruning techniques. Through summarization, fruit tree training and pruning has seven effects:

1. Through training, make full use of space to build a reasonable tree framework that can bear the high load of fruit;

2. Through training and pruning, continuously maintain ventilation and light penetration within the canopy and improve the photosynthetic efficiency of the branches and leaves in the canopy;

3. Through pruning and training, open up the branching angle of the canopy, weaken vegetative growth, promote flower bud formation and fruit growth, so that fruit trees bear fruit early and produce high-quality fruit;

4. Through training and pruning, continuously cultivate and renew fruiting branches inside the canopy and prevent the fruiting part from moving outward;

5. Through pruning, renew aging main branches and side branches to maintain tree vigor and fruiting capacity;

6. Through pruning, reasonably control fruit yield to achieve high quality and appropriate yield;

7. Through training and pruning, ventilation and light conditions are improved, plants grow robustly, and stress resistance is enhanced.