Pruning is not good for plants. Contrary to what is believed, pruning plants is not necessary to ensure their well-being and prevent them from getting sick.
Plants that grow in their natural state in fact live much longer than plants that are instead subjected to maintenance by man, especially if these are carried out ignoring the needs of the plants and their defense mechanisms.
So pruning is bad for plants, it must be performed only in case of need and in any case taking into account the physiology of trees and shrubs.
Why pruning stresses plants
There are at least three reasons why pruning ages and stresses plants and trees.
The first reason is the removal of the leaves. Although pruning is carried out in winter when the deciduous plants have no leaves, in reality by removing the branches we also eliminate the buds from which the new foliage will sprout in spring.
A pruned plant will therefore have fewer leaves from which to draw its nourishment through photosynthesis, with the consequent difficulties given by the lack of nourishment that this entails. This explains why drastically pruned plants have much larger than normal foliage: it is the plant’s attempt to increase the photosynthesizing surface with larger leaves since they are in smaller numbers.
In addition, eliminating branches and branches also eliminates the reserves of the tree accumulated in the form of starch in the wood that is removed.
A second reason is given by the fact that the removal of the branches always involves the consequent suffering of the root system. In fact, there is a direct correspondence between the foliage and the roots. Each branch supplies complex sugars produced in the leaves to a group of roots and, vice versa, each group of roots supplies a specific branch with mineral elements and water. Following the cutting of some branches then, the corresponding roots will find themselves deprived of their source of livelihood and will perish.
The third and perhaps most important reason why pruning weakens the plant is given by the need to close every cut inflicted by us, in order to avoid the entry of pathogens and in particular of cariogenic fungi inside the wood. The plant reacts by isolating each wound, building around it a protective barrier that isolates it from the rest of the body.
This has to do with the protection mechanisms that plant elements put in place to be able to defend themselves without being able to move.
In fact, all the vital functions in plants are distributed, so damaging a part of their organism will not determine their death, as instead happens to animals if a certain organ is irreparably damaged.
In fact, plants can be defined as compartmentalized organisms with continuous growth.
They cannot regenerate damaged tissues, as is the case with animals. However, they can isolate them from the rest of their organism along with the pathogens that have attacked them: this is why they are called compartmentalized organisms.
This defense mechanism can be understood by taking the example of a submarine, whose watertight compartments isolate any leaks created in the hull. In the same way, the plant reacts to attacks by creating barriers that separate the damaged part from the rest of the body, preventing pests from spreading inside them.
Plants can also create new parts of their organism to replace the now abandoned ones, hence the definition of continuously growing beings. Through the generation of new parts, a plant can be assimilated more to a colony of organisms than to a unitary organism as in the case of animals. Therefore, the modular set of relatively autonomous parts means that the plant is a multi-being with a virtually unlimited lifespan.
There are four types of barriers that are created to contain a pathogen.
The first prevents parasites from moving vertically, occluding the vessels through which the lymph normally flows.
The second and third barriers prevent movement in the radial and tangential direction inside the trunk and branches, thanks to the production of repellent and hardening substances such as tannins. That is, the wood is impregnated with substances harmful to pests, isolated and left to die.
The last barrier, the most effective, is the one formed by the plant outside: gradually a healing callus is formed that closes the wound from the edges to the center, thus completing the fragmentation of the attached area.
Over time, therefore, the damaged area now completely isolated, will remain inside the trunk of the plant and left aside. But this should not be misleading: the containment of pathogens does not imply their destruction (plants do not have an immune system that can generate antibodies) and the isolation of the damaged area does not mean its healing.
So it is always a good idea to avoid causing injuries and trauma to plants.
To activate the protective barriers at its disposal, the plant must obviously use energy.
Young plants will therefore react more readily than mature ones, and healthy plants will be able to defend themselves better than others already weakened by previous attacks.
For this reason, in general, young plants will tolerate more marked pruning interventions, while senescent plants will have difficulty withstanding even limited pruning. In any case, under normal conditions the pruning of an adult tree in good vegetative conditions should not remove more than 30% of the total leaf surface.
An extreme case: the capitulation
All this does not mean that a plant should never be pruned. It can be pruned if there are precise reasons to do so, such as to stimulate fruit production in agriculture, or for aesthetic reasons such as inducing a second flowering.
However, we must know in any case that with pruning we are causing the plant a suffering that it would gladly do without.
This is especially true in the case of capitulation.
Capitulation is a drastic pruning that removes all the crown of a tree, leaving intact only the trunk and the main branches. The capitulated plant will then be completely bare and will have large wounds at the removed branches of greater diameter.
The damage caused by the capitulation is multiple and serious.
First of all, the capitulated plant is irreparably disfigured from an aesthetic point of view. No matter how hard we try to restore balance and harmony, we will never be able to restore its original bearing.
Then, the extensive wounds caused will constitute a preferential access route for very dangerous pathogens, such as fungi that are the cause of wood caries. In fact, the plant will not be able to close too extensive cuts, thus allowing the cariogenic fungi to penetrate inside the trunk and branches and to begin their inexorable work of disintegration of the wood. This will cause over time deep cavities inside the tree, which will seriously affect its future stability up to the drastic removal for safety reasons.
The plant that has undergone a capitulation, will then have to make full use of all its energy reserves to close the cuts and give life to a large amount of new branches and leaves, necessary for its survival. So, contrary to the chatter propagated by incompetent people, some of whom unfortunately are insiders, the great liveliness with which a capitulated tree gives life to new leaves is not proof of the invigorating effect of drastic pruning, but is the sign of the desperate attempt of the plant to reconstitute a leaf surface sufficient to keep it alive.
A capitulated plant will therefore be weakened and more prone to the onset of other diseases, until it sinks into an inexorable spiral of decay.
Finally, the numerous branches emitted, commonly called ‘scopazzi’, will largely originate from adventitious buds to which the plant resorts in cases of extreme necessity.
They will therefore be grafted on the main branches in a very superficial way so that, once grown up, they will constantly be at risk of falling. It is this the first cause of the frequent falls of branches from the trees, especially in our cities.
So a capitulated plant will be in practice irrecoverable from an aesthetic point of view, it will be weakened and will need interventions aimed at avoiding falling branches throughout its life.
So the capitulation, as often happens for practices that allow to achieve immediate savings, turns out to be actually a source of problems, with risks and very high costs in the medium term, as well as being the main cause of impoverishment of our plant heritage.
How to prune plants in the garden
Once we have understood that pruning is in any case a traumatic intervention for the plant, we can ask ourselves how to prune the plants if this is required.
First we can distinguish two main types of pruning on the basis of the period in which it is carried out: summer pruning and winter pruning.
During the summer, in the months of July and August, it is possible to practice the so-called green pruning.
Green pruning consists in removing the scions and the suckers, or the new shoots at the base of the trunk, along it and in the center of the crown of the plant, the ones that are still green or that have not yet lignified.
Carrying out the green pruning will ensure that then, when we go to carry out the main pruning at the end of winter, we will have much less vegetation to remove and therefore the plant will suffer less stress.
In addition, summer is the ideal time to prune plants sensitive to cuts.
Although in the warmer months they are in vegetative rest, in summer the plants are at the maximum of their energy level.
In fact, they are coming from the spring period in which photosynthesis takes place very effectively and allows a surplus in the production of complex sugars compared to the vital needs of their metabolism.
In these months they will therefore have reserves to devote to closing the cuts without compromising their energy balance.
In addition, the vegetative recovery of autumn allows them to immediately start the mechanisms that lead to the creation of protective barriers without having to wait two or three months. This means that, for plants that struggle to close the wounds such as all the stone fruits (peaches, plums, apricots, etc.), summer is the best time to go pruning.
The end of winter is, however, in general, the most suitable time for pruning since the plants are in their period of maximum vegetative rest.
The first precaution to have, is to prune only at the end of winter, when the most intense colds have now passed. In fact, too early pruning, especially in the case of rather mild winters as happens more and more frequently, can have the effect of stimulating the re-entry of new shoots by the plant, with the risk that late frosts can then seriously damage it.
But how should you prune?
First of all, you should never make drastic pruning, to avoid putting the health of the plant at risk as well as removing branches that would have given life to new flowers in spring.
In fact, it must be known that there are plants that bloom on the branches emitted during the same season and therefore require less care, plants that bloom on the branches of the previous year and others that bloom on the branches of two or more years.
So, by pruning in excess and in the same way all the plants, we will certainly remove branches that would have generated the flowering we wanted.
However, it is not easy, if not for experts, to know all the plants and their flowering mode as well as the age of the various branches.
It is therefore a good idea to limit pruning to targeted interventions and, regardless of the type of plant, to be able to recognize the difference between flowering buds and wood buds.
The flowering buds are fuller and rounded, and will give life in spring to leaves and flowers, which will then turn into fruits.
The wood buds, on the other hand, are narrower since they do not contain the flower in embryo and will only give life to leaves and branches. Knowing how to distinguish between the two types of buds will therefore allow us to leave the flowering ones so as not to affect the flowering or the production of fruits, and remove only portions of branches that have wooden buds.
So by learning to observe the plants and respecting them with delicate interventions, everyone can be able to prune and care for the plant elements of the garden without damaging them.