No matter how necessary pruning is for attaining the desired shape or growth habit of garden trees and shrubs, it is not, as is often assumed, “good” for the plant. In fact, pruning is about as good for the health of plants as surgery is for the health of people. Like surgery, it may be necessary, but there is invariably a price to be paid. There are two ways in which pruning can adversely affect the health of your landscape trees and shrubs.

Firstly, pruning cuts, which are effectively open wounds, are a source of both bacterial and fungal infection. The consequences of infection can take years to become apparent, but eventually, rot is liable to develop in the heart of a tree trunk or major branch. A tree where rot is well advanced is both numbered in years and dangerous.

The second area is more general but no less important for the long-term health of the plant. Pruning is liable to reduce the energy level of the garden trees and shrubs. This may seem counter-intuitive, especially when we see plants growing with renewed vigor following a good pruning. However, the consensus today amongst arboriculturists is that a positive energy level is the single most critical factor behind a plant’s health, vitality, and resistance to pests and disease, and that pruning is detrimental to the plants’ energy level.

This might not be too critical for shrubs, as the lifespan of most landscape bushes, as vibrant and beautiful garden elements, is usually not more than 20-30 years. In other words, by regular pruning, we effectively decide that a compact growth habit or more and better flowers are more important than longevity.

When it comes to trees however, it is a different story entirely, because the greatest value of a tree is in its age. Nothing in gardening compares to or can replace a mature tree. It is a magnificent living sculpture that to a great extent, affects how we feel. It follows then, that care has to be taken to avoid or at least reduce those actions that are liable to affect the long-term health of the tree, and those actions are primarily connected to pruning.

Correct Pruning Cuts – Some Guidelines

*The wound should be as small as possible in relation to the diameter of the trunk or branch to which the removed limb was attached. If the wound is going to be too large, then it is better to leave a stump about 50cm (1.5ft) in length, and periodically cut away new tissue that grows from the pruned branch. In time, the diameter of the limb should be smaller in relation to the girth of the trunk.

*Never make the final cut flush with trunk or branch, as bacteria and fungi are liable to penetrate the tree’s defenses. Studies prove that this occurs even when the wound has calloused over completely. Rot of course, eventually develops from the infection. Instead of flush cuts, prune at the outer border of the joint between the branch and the trunk. The rot that may develop should be contained within this area without penetrating the trunk’s bark.

*In order to prevent infection and reduce energy loss, never remove too much matter at one time. A third of the total volume of the tree is the absolute limit. It is far safer however to stop well before this quantity, and continue the pruning the following year.