You can make a deciduous fruit tree do anything, as long as you understand its growth habit and put the effort in training and pruning the tree, at the correct times.

Newly planted and young trees must be encouraged to make as much shoot growth as possible.

Some shoots are stronger than others, some have different angles than others, and some compete with the main leaders. By directing some of this new growth and getting rid of unwanted shoots in summer, you can make young trees fill their spaces quickly and increase their fruitfulness. Summer pruning also helps in keeping the right tree shape and structure. Most importantly, it keeps the top in balance with the roots.

If you do not direct growth of young trees in summer, you may have to do a great deal of pruning in winter and put up with the costly consequences.

Why is this so?

In summer, roots and tops grow in harmony, which is called the allometric relationship between the roots and the top. The trunk, branches, shoots and leaves represent the top. This simple, universal equation applies to all plants. The roots need the top, and the top needs the roots. But ultimately, the roots control the top. That’s why, for instance, we like to use size-controlling rootstocks (if available).

Pruning young trees in winter upsets the balance between the total root mass and the top of each tree.

In summer, the leaves produce photosynthates, the ‘building blocks’ for growth, in the form of carbohydrates, while the roots take up water and nutrients necessary for the ‘factory’ to produce these building blocks. Leaves and roots also produce hormones, which are chemical compounds produced in minute amounts in one part of the tree and transported to another part where they trigger a response.

In summer, you can direct (influence) growth where you want it, by removing unwanted shoots. The tree will re-direct its growth when and where you want it to go. This is called summer pruning, and can mean shoot rubbing, delay-heading shoots, tipping or stubbing new shoots, making four-finger cuts (peach/nectarine), double-sectorial cuts (apricot) or removing new shoots entirely. Summer pruning maximises canopy growth of young trees and provides the type of wood that makes trees productive quickly and does not cause harmful internal shading.

However, pruning young trees in winter totally changes the tree’s responses from pruning in summer.

In winter, the trees rest. The amount of roots, and the amount of shoots have been determined. You might not like what you see when you prune young trees in winter. When you remove much of the unwanted growth in winter, you upset the allometric relationship.

Putting up with excessive shoot growth is not only expensive, the trees do not like you to remove it. It ‘irritates’ the trees, and they will fight you, until the roots have restored the relationship with the tops during the following season. Unfortunately, the fight usually ends up with more shoots in the wrong places and delays precocity.

Finally, think of bonsai, the old Japanese art of growing miniaturised forms of trees by rigorous pruning of new shoots and roots. The concept of training and pruning fruit trees in an orchard is much the same – if we only could prune the roots as we prune the tops of fruit trees. So, when you want to get rid of unwanted growth, think first of the roots, because roots matter.

*Written by Bas van den Ende from Advanced Horticulture. A Tatura-based author, consultant and former researcher who was involved in pioneering research into managing fruit tree growth and productivity at the Tatura Research Institute, Department of Agriculture Victoria. Contact: advhort@bigpond.net.au