Hello again, Westside Gardeners.
Most of us think about pruning deciduous stone fruit trees in the winter, but now is an optimal time for tree height reduction.
When deciding which laterals to keep and which ones to remove, keep the laterals of moderate or weak vigor. Overly vigorous laterals tend to grow too long and shade adjacent branches. Their hormonal impulse is to be non-fruiting.
By August and into September, fruit trees have allocated most of their reserves to existing branches, roots and past fruit. The trees are essentially tapped out with inadequate resources to continue pushing new growth.
Additionally, summer pruning of laterals releases ethylene gas at the site of the pruning cut. Ethylene is a gaseous hormone growth stimulant.
The released ethylene gas saturates the tree canopy, particularly the summer-pruned lateral stems. All this helps to stimulate next year’s bud formation rather than vegetative branch extension.
Completely removing upright and vigorous laterals is the best policy. Keep weaker ones growing at an angle approaching horizontal, and train them to grow perpendicular or 90 degrees to the primary branch.
An added benefit of cutting back laterals is that they will be shorter and, thus, thicker and better able to support the weight of the fruit without sagging or breaking. Feel free to contact me if you need further tips on summer pruning.
Mark Koehler of Los Banos is an arborist and master gardener who has degrees in landscape architecture and landscape horticulture from UC Berkeley and Northeastern University. Please send any questions or comments to markgardenguru@gmail.com.
