Principle of apical dominance A naturally occurring plant hormone IAA is produced by the terminal (apical) bud. High concentrations of IAA inhibit the growth of lateral buds. Removing the terminal bud during pruning removes the source of IAA. As the concentration of IAA in the stem decreases lateral buds “break” and push new growth.
Pruning Objectives Reducing the potential for tree or branch failure. Providing clearance. Reducing shade and wind resistance. Maintaining health and structure. Flower or fruit production. Improving visibility. Aesthetics.
A few examples of dysfunctional branches A. Suckers. B. Stubs or broken branches. C. Downward-growing branches. D. Rubbing or crisscrossing branches. E. Shaded interior branches. F. Competing leaders. G. Narrow crotches. H. Whorls.
The collar is formed by overlapping branch and trunk wood. Inside the collar on most trees is a unique barrier called the “branch protection zone”. This zone has chemical and physical properties that retard the spread of decay into the trunk. The presence of a branch collar is a sign of strong branch attachment. Branch collar
A reduction cut reduces the length of a branch or stem back to a live lateral branch large enough to assume apical dominance – this is at least 1/3 the diameter of the cut stem. Click icon to add picture Reduction cut
Use the 3-step pruning cut for larger branches Use for branches that are too big to support with your hand Reduces weight of branch before final cut. 1st cut- up from bottom, 6”12” out 2nd cut-down from top, outside 1st cut 3rd cut- final cut. Near trunk, leaving branch collar intact. 2 1 3
When to prune trees? Remove dead and diseased branches at any time. Live branches are best pruned during the dormant season. A light pruning, removing 10% or less of the foliage, can be performed safely on most species at any time. It is not advised to prune oaks during the growing season.
Shearing involves removing several inches of the current seasons growth flush. Click icon to add picture Shearing is used to create and maintain formal hedges or shape plants. This formal hedge is maintained by shearing
Renovation pruning involves “thinning” a shrub by removing approximately 1/4 1/3 of the stems. Stems selected for removal include older, large diameter stems and any diseased or damaged stems. Heading cuts can also be made to reduce the height of the shrub.
Shrub rejuvenation involves cutting a shrub back nearly to the ground in early spring before growth. This type of pruning is done on old plants that lack vigor and those that have become too large for their location.
Deciduous shrubs that benefit from rejuvenation pruning include shrub dogwoods (Cornus), forsythia (Forsythia), honeysuckle (Lonicera), spirea (Spiraea), some viburnums (Viburnum), weigela (Weigela) and other fast growing ornamentals. Be aware that all plants do not respond to this type of pruning so do a little research before trying this technique. Variegated Willow 3 weeks after a rejuvenation pruning