3Principle 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.
6Pruning 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.
23Some important pruning terminology: Branch collarBranch bark ridgeCodominant stemsIncluded bark
24The 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
25A raised area of bark tissue found at the union of a branch and stem. Branch bark ridge
26Two stems with nearly the same diameter originating from the same union. Codominant stems do not form a branch collar and lack a branch protection zone.Codominant stems
27Included bark is bark that has been pinched or embedded between two stems or between a branch and trunk.It is an indication of a weak branch union.Included bark
28More on the “branch protection zone”… From work first done by Dr. Alex Shigo.CODITTrees don’t heal, they seal!
39Use the 3-step pruning cut for larger branches Use for branches that are too big to support with your handReduces weight of branch before final cut.1st cut- up from bottom, 6”-12” out2nd cut-down from top, outside 1st cut3rd cut- final cut. Near trunk, leaving branch collar intact.213
40See what happens when you don’t use the 3-step cut…
41A heading cut also reduces the length of a stem or branch A heading cut also reduces the length of a stem or branch. The cut may be made to a predetermined length or back to a bud.Heading cut
42When 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.
46This formal hedge is maintained by shearing Shearing involves removing several inches of the current seasons growth flush.Shearing is used to create and maintain formal hedges or shape plants.This formal hedge is maintained by shearing
47ShearingBoxwood before shearingBoxwood after shearing
51Renovation 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.
52Renovation pruning Compact Burning Bush prior to renovation Compact Burning Bush after renovation
54Shrub 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.
55Variegated Willow 3 weeks after a rejuvenation pruning 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