Presentation on theme: "PLANT MATERIAL MAINTENANCE Pruning. Both an art and a science."— Presentation transcript:
PLANT MATERIAL MAINTENANCE Pruning
Both an art and a science.
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.
Bud break on Vitis
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.
Pruning for power line clearance
Pruning to reduce wind resistance
The 3-D’s of pruning to maintain tree health and structure Dead Diseased Dysfunctional
A few examples of dysfunctional branches A. Suckers. B. Stubs or broken branches. C. Downward-growing branches. D. Rubbing or criss- crossing branches. E. Shaded interior branches. F. Competing leaders. G. Narrow crotches. H. Whorls.
The desired outcome: a central leader with well-spaced scaffold (lateral) branches
Dormant pruning fruit trees
Espaliered apple trees
Espaliered apple tree trained to grow on the side a house
Pruning for improved visibility
Topiary: An example of pruning for aesthetics
An espaliered Ginkgo tree
Pruning annual and herbaceous perennial plants
Pinching Using your fingers to remove terminal shoot growth.
Deadheading Removing “spent” flowers.
Pruning trees and shrubs
Some important pruning terminology: Branch collar Branch bark ridge Codominant stems Included bark
Branch collar 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 bark ridge A raised area of bark tissue found at the union of a branch and stem.
Codominant stems Two 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.
Included bark Included 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.
More on the “branch protection zone”… From work first done by Dr. Alex Shigo. CODIT Trees don’t heal, they seal!
The anatomy of a 3-year old tree stem
Branch Protection Zone Found in the intact branch collar Chemical changes in the cells seal-off or “compartmentalize” the wounded area
Wound healing will always be more successful when the cut is made at a branch collar.
Reduction cut 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.
Making a reduction cut in the right place
Removal cut A removal cut removes a branch from the trunk or parent branch and is made to a branch collar.
Making a removal cut in the right place
Use for branches that are too big to support with your hand Reduces weight of branch before final cut. 1 st cut- up from bottom, 6”- 12” out 2 nd cut-down from top, outside 1 st cut 3 rd cut- final cut. Near trunk, leaving branch collar intact. Use the 3-step pruning cut for larger branches 123
See what happens when you don’t use the 3-step cut…
Heading cut 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.
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.
Informal Barberry hedge
Informal Arrowwood Viburnum hedge
This 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.
Boxwood before shearing Boxwood after shearing Shearing
Proper hedge shape: it’s all about light
Manual Gas-powered Manual or gas-powered hedge shears
Renovation pruning of shrubs
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.
Compact Burning Bush prior to renovation Compact Burning Bush after renovation Renovation pruning
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.
Variegated 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.