Pruning
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.
Terminal Bud
Terminal Bud
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.
Tree failure
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.
 B.
 C.
 D.
 E.
 F.
 G.
 H.
Suckers.
Stubs or broken
branches.
Downward-growing
branches.
Rubbing or crisscrossing branches.
Shaded interior
branches.
Competing leaders.
Narrow crotches.
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
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 raised area of bark
tissue found at the union
of a branch and stem.
Branch bark ridge
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.
Codominant stems
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.
Included bark
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.
Types of pruning cuts
 Reduction cut
 Removal cut
 Heading 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.
Reduction cut
Making a reduction cut in the right place
A removal cut removes a
branch from the trunk or
parent branch and is
made to a branch collar.
Removal cut
Making a removal cut in the right place
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
See what happens when you don’t use the 3-step 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.
Heading cut
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
Informal Barberry hedge
Informal Arrowwood Viburnum hedge
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
Shearing
Boxwood before shearing
Boxwood after shearing
Proper hedge shape: it’s all about light
Manual or gas-powered hedge shears
Manual
Gas-powered
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.
Renovation pruning
Compact Burning Bush
prior to renovation
Compact Burning Bush
after renovation
Shrub rejuvenation
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
The End