3/15/2016
Pruning

What is pruning?

The removal of part of a woody plant for a
specific purpose

The cutting or lopping off of part of a
plant
Pruning
Cindy Collins
OSU Master Gardener
 Why do you prune?
 How do you learn to prune?
 Learn to see your plant
 When do you prune?
 Heading and Thinning cuts
 What will happen and why it
 Pruning Ornamental Plants
 Tools
Outline

◦
◦
◦
◦
happens
Train a plant
◦ Stimulate branching
◦ Select branches
◦ Limit growth
Why do you prune?
Stimulate growth
Remove dead and diseased wood
Reduce disease by increasing light and air flow
Balance the top growth with the root system
Why do you prune?


Improve the health of the plant
Fruit production
◦ Improve fruit size and quality
◦ Train plants so they are more productive
◦ Balance vigor and fruit production
Why do you prune?
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
Aesthetics or Art
◦ Enhance the natural structure
◦ Alter the natural structure
 Topiary
 Hedges
 Bonsai
Why do you prune?
Topiary
Topiary
Hedges
Bonsai
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
A little bit of knowledge

Pick up a pair of loppers
 Make a few cuts
 Watch how your plant responds
 Repeat!
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
Watch an expert
How do you learn to Prune?
Buds classified by their location
 Terminal bud
◦ Located at the tip of a stem
◦ Apical bud
 The terminal bud at the very top of the plant

Axillary bud

Lateral bud
◦ Located in the axil of a leaf
Plant structures you want to identify
◦
◦
◦
◦
◦
◦
◦
◦
◦
Terminal buds and Axillary buds
Latent buds and Resting buds
Flower buds and Vegetative buds
New growth
Branch angle
Relative branch diameter
Branch collar
Past pruning scars
Dead and diseased wood
Learn to see your plant
Buds classified by location
Axillary Bud
Axillary Bud
Axillary Bud
Terminal Bud
(auxin)
A bud that is not a terminal bud
Lateral Bud
Terminal buds and Axillary buds
Buds classified by their status
 Latent bud
◦ A bud that is waiting to be developed
◦ It may wait for years and it may never ‘break’
◦ You may or may not be able to see them

Terminal Bud
(auxin)
Buds classified by status
Resting bud
Resting bud
Resting bud
◦ A bud that was formed at the end of the last
growing season and lies dormant waiting for
growth to start again
Latent buds and Resting buds
Resting bud
Latent Bud
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Buds classified by their function

Flower bud
◦ Blooms and Leaves – Mixed bud
 Pome fruit
Vegetative Bud
Vegetative Bud
◦ Blooms – Reproductive bud (true flower bud)
 Stone fruit

Buds classified by function
Vegetative Bud
Vegetative Bud
Vegetative bud
◦ Leaves and Shoot
◦ Leaves
◦ Latent bud
Flower Bud
Vegetative Bud
Flower buds and Vegetative buds
Flower buds and Vegetative buds
Flower buds and Vegetative buds
Pyrus
Pear
Different color
Different texture
Flowering currant:
Ribes sanguineum
Identify new growth
Bud scars also mark the transition from
old wood to new wood
Identify new growth
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The best angle is between 45 degrees and
60 degrees
◦ Less than this and the branch union will be
weak and prone to breaking
◦ More than this and branch will tend to grow
vertical water sprouts
Strong wide crotch
angle
Narrow weak crotch
angle with bark inclusion
Branch angle
Branch angle
Branch angle
Branch collar

The branch collar contains chemically
protected tissue

Decay will move down a stem until it
reaches this point and then be stopped
and walled off from the rest of the plant
Branch Collar
Relative branch diameter
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
You want to leave branches that are less
than ½ the diameter of the branch they
originate from

If the diameter is larger than this it will
compete with the main branch
◦ Remove these branches
Relative branch diameter
Pruning scars
Easy to see
Winter injury
Dead wood
Broken branches
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Harder to see

Fireblight in pear
◦ Erwinia amlyovora
Don’t look at the color
of the bark
You have to cut and
look at the cambium
layer
Overwintering
canker
Winter injury
Dead wood
Malus
Apple
Diseased wood
Diseased wood
Diseased wood
Where to cut?
Do you feel lucky?
Dying wood
Where to cut?
During growing season:
Infection has probably moved
past the point where you see its
effects.
Cut?
Cut?
Cut?
canker
Cut below canker
Cut below infection
Cut into healthy wood
Cut into previous years wood
Cut into healthy wood
cut
Sterilize tools after every cut!
Cut?


Remove diseased wood
Burn if possible
Remove diseased wood
Burn if possible
Does my plant bloom on new or old wood
or both?
◦
◦
◦
◦
During dormant season:
Infection has probably not
moved past where you see it
Roses
Hydrangea
Berries
Clematis
Does my plant like to be pruned?
◦ Most plants love to be pruned
◦ A few don’t
Other things you want to know
before you cut

When plants are dormant
◦ This is the classic time to prune
◦ November to March
◦ Easy to see plant structure

You can prune in the growing season
◦ After flowering
◦ After harvest
◦ Fine for most ornamentals
When to prune ?
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Cold Weather

◦ Don’t prune at temps below 28 – 32
◦ Plants are more sensitive to cold for about 10
days after they are pruned
◦ Bigger cuts and young plants are more
sensitive
◦ Delay pruning if low temps are forecast to be
really cold.
◦ All pruning should stop at least 5 days before
sub zero temperatures are expected
When to prune?

Insect pest pressure
◦ Pruning during wet weather can make some
plants more susceptible to disease
 Pseudomonas syringae
◦ Favors cool wet conditions
 Bacterial canker of cherry
◦ Some plants don’t really care
◦ Pruning cuts heal over fairly quickly 24-48
hours
When to prune?

◦ Pruning may make a plant more attractive to
insect pests
◦ Time your pruning to minimize this risk
When to prune ?

Two basic cuts
◦ Thinning
 Removal of a branch at the branch collar where it
originates from the parent branch
 Removal of a branch at the base of the plant
Pruning cuts
Effect on vigor
◦ In general the earlier you prune the more you
stimulate growth
◦ The closer you get to flowering and into
flowering the more you slow growth
When to prune?

Stimulates growth and branching

Stiffens the limb and sets position

Reduce the number of flower buds formed
◦ Heading
 Cutting off part of a shoot or a limb
Wet Weather
◦ (new wood)
◦ (old wood)
◦ (new wood)
Heading cut
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Heading cut:
Heading
Cutting above a bud
Heading cut into new wood
Heading
Cut back to a part
that will continue to grow
450 angle
Good!
Too angular Too low
Too high
Alternate-budded plants
Opposite
Heading
45
Limits width
and slows
growth
Branch too small
Angle too big
Redirect and slow
upward growth
Good angle and
branch size
Use to limit the height
of a plant
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
Removal of a branch at the branch collar
where it originates from the parent stem

Removal of a branch at the base of the
plant
Thinning cut

Does not stimulate excessive new growth

Opens up the plant to admit light and air
Thinning cut
Thinning
Removal of the branch at the
place where it originates
Allows you to maintain a plant at a given
height and width for years
 Allows the plant to grow and create side
branches
 You can remove a lot of growth and still
maintain the plants natural appearance
Thinning cut

Thinning Cut
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Shearing
◦ Used for hedges
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Renovation
◦ Removal of all of the plant at its base
Other pruning cuts
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Shearing

Non-selective heading: dense growth at branch tips

Unnatural form, appropriate for formal hedges
Renovation

Cutting all canes back to near
base to renew all growth
Very harsh technique:
not appropriate for
all plants!
This should only be
done when the plant
is dormant
Renovation pruning before
Renovation pruning after

Plant hormones

Apical dominance
◦ Auxins
Questions?
What’s going to happen and why
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Plant Hormones

◦ Work in plants in much the same way that
hormones work in you
◦ Present in very small concentrations in the
plant
◦ Area where a lot of research is done and new
materials called Plant Growth Regulators
(PGR’s) are developed for agriculture
There are 5 Plant Hormones
◦ Auxins
 Most important for pruning
◦ Gibberellins
 Promote stem elongation and flowering
 Delay fruit ripening
◦ Cytokinins
 Promote cell division and growth
◦ Ethylene
 Fruit maturity
◦ ABA (Abcisic Acid)
 Reduces growth during times of stress
 Induces dormancy
Science
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Maintain apical dominance
◦ This causes the main, central stem of the plant
to grow more strongly than side stems

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Maintain dormancy of lateral buds
Geotropism
◦ The effect on the direction of growth with
respect to the force of gravity

Phototropism
◦ The effect on the direction of growth with
respect to a light source
What do Auxins do?
Plant Hormones
The influence of a growing terminal bud
on the buds and shoots below it.
 The terminal bud produces auxins that
move with gravity.
 This chemical message prevents growth of
most lateral buds below the tip and
reduces growth of lower shoots.

Apical Dominance
Under the influence of gravity, auxins
accumulate in the lower side of a
horizontal stem, causing cells to enlarge
faster, turning the stem upright
Apical Dominance
Geotropism
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Geotropism
Phototropism

Where are auxins in the plant?
◦
◦
◦
◦
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Phototropism
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Heading cuts remove the apical bud and
the terminal buds
What happens if you remove
auxins
Apical bud
Terminal bud
Underside of horizontal branches due to gravity
Shady side of a branch
Auxins cause plant cells to elongate
Auxins suppress growth of lateral buds
Lack of Auxin causes lateral buds to grow
and develop shoots
Auxins
Headed back to a renewal point and
thinned one branch
What happens if you don’t remove
auxins
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
Pruning Ornamentals
◦ Goal is to enhance the natural form of the plant
◦ Understand some simple pruning mistakes
Questions about Auxins?
Why I wanted to teach this class
Don’t do this!
This heading cut stimulates branching
Can be used in the first few seasons to train
plants
Do not use it on mature plants
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What is our Goal?
Enhance the natural form of the plant
◦ When does this kind of heading happen in
nature?
 Ice storms
 Wind
 Lightning strikes
Broken branch from ice
storm in a Cottonwood
tree
Removed the terminal
bud which removed the
auxins
Stimulated branching
and growth of the
lower limbs and the
branch itself
◦ What happens?
 Natural form is altered
Why don’t you want to stimulate
branching
Amelanchier x g Autumn Brilliance
Amelanchier x g Autumn Brilliance
Serviceberry
Serviceberry
Amelanchier x g Autumn Brilliance
Serviceberry
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Sambucus racemosa
Red Elderberry
Do this!
Do this!
You can make as many thinning cuts as
you want and you will not distort the
natural growth pattern of the plant
Styrax japonicus
Japanese Snowbell
Limit width
Limit height
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
Big branches at the base of a plant
Smaller and smaller branches as you
move up

‘Cut the big one’

Stewartia pseudocamelia
Japanese stewartia
Maintain this form
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
Thin branches going straight up
Thin branches going straight down
Pruning lateral branches
Instead of trying to decide which branches
to cut…
 Choose the one branch you want to leave
and cut all the rest

The ‘Only one rule’
Saws
Loppers
 Hand pruners
 Hedge Shears
 Hands
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
Questions?
Pruning tools
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Cuts up to 2
inch diameter
branch
Pruning saw
Bypass Loppers
Also good for
cutting back grasses
Cuts ½ inch to 1 inch branches
Bypass hand pruner
Hedge Shears

Sharpening tools
◦ Files
◦ Stones
◦ Special tools

Clean and Lubricate
◦ WD-40
◦ Gun cleaning oil
◦ Fine steel wool
Hands
Caring for your tools
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Sharpening tools
Clean and lubricate
Brickell and Joyce
DK Publishing, 2011
Brown and Kirkham
Timber Press, 2004
ISBN 978-0-7566-7189-1
ISBN 978-1-60469-002-6
Other references:
PlantAmnesty
Cass Turnbull
Sasquatch Books
http://www.plantamnesty.org/home/index.aspx
Pruning tips
ISBN 978-1-57061-751-5
PNW-International Society of Arboriculture
http://www.pnwisa.org/
 Pruning information
 Publications
 Lists of Consulting Arborists
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