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1/4/2016
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Shrub Pruning
Kathy ZuzekExtension Educator, Horticulture
University of MN
Reasons to Prune Shrubs
1. Remove winter-injured, diseased, dead, crossing, or rubbing stems
2Crossing branches
Winter injury
07/10/2009
Reasons to Prune Shrubs
2. Rejuvenate or renovate old & overgrown shrubs
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10/4/200906/03/2009
Reasons to Prune Shrubs
Reasons to Prune Shrubs:3. Create a unique plant habit: hedge, climbing
plant, espalier.
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Reasons to Prune Shrubs
Reasons to Prune Shrubs:4. Improve stem color
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Reasons to Prune Shrubs
Reasons to Prune Shrubs:5. Increase flower or leaf size and/or intensify leaf
color
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Reasons to Prune Shrubs
6. Reduce or maintain plant size
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Right Plant, Right Space
• Avoid crisis pruning with proper plant spacing at planting time:– Know the dimensions
of your planting space– Choose a plant whose
mature height and width fits that space so you aren’t forced to prune to maintain or reduce plant size
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Tools of the Trade
• Scissors action of bypass pruner is a cleaner, healthier cut than the cut of an anvil pruner
• Used to cut branches up to ½ - ¾” diameter
www.greengate.ca/inthegarden/pruning/equipment.html
Anvil
pubs.caes.uga.edu/caespubs/pubcd/B961.htm
Bypass - Best
Tools of the Trade
• Used to cut branches up to 1 ½”
• Long handle provides leverage & access into center of plant
Pruning & bow saws
• Used to cut branches larger than 1 ½”
Lopping shears
Folding saw
• Long flat blades used to shear hedges or other plants where a neatly trimmed, formal appearance is desire
Tools of the Trade
Hedge shears
Tools of the Trade
• Pruning equipment can spread disease.
• If you are removing diseased wood, disinfect pruning tools between cuts and between plants by soaking/spraying tool in full strength Lysol disinfectant to prevent spread of disease.
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Types of Pruning Cuts
1. Shearing
2. Heading Cuts
3. Thinning Cuts
4. Rejuvenation
5. Renovation
Types of Shrub Pruning Cuts – Shearing
• Used to remove new shoots on coniferous or deciduous shrubs in a formal hedge.
• Clip while new growth is green & succulent to within an inch or so of the last shearing.
• Be sure to prune so the bottom of the hedge is wider than the top. 14
Types of Shrub Pruning Cuts – Heading Cut
• Cutting a shoot or stem back to ¼” above a bud or to its attachment point with another shoot somewhere within a plant canopy.
Back to a bud
Good Bad Bad
Heading cut back to buds: promotes new shoot growth below the cut for a bushier look
plantphys.info/apical/apical.html
When the apical bud is removed, you eliminate the auxin source & lateral buds grow.
Auxin produced in the apical buds suppresses growth of lateral buds
Types of Shrub Pruning Cuts – Heading Cut
• Removal of branches at attachment point: reduces plant size or plant density without affecting plant’s natural shape
Back to another shoot
• Cutting a shoot or stem back to a bud or to its attachment point with another shoot somewhere within a plant canopy
Types of Shrub Pruning Cuts – Heading Cut
• Heading cuts are common on shrubs with only a few main stems (burning bush, witch hazel, rhododendron, conifer shrubs, etc.)
Back to existing shoot
Back to a bud
burning bush
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1) Before pruning 2) Red = heading cuts made w/I plant crown
3) Outward growing branches left 4) Natural habit retained
Graphics Credit: University of Florida
Heading cuts are common on soneconiferous shrubs (arborvitae, yews,
junipers, hemlocks)
Heading cuts are also used to maintain size of an informal hedge
Thinning–Rejuvenation Pruning
In late winter or early spring:• Remove dead stems• Cut the oldest 1/3 of
the main stems (in the center of the plant) back to 3-6” above the ground.
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Reduces plant density and stimulates new stem growth in old shrubs
Restoring bright stem color in a ‘Bud’s Yellow’ dogwood with a rejuvenation cut
4. Heading cuts can be used to reduce height 23
1. Notice older brown branches 2. Removal of older brown older branches
3. New stems will grow from plant crown
Rejuvenation & heading cuts are often combined to manage shrub
size and shape
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Thinning–Renovation Pruning
• The most extreme form of thinning is cutting EVERY stem back to 3-6”.
• Often done on forsythia, weigela, dogwoods and other enormous and fast-growing shrubs.
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10/4/2009
07/10/2009
06/03/2009Removal of every stem to 3-6” to renovate large unhealthy azaleas.
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Pruning Conifers
Pines don’t produce shoots from older wood because:
• they have buds only at branch tips.
• So pruning consists of:
– pruning back to a lateral branch or the main stem.
– Pinching ½ of a “candle” off only in spring to slow the growth rate or produce more branches.
– Anything else will leave a stump with no buds
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Pruning Conifers
• Branches can be removed back to a lateral branch or to the main stem
or
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Spruce, & Fir don’t produce shoots from older wood
buds
Pruning Conifers
• Branch tips can be pruned back to anywhere on the current season’s growth because there are buds all along this growth for next year’s growth.
• Anything else will leave a stump with no buds
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Spruce, & Fir don’t produce shoots from older wood
No buds
buds
Pruning Conifers
• Branches can be removed back to a lateral branch or the main stem.
• Branch tips can be pruned back into 1- or 2-year old wood where dormant buds will generate new foliage
• Anything else will leave a stump with no buds
Arborvitae, Yew, Junipers, Hemlocks
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When should you prune a shrub?
–Minimizes risk of pest problems that infect through fresh wounds
–Plant architecture, defects, and corrective pruning needs are easy to see
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• Mid-summer pruning is also OK if pest problems associated with fresh wounds are not present.
• Dead, diseased, & dying shoots or stems should be removed immediately.
• Other pruning is often done in late winter/ early spring.
Why don’t we prune in autumn ?
Pruning promotes flushes of growth that do not harden off and are susceptible to winter injury.
Growth flush in early fall
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When to Prune Shrubs Grown for Floral Display
• Plants that flower on current year’s wood are usually pruned in late winter or early spring.
• Summer pruning is also OK
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When to Prune Shrubs Grown for Floral Display
Prune plants that flower on previous year’s wood immediately after they bloom.
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•Provides maximum bloom this spring.•New stems with next
year’s flower buds will have time to grow.
When to Prune Shrubs Grown for Floral Display
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1. Shearing or heading• no bloom next
year2. Rejuvenation
• Bloom next year on remaining 2/3 of branches
3. Renovation• No bloom next
year
Results of pruning later in the season after next year’s flower buds have formed:
When to Prune Shrubs
• The bottom 2/3 was sheared in late summer of 2009 to reduce plant width. This also removed flower buds that would have provided bloom in May 2010.
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May, 2010
A lilac that sets flower buds on last year’s wood was pruned inappropriately.
• The upper 1/3 was not pruned, leaving flower buds that produced the 2010 bloom seen in the photo.
