Post on 05-Mar-2018
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Pruning Ornamental Shrubs and Vines
By Neil Bell Community Horticulturist Marion and Polk Counties
What is pruning?
Timing of pruning
Pruning principles
Specific pruning techniques:
Shrubs Conifers Vines
Why prune?
Frequency of pruning
Pruning references
Contents:
What is Pruning? The selective removal of specific parts of the plant to benefit the whole plant
Corylus avellana ‘Contorta’
Pruning is NOT: a way to compensate for inappropriate plant placement!
Plant placement
Consider the mature size of plants and available space
A couple of exceptions…
Coppicing Subshrubs
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Why Prune? Develop unusual forms
Remove dead, diseased or broken parts
Prune out winter injury
Removal of reverted growths
Euonymus
Buxus
Sucker removal
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Shape the plant: directing growth
Rosa ‘Eddie’s Jewel’
Size Control: short term only!
Why Prune at all?
Pruning is a stress on plants
March June
is that really desirable?
Plant will grow unassisted to natural form
Timing of Pruning
1. Flowering habit
Blossoms on old wood Blossoms on new wood
Depends on:
Viburnum plicatum Phygelius
2. Objectives remove dead wood anytime
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3. Risk of winter injury Fuchsia, Hebe, Salvia etc.
Salvia desoleana
4. Convenience…
Philadelphus lewisii
Frequency of Pruning
1. Prune only as needed
Growth habit will influence pruning requirement
2. Type of plant clipped hedges
3. Need for size control maybe not practical!
Know the plant and keep a good reference around…
Witch hazel (Hamamelis x intermedia)
observe growth/flowering
observe the response to cuts
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Most importantly: learn what your pruning will do! Principles of Pruning
Directing growth
Adaptations to damage and disease
Growth of woody plants
Principal pruning cuts
Growth habit of woody plants
Lilac: Syringa vulgaris Spring 2014
Growth resumes at shoot tip
Not all buds develop
Twig diameter increases with age
2013
2012
2011
2010
2009 Shoot length decreases yearly
color change in wood
Flowering currant: Ribes sanguineum
Terminal Bud (auxin)
Axillary Bud
Flower Bud
Latent Bud
Parts of a branch
Node
Cherry Laurel (Prunus laurocerasus)
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Flower buds/flowers/fruit are for one season only…
Serviceberry (Saskatoon): Amelanchier alnifolia
Vegetative buds live indefinitely…
450 angle
Good!
Too angular Too low Too high
Directing growth:
Alternate-budded plants Opposite
Cutting above a bud
Response to pruning
removing terminal bud
allows lateral development
topmost remaining bud grows most strongly
alternate opposite
removal of material causes growth elsewhere
Another way to force branching… Cutting back branches
Cut back always to a part that will continue to grow
At least ½ the size of the part being removed
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Pruning cuts Thinning removal of entire stem or section of stem
opens up the plant to admit light
reduces overall height and promotes regrowth
Thinning cut
Philadelphus lewisii
Heading (selective)
Cutting back to a bud or shoot
Promotes branching, will “fill in” the plant
Heading cut
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Shearing
Non-selective heading: dense growth at branch tips
Unnatural form, appropriate for formal hedges
Thinning
Heading
Pinching
Heading, Thinning and “Pinching”
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Enhance a characteristic: Coppicing
Shrub dogwood (Cornus sanguinea) C. sanguinea ‘Midwinter Fire’
Annual hard pruning preserves cane color, reduces size
Coppicing:from the French “to cut”
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Coppicing to enhance leaf size… Cotinus coggygria (smokebush)
Renovation
Cutting all canes back to near base to renew all growth
Very harsh technique: not appropriate for all plants!
February, 2009
April, 2009
January, 2010
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Adaptations to damage and disease
Plants have no “wound healing” process: healing in a sense of replacing or repairing injured tissues.
Plants seal off damaged tissue rather than heal it.
CODIT Compartmentalization Of Decay In Trees
Plants are highly ordered, compartmented Instead of healing, plants compartmentalize
injured and infected tissues.
callus tissue is produced on the wound margin Wound paints and dressings
evidence for use is inconclusive
no given treatment fulfills all requirements
1. Prevent decay
2. Speed wound closure
3. Inhibit insect or diseases
http://pnwhandbooks.org/plantdisease/pesticide-articles/tree-wound-paints
Further reading from the PNW Disease Management Handbook:
When and how to prune a shrub depends on…
1. Flowering habit 2. Growth habit
Calycanthus x raulstonii
Pruning Shrubs
Rosa sp.
1. Blooms on “old” wood:
Determining time to prune flowering shrubs The “flowering habit”
2. Blooms on “new” wood:
The issue is:
When does the shrub form the flower buds?
after flowering
early spring
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Flowering Quince (Chaenomeles sp.)
Spring blooming shrubs develop buds in fall Tend to bloom early in season
Distinguishing between “old” and “new” wood Summer/fall blooming shrubs form buds as they grow Tend to bloom later in season
Japanese Spiraea (Spiraea japonica)
Stachyurus praecox ‘Variegata’
“Current season” versus “previous season” growth Length of bloom period
Rhododendron
Spring bloomers: 2 weeks?
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Fuchsia magellanica
Summer bloomers: often more than a month Flower type: terminal or axillary
Fuchsia-flowered gooseberry (Ribes speciosum)
Axillary
Terminal flowers
Hydrangea paniculata
Terminal flowers: Current season wood i.e. Buddleja (July-September)
Lateral flowers: One year-old wood i.e Chaenomeles (February-May)
“New” wood versus “old” wood
Some shrubs cause confusion!
Hydrangea macrophylla Hydrangea macrophylla Endless Summer™
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Genera with species that flower
on both new and old wood
Rosa
New: Repeat bloomers
Old: Once-blooming, species
Hydrangea New: H. paniculata, H. arborescens
Old: H. macrophylla
Spiraea New: S. japonica, S. ‘Bumalda’
Old: S. x vanhouttei, S. ‘Arguta’
How to prune: depends on growth habit
Cane growers: i.e. Philadelphus
Permanent framework: i.e. Rhododendron Subshrub: i.e Perovskia
Cane growers are easy to identify
Hydrangea macrophylla
Cane growers
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Deutzia sp.
“Cane” growers
Deutzia Forsythia Hydrangea (Mophead etc.) Kolkwitzia (Beautybush) Philadelphus (Mock orange) Physocarpus (Ninebark) Ribes (Currant/Gooseberry) Sambucus (Elderberry) Spiraea (“Bridal Wreath”) Rosa (Rose) Viburnum Weigela
Permanent framework
Have a “tree-like” structure
Do not renew themselves from the base Often are evergreen shrubs
Pieris japonica Rosmarinus officinalis ‘Arp’
Permanent Framework
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Hebe ‘Red Edge’
Arctostaphylos (Manzanita) Ceanothus (Wild lilac) Cistus (Rockrose) Daphne Hamamelis (Witchhazel) Hebe Hibiscus (Rose of Sharon) Ilex (Holly) Lavandula (Lavender) Pieris (Andromeda) Rhododendron (and azalea) Rosmarinus (Rosemary)
Permanent Framework
Arctostaphylos catalinae
Some are deciduous…
Hamamelis (witchhazel)
Hibiscus syriacus (Rose of Sharon)
Subshrubs
Salvia microphylla Phygelius ‘Sensation’
Have a woody framework Produce flowers on new growth
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Artemesia sp.
Vitex agnus-castus
Artemisia (Wormwood) Caryopteris (Bluebeard) Ceratostigma (Plumbago) Fuchsia magellanica (etc) Gaura lindheimeri Heptacodium (7 Sons Plant) Hydrangea paniculata Lavatera (Tree mallow) Salvia (Sage) Perovskia (Russian sage) Penstemon Phygelius (Cape Fuchsia) Vitex (Chaste tree) Zaushneria (California Fuchsia)
Some examples of subshrubs
Lavatera spp.
Pruning Cane growers
Deutzia ‘Pride of Rochester’
Remove: • dead • damaged • crossing • twiggy growth
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Year 1 Year 2 Year 3 Deutzia ‘Pride of Rochester’
Deutzia scabra “Limbing up”
Shearing cane growers