Pruning Part II - Oregon State University Extension Service

Pruning Part II
Neil Bell/Sam Angima
Extension Agents
Marion & Lincoln Counties
Oregon
Wound paints and dressings

evidence for use is inconclusive

no given treatment fulfills all requirements
1.
2.
3.
Prevent decay
Speed wound closure
Inhibit insect or diseases
Determining time to prune flowering shrubs
=flowering habit
1. Blooms on “old” wood: after flowering
2. Blooms on “new” wood: early spring
The issue is:
When does the shrub form
the flower buds?=last
summer
Camellia
Distinguishing between “old” and “new” wood
Spring blooming shrubs develop buds in fall

Tend to bloom early in season
Summer/fall blooming shrubs form buds as they grow

Tend to bloom later in season
Flowering Quince -spring bloom
Spiraea japonica-summer bloom
Length of bloom period
Spring bloomers: 2 weeks?
Summer bloomers: often more than a month
Rhododendron
Blue Spiraea
Flower type: terminal or axillary
Crabapple (Malus)-winter
Hydrangea paniculata-winter
“New” wood versus “old” wood
Terminal flowers:
Current season wood
i.e. Buddleja
'Ellen's Blue'
(July-September)
Lateral flowers:
One year-old wood
i.e Chaenomeles
Flowering quince
(February-May)
Distinguishing between
“New” wood and “old” wood

Flowering time: spring or summer

Length of flowering period

Axillary or terminal flowers
Some shrubs cause confusion!
(i.e Hydrangea macrophylla)
Genera with species that flower
on both new and old wood
New: Repeat bloomers
Rosa
Hydrangea
Old: Once-blooming, species
New: H. paniculata, H. arborescens
Old: H. macrophylla
Spiraea
New: S. japonica, S. „Bumalda‟
Old:S. x vanhouttei, S. „Arguta‟
Cane growers are easy to identify
Hydrangea macrophylla
Berberis
Pruning Cane growers

Remove:
•
•
•
•

Thin oldest canes
•
Deutzia „Pride of Rochester‟
dead
damaged
crossing
twiggy growth
1-2 per year
Too dense
 thin canes
Too much thinning
 avoid topping canes!
Effects of topping canes (i.e. heading)
Viburnum opulus
Few flowers!
Think about flowering time before pruning!
Cistus x hybridus (Rockrose)
Pruning subshrubs


Buddleia or butterfly bush
if shrub grows throughout
the season
avoid pruning until after
risk of severe freeze

Remove dead stems, prune hard in spring
Lavatera (silver cup): early spring
10 minutes work!
Note where cuts made…
Look how much growth is removed!
Later…
Suckering shrubs
Naturally thicket-forming plants


Rhus typhina (staghorn sumac)
Dig suckers
Use barriers
Pruning Rhododendrons
and Azaleas
Rhododendron stem and bud structure
Prune
above a whorl of
leaves to avoid leaving a stub
correct
incorrect
Pruning Rhododendrons and Azaleas

Removal of spent flowers
promotes branching
Prune after flowering-remove
leading branches at a whorl

Pruning should be done
over a 2-3 year period

The too-big Rhododendron
2. Too big or too dense?
 remove dead wood,
thin branches
5. Turn it into a small tree
 on old, large specimens, remove lower limbs,
dead wood, thin canopy
Pruning Hydrangea
Recall that pruning time will vary with the species!
H. macrophylla
=previous season
H. paniculata
=current season
H. macrophylla:


Remove spent flowers
Thin 1-2 canes
H. paniculata


prune in spring
Cut canes to 2 buds
Remove flower heads
Remove oldest cane(s)
“Hard” pruning of
H. macrophylla
in spring…
=Reduced flower number
Pruning Roses

hybrid tea

climbers
“Once” versus “repeat” flowering
Refers to whether a rose bears flowers on
•
•
one-year-old wood (once-blooming)
current season wood (repeat blossoming)
Once blooming: June
Repeat bloom-all summer
Hybrid Tea, Grandiflora, Floribunda Roses

like all other roses, these are cane growers





remove dead canes
oldest canes may
be cut out
leave 3-4 canes
space around plant
cut back to 18”-2‟
Sucker removal
1. Late summer
3. mid-February
2. Fall
4. mid-February
The final product
Pruning Conifers
For pruning purposes, there are two types:
Needle-like leaves
Whorled branches
Shore pines
Scale-like foliage
Random branches
Junipers
Needle-foliage Conifers: Pine Family
Abies: The Firs
Cedrus: True Cedars
Picea: The Spruces
Pinus: The Pines
Pseudotsuga: Douglasfir
Tsuga: The Hemlocks
When sited correctly, rarely need pruning
Abies pinsapo „Glauca‟
Pinus thunbergii „Thunderhead‟
The biggest mistake: pruning into un-needled growth
Pine Family
To dwarf plant and fill in
canopy, pinch back new
growth at “candle” stage
Do not cut into old, un-needled parts of stem!
Candles on pines are easily broken at this stage
Candle pruning makes a conifer…


dwarfer
bushier
Scale-foliage Conifers: Cypress Family
Calocedrus

Incense Cedar

Hinoki Cypress

Monterey, Italian Cypress
Chamecyparis
Cupressus
X Cupressocyparis leylandii
 Leyland Cypress
Juniperus

many, many species/forms

Arborvitae, Western Redcedar
Thuja
Cypress family plants respond well to
light trimming and make good hedges
Don‟t
prune into
older un-needled
parts of plant!
Effects of hard pruning:
Cutting back hedge
Limbing up too-big shrub
Conifers that respond to cutting to older wood:
Cephalotaxaceae:

Cephalotaxus: Plum yews
Taxaceae

Taxus: Yews
Taxodiaceae
Cunninghamia: Chinese fir
 Cryptomeria: Japanese cedar
 Cunninghamia: Chinese fir
 Metasequoia: Dawn redwood (young plants)
 Sequoia: Redwood
 Taxodium: Bald cypress (young plants)

Brickell and Joyce
DK Publishing, 1996
ISBN 1-56458-331-7
Brown and Kirkham
Timber Press, 2004
ISBN 0-88192-613-2
Cass Turnbull
Sasquatch Books
ISBN 1570613168
Other references:
PlantAmnesty
http://www.plantamnesty.org/

Pruning tips
PNW-International Society of Arboriculture
http://www.pnwisa.org/
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Pruning information
Publications
Lists of Consulting Arborists