7b pruning young trees

Colorado Master Gardener Training

Pruning: Training Young Shade Trees

Training Young Trees

Few cuts are needed.

Training sets the structural integrity of the tree for life!

Gibberellins produced in the root growing tips stimulate growth in the canopy.

Auxins produced in the canopy growing tips

stimulate root growth.

Pruning at planting slows root regeneration.

On new plantings, keep pruning to a minimum until significant canopy growth cycle begins.

Remove damaged & broken branches

Maintain single trunk

1 year / inch of caliper

Overall best pruning time: late winter-early spring

Wound dressings/paints?

Growth habit determines training objectives.

ExcurrentCentral leader trees

DecurrentMultiple scaffold branches

Excurrent (central leader) trees

Pruning objectives to develop structural integrity:

1. Remove broken/problem branches

2. Maintain single trunk to top

3. Establish lowest permanent branch

4. Remove lower branches over time, if desired

Excurrent (central leader) trees Training objective #1

Remove branches that are: Broken or damaged Diseased or dead Competing

Excurrent (central leader) trees Training objective #2

Single trunk

If multiple trunks develop, remove all but one.

If central leader is killed back, start, train a branch as a new central leader.

Excurrent (central leader) trees Training objective #3

Diameter of branches less than 1/2 the diameter of trunk.

Less than 1/3 diameter preferred.

If larger branches develop

1. Remove

2. Prune back to slow growth

Excurrent (central leader) trees Training objective #4

Establish lowest permanent branch

Sidewalk: 7’ to 10’Street: 14’Wooded area: 10”

When pruning-up the trunk, always keep at least 1/2 of the foliage in lower 2/3s of tree.

Pruning up too fastLess trunk taper

Sunscald

Temporary branchesLow vigor (horizontal)Southwest side

branches provide sunscald protection

1/3

1/3

1/3

Training Excurrent (central leader) trees

Excurrent, central leader trees typically need little training and pruning.

Pruning objectives for training excurrent trees

1.2.3.4.

Pruning objectives for training excurrent trees

1. Removed broken, damaged and, competing branches.

2. Maintain single trunk to top.

3. Branches less than 1/2 trunk diameter; less than 1/3 preferred.

4. Select lowest permanent branch, removing temporary branches over time, but before they reach 2” diameter.

Training objectives: Decurrent trees (multiple scaffold branches)

Lack of training when young predisposes decurrent trees to wind and storm damage.

Training objectives: Decurrent trees (multiple scaffold branches)

5 pruning objectives to develop structural integrity for life:1. Remove broken/problem

branches2. Single, dominant trunk well

into tree’s upper region3. Establish lowest permanent

branch4. Select permanent

branches5. Remove temporary branches

over time

Decurrent TreesTraining Objective #1

Remove branches that are: Broken or damaged Diseased or dead Competing

Decurrent TreesTraining Objective #2

Single, dominant trunk well into tree’s upper region

Branches < 1/2 trunk diameter

< 1/3 preferred

Decurrent TreesTraining Objective #3

Establish lowest permanent branch

Sidewalk: 7’ to 10’Street: 14’Wooded area: 10”

When pruning-up the trunk, always keep at least 1/2 of the foliage in lower 2/3s of tree.

Pruning up too fastLess trunk taper

Sunscald

Temporary branchesLow vigor (horizontal)

Southwest side branches provide sunscald protection

1/3

1/3

1/3

Decurrent TreesTraining Objective #4

Select permanent scaffold branches

Branch spacing Crotch Angles Co-dominant trunks/branches Multiple branches at one spot

Potentially permanent branches spaced 6” to 12” apart, moving up and around the trunk.

Branch directly above another: 60” minimum vertical spacing

Branch spacing Mature height > 30’ tall

18” minimum

Mature height < 30’6” minimum

Branches spaced around tree

Multiple branches originating in the same area are structurally weak.

Branch collars can not form completelyBranch defense zone incomplete

This is a natural branching pattern for many trees, (elms, maple, crabapple, flowering plum) predisposing a mature tree to wind and storm damage.

A narrow crotch angle means take a closer look for included bark.

V - Crotch Narrow angle with

included bark = weak

U - CrotchWide angle = strong

Branch bark ridge sticks up in crotch like “mountain range in a valley” = strong attachment

Branch bark ridge disappears in the crotch = weak attachment, may develop included bark

AshAspen

Honeylocust

Ash

Co-dominant leaders (~ equal size) are structurally weak.

Co-dominant leaders develop included bark.

1/2 (1/3 preferred) rule

Correct while smallRemove one leader

Decurrent TreesTraining Objective #5

Remove temporary branches over time, but before they reach 2” (3” maximum) diameter.

Decurrent TreesTraining Objective #5

Temporary branches

Selection Small, less vigorous shoots Prune larger, more

vigorous shoots back to suppress growth

Spacing 4” to 6” minimum >6” from potentially

permanent branches

Pruning objectives for training decurrent trees

1. Remove broken, damaged and competing branches.

2. Maintain single trunk into upper portion of mature tree.

3. Select lowest permanentbranch.

4. Select scaffold branches.

5. Remove temporary branches over time, but before they reach 2” diameter.

Decurrent TreesLateral branches along limbs

Size < 1/2 diameter of parent branch

< 1/3 diameter preferred

Spacing > 24” from trunk > 6” spacing

Ash

Ash

Linden

Crabapple