Pruning Gilman

1. Urban Forest Hurricane Recovery Program

http://treesandhurricanes.ifas.ufl.edu

2. Developing a preventive pruning program in your community: Young trees

Dr. Ed Gilman and Traci Jo Partin

3. Pruning can reduce damage

A recent study at UF showed that pruning reduces the angle of trunk bend when trees are exposed to high winds.

• Not pruned
• Reduction pruning

4. Preventive Pruning: young trees

• Set objectives
• Determine pruning cycle and dose

Execute pruning plan- make good cuts- prioritize trees with structural issues- temporary vs. permanent branch management

5. Poor form

• Good form

Principles of strong structure

• One dominant trunk
• Strong branch unions
• Balanced canopy

6. Objective: Reduce structural issues that cause tree failure

Codominant stems: stems of equal size originating from the same point on the tree

Included bark: bark pinched between two stems, indicating a weak union

Unbalanced canopy:one side much heavier, or most weight at the tips of branches

Large low branches

7. Collar

• Strong connection

8. Weak structure:

• codominant stems and bark inclusions

9. Codominant stems often cause branch failure in storms

10. Failure due to bark inclusion

11. Unbalanced canopy

Lions-tailing: trees with foliage concentrated at the tips of branches because inner branches were removed.

More susceptible to hurricane damage Difficult to restore

12. Lions-tailed trees failed

13. Nothing to cut back to should the tree be storm damaged

Nothing to cut back to should the tree be storm damaged.

14. Notice the large limbs located close to the ground – these will...

Notice the large limbs located close to the ground – these will eventually have to be removed for clearance.

15. Big cuts can result in decay and cracks

Big cuts can result in decay and cracks.

16. Low and big cuts can be avoided with early pruning

Low and big cuts can be avoided with early pruning.

17. Structural Pruning Strategies:

Develop or maintain a dominant leader Identify lowest branch in the permanent canopy

• Prevent branches below the permanent canopy from growing too large
• Space main branches along dominant trunk

Keep all branches less than ½ the trunk diameter

Suppress growth on branches with included bark

Trees require about 25 years of training to develop strong structure.

Objective: Prune to promote strong structure

18. Preventive Pruning: young trees

• Set objectives
• Determine pruning cycle and dose

Execute pruning plan- make good cuts- prioritize trees with structural issues- temporary vs. permanent branch management

19. Pruning cycle: the interval or time between each pruning event

Depends on quality of nursery stock, growth rate, climate, and species.

Should be shorter in warmer climates where trees grow faster.

A longer pruning cycle can lead to larger cuts having to be made to correct structural issues.

20. Determine a pruning cycle

Pruning cycle: - more than 3-5 years = higher pruning dose- every 1-2 years = smaller pruning dose

Suggested program

• At planting- Year two or three- Year five or six- Year ten- Year fifteen

21. Pruning dose: the amount of live tissue removed at one pruning

Depends on customer expectations, the size of the stems, and the pruning cycle.

• Low pruning dose

( < than 20%) Higher pruning dose ( > than 20%) Mature or recently planted trees

Young, established trees Cooler climates with short growing season

Warm climates where trees have longer growing season

• Decay prone species
• Good compartmentalizers

22. Appropriate Pruning Dose for Specific Applications

• Large Pruning Dose
• Small Pruning Dose
• Municipality
• Residences, commercial properties Long pruning cycle
• Short pruning cycle

Aesthetics of less concern Aesthetics are a concern

Effects on the Tree from Applying Pruning Doses Large Pruning Dose

• Small Pruning Dose
• Larger pruning wounds
• Smaller pruning wounds
• Larger void in canopy
• Smaller void in canopy

Greatly encourages growth in unpruned portions of tree

Encourages some growth in unpruned portions of the tree

23. Impact of pruning dose on co-dominant stem growth

• before after 75% dose

24. Impact of pruning dose on co-dominant stem growth

• Foliage removed for 75% dose

25. Maximum critical diameter

Maximum critical diameter: the largest diameter pruning cut you are willing to make on a certain species

This limit should be set for both removal and reduction cuts.

Should be smaller for decay-prone species.

• Is controlled by the pruning cycle

26. Branch size: - proportion relative to trunk - actual diameter of stem

• Branch size
• Consequences of Removal
• Recommended Action

Less than ½ trunk diameter Few consequences Remove if needed

1/3 to ½ trunk diameter Some trunk defects could result

Consider shortening instead More than ½ trunk diameter

• Defects likely

Shorten instead of removing Large enough to have heartwood

• Defects likely
• Shorten instead of removing

27. Preventive Pruning: young trees

• Set objectives
• Determine pruning cycle and dose

Execute pruning plan- make good cuts- prioritize trees with structural issues- temporary vs. permanent branch management

28. Reduction cut shortens the length of a stem by pruning back to...

Reduction cut shortens the length of a stem by pruning back to a smaller limb.

Removal cut prunes a branch back to the trunk or parent branch.

Types of pruning cuts

29. Make good pruning cuts

Step 1 Make an undercut about 12 inches from the trunk.

Step 2 Make a topcut farther out on the limb.

• Step 3

Remove the stub with final cut, being careful not to cut flush against the trunk. Leave the collar intact.

30. Branch bark ridge

Collar: swollen area at the base of the branch where it joins the trunk. The tissue is rich in energy reserves and chemicals that hinder the spread of decay. Good pruning cuts avoid cutting into the collar.

• Collar

31. Bad cut- called a flush cut

Wound wood does not develop evenly.

32. Reduction cut

33. Pruning strategies

• Execution
• Prioritize which trees to prune

Decide location of lowest permanent limbtemporary branch management vs. permanent branch management

34. Prioritize:

Structural pruning not as important on these

35. Temporary vs. permanent branch management

Keep in mind that all branches will eventually be removed on trees less than 4’’ caliper

36. Temporary vs. permanent branch management

37. Pruning Plan: First 5 years

Most branches are temporary.

Do not remove more than 35% of live foliage at a pruning visit.

Reduce all branches greater than ½ trunk diameter.

Reduce and/or remove all branches or stems competing with the one selected to be the leader.

Reduce and/or remove large, low vigorous branches.

Remove broken, cracked or severely damaged branches.

38. Reduce growth rate of low aggressive branches

• Push
• Push

39. Before

• After
• Year two
• Pushback

40. After

• Before

Structural pruning is a three step process

Identify the stem that will make the best leader.

Identify which stems are competing with this leader.

Decide where to shorten these competing stems.

41. After

• Before

42. Pruning Plan: 5 – 20 years

Do not remove more than 25-35% of live foliage.

Reduce all branches greater than ½ trunk diameter.

Identify lowest scaffold limbs of the permanent canopy and reduce all aggressive lower branches.

Reduce branches with included bark.

Reduce or remove competing leaders (if there are more than 3 competing leaders, this can be done in stages).

Reduce branches within 18’’ of largest limbs.

43. Before

• After
• Push

44. Two years later

• Before after

45. Before

• After

46. Dominant leader structure after two pruning visits

47. Before pruning

• After pruning
• Transforming a bush into a tree

48. Two years later

49. Pruning Plan: 20 – 30 years

Identify 5 to 10 permanent scaffold limbs and reduce branches within 18-36’’ to avoid clustered branches.

Space permanent scaffold limbs to reduce wind resistance.

Remove many or all of the branches below the first permanent limb.

Reduce branches with included bark.

Reduce and/or remove competing leaders.

50. Reduce growth on branches below permanent canopy

51. 2 years later

• After

52. before

• after

53. Here is a tree that was damaged in a storm

Here is a tree that was damaged in a storm. As a result, many stems are growing upright

54. Remove two upright, interior stems

55. After removing right codominant stem

• Before

56. Before - year 8

• After
• Debris

57. Before - year 8

• After
• Debris
• One year after pruning

58. Before - year 8

• One year after pruning
• 18 months after pruning

59. With dedication to a management plan, your community can become a model for others

Referenced Links

• http://treesandhurricanes.ifas.ufl.edu