The document provides guidance on pruning mature shade trees. It discusses crown cleaning by removing dead, diseased, and broken branches. Crown thinning uses thinning cuts to remove branches under 2 inches in diameter. Crown raising uses pruning cuts to remove lower branches to allow more light in. Crown reduction cuts should be avoided as they can lead to decay. The purpose of pruning should always be considered, and no more than 1/4 of the crown should be removed per year. Topping trees is discouraged as it can structurally compromise the tree.

1. Colorado Master Gardener Training Pruning Mature Shade Trees

2. Prune mature trees with a purpose in mind. Crown cleaning Crown thinning Crown raising Crown reduction Hazard reduction Vista clearance A good pruning job will not be highly noticeable!

3. Prune mature trees with a purpose in mind. Crown Cleaning

5. Prune mature trees with a purpose in mind. Crown Cleaning Removed dead, diseased, and broken branches

6. Why dead branches should be removed: Hazard issues Source of disease organisms or insects Fireblight Cytospora Borers

7. When removing dead branches, do NOT cut into callus tissue.

8. Prune mature trees with a purpose in mind . Crown Thinning

9. Prune mature trees with a purpose in mind . Crown Thinning Use natural target pruning cuts (thinning cuts) Focus on branches <2” diameter

10. Prune mature trees with a purpose in mind . Crown Thinning Use natural target pruning cuts (thinning cuts) Focus on branches <2” diameter A good pruning job will not be highly noticeable!

11. Prune mature trees with a purpose in mind. Crown Raising

12. Prune mature trees with a purpose in mind. Crown Raising Use natural target pruning cuts , pruning to more upright LARGER laterals or remove branch entirely. Avoid reduction cuts to smaller laterals. 1/2 foliage in bottom 2/3s of tree

13. Prune large trees with a purpose in mind. Crown Reduction

14. Prune large trees with a purpose in mind. Crown Reduction Requires reduction cuts Doesn’t protect the branch defense zone Predisposes branch/trunk to internal decay Avoid crown reduction on trees in stress or decline

15. Prune large trees with a purpose in mind. Crown Reduction Begin pruning as tree starts to reach acceptable size, rather than when overgrown. Remove <1/4 of crown-foliage/year

16. Don’t top trees. Topped trees become structurally unsound for life! Branch tissue when it grows with trunk/parent branch Branch tissue from epicormic growth

19. Epicormic shoot

20. Topping > Auxin removal

21. Topping >> the “Don King” look?

22. Prune large trees with a purpose in mind. Hazard Reduction

23. Prune large trees with a purpose in mind. Hazard Reduction Crown cleaning Crown thinning Reduce weight on hazardous limbs

24. Pruning storm damaged trees

25. Pruning storm damaged trees Keep when scaffold branches and trunk have sound wood or can be pruned to sound wood. May accept less than ideal pruning by “mother nature”

26. Pruning storm damaged trees Keep in mind Natural target pruning Structural integrity Heavy pruning required? Select less vigorous shoots May require work over 2-4 years < 1/4 of foliage removed per year

27. Pruning old trees with declining vigor

28. Pruning old trees with declining vigor Focus on Weak and failing branches Lowering crown over time Do NOT “top”

29. Pruning root damaged trees

30. Pruning root damaged trees Prune dead and weak branches Carbohydrate reserves in wood help maintain tree’s vigor Allow natural selection of weak branches Does the tree need crown cleaning or crown thinning?

31. Utility rights-of-way take priority over a tree’s appearance and health.

32. Utility rights-of-way take priority over a tree’s appearance and health. $1 billion / year General arborist 10 feet from 50,000 volt line Line clearance training 15 feet from 552,000 volt line 2 feet from 15,000 volt line

34. Aspen

35. Crabapple

38. How should you prune a mature tree?

39. A tree’s structural integrity is set for life by the training it receives while young.

40. U-prune with laser pointer

41. How did you do?