Pruning Gilman

Slide 1 Urban Forest Hurricane Recovery Program http://treesandhurricanes.ifas.ufl.edu Slide 2 Developing a preventive pruning program in your community: Young trees Dr. Ed Gilman and Traci Jo Partin Slide 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 Slide 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 Slide 5 Poor form Good form Principles of strong structure: One dominant trunk Strong branch unions Balanced canopy Slide 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: Slide 7 Collar Strong connection Slide 8 Weak structure: codominant stems and bark inclusions Slide 9 Codominant stems often cause branch failure in storms Slide 10 Failure due to bark inclusion Slide 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 Slide 12 Lions-tailed trees failed Slide 13 Nothing to cut back to should the tree be storm damaged. Slide 14 Notice the large limbs located close to the ground – these will eventually have to be removed for clearance. Slide 15 Big cuts can result in decay and cracks. Slide 16 Low and big cuts can be avoided with early pruning. Slide 17 Structural Pruning Strategies: Develop or maintain a dominant leader Identify lowest branch in the permanent canopy 3. Prevent branches below the permanent canopy from growing too large 4. 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 Slide 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 Slide 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. Slide 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 Slide 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 Slide 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 Slide 23 Impact of pruning dose on co-dominant stem growth before after 75% dose Slide 24 Impact of pruning dose on co-dominant stem growth Foliage removed for 75% dose Slide 25 Slide 26 Slide 27 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 Slide 28 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 Slide 29 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 Slide 30 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: Slide 31 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. Slide 32 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 Slide 33 Bad cut- called a flush cut Wound wood does not develop evenly. Slide 34 Reduction cut Slide 35 Pruning strategies Execution Prioritize which trees to prune Decide location of lowest permanent limbtemporary branch management vs. permanent branch management Slide 36 Prioritize: Structural pruning not as important on these Slide 37 Temporary vs. permanent branch management Keep in mind that all branches will eventually be removed on trees less than 4’’ caliper Slide 38 Temporary vs. permanent branch management Slide 39 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. Slide 40 Reduce growth rate of low aggressive branches Push Push Slide 41 Before After Year two Pushback Slide 42 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. Slide 43 After Before Slide 44 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. Slide 45 Before After Push Slide 46 Two years later Before after Slide 47 Before After Slide 48 Dominant leader structure after two pruning visits Slide 49 Before pruning After pruning Transforming a bush into a tree Slide 50 Two years later Slide 51 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. Slide 52 Slide 53 Reduce growth on branches below permanent canopy Slide 54 2 years later After Slide 55 before after Slide 56 Here is a tree that was damaged in a storm. As a result, many stems are growing upright Slide 57 Remove two upright, interior stems Slide 58 After removing right codominant stem Before Slide 59 Before - year 8 After Debris Slide 60 Before - year 8 After Debris One year after pruning Slide 61 Before - year 8 One year after pruning 18 months after pruning Slide 62 With dedication to a management plan, your community can become a model for others