Tree Maintenance Practices

Transcription

1 OUTLINE. I. Pruning Methods a. Crown Raising.3 b. Structural Pruning...3 c. Thinning 4 d. Crown Reduction (drop crotch).4 e. Restoration...5 II. Pruning Cuts a. Types of Pruning Cuts.5-8 b. Principles, Reasons & What to Prune..9 c. Proper Pruning Cuts III. Timing a. When to Prune.11 b. Tree Health Effects of Pruning at the Wrong Time 11 IV. Tree Types a. Conifers (evergreens).12 b. Hardwoods (deciduous)..13 c. Age class...14 d. Urban & Rural V. Tree Health and Structure a. How Pruning Affects Tree Growth..16 b. Wounds and Sealing.17 c. Tree Protection and Common Pruning Injuries

2 VI. Sight Distance & Clearance Standards a. Road and Sidewalk Clearance Standards 19 b. Proper Sight Distance Standards...20 c. Structural Conflicts 20 VII. Common Tree Hazards a. Common Tree Hazards 21 b. Signs of Disease

3 I. Pruning Methods: a. Crown Raising. Raising is the selective removal of branches to provide vertical clearance. When crown raising it is important not to remove to many lower branches. This can cause slow development of trunk taper, cause cracks or decay in the trunk, or transfer to much weight to the top of the tree. Prune no more than 30% of the living branches in a season, and no more than 10% from mature trees. Remove only what is necessary for clearance and safety. Remove hazardous, diseased or dead branches first. Remove lowest branches to prescribed height for appropriate clearance needs. Crown Raising b. Structural Pruning Utilized when the primary objective is to maintain or improve tree health and structure, and includes hazard reduction pruning. Structural pruning aims to remove defects, improper growth, diseased limbs and dead material from the tree to promote proper growth and structure. Remove structural defects to reduce hazards. Remove dead, diseased, dead and dying branches. Remove water-sprouts and epicormic shoots. Prune limbs and branches to promote proper tree growth and structure. Promote balance and proper crown structure. Structural Pruning Proper Structural Pruning Removal of Gray shaded limbs 1. Branch Stubs 2. Rubbing/crossing limbs 3. Water sprouts 4. Suckers 5. Closely spaced branch 6. Weak, narrow crotch 3

4 c. Thinning Consists of the selective removal of branches to increase light penetration, air movement and reduce overall crown weight. This type of pruning removes entire branches or shoots to stimulate more vigorous growth of the remaining branches. When done properly, the natural shape of the tree is maintained. Favor branches with strong, U-shaped angles of attachment. Remove branches with weak, V-shaped angles of attachment and/or included bark. Lateral branches should be evenly spaced on the main stem. Do not remove over 30% of the living crown of a tree at one time from young trees, and no more than 10% from mature trees. Make sure lateral branches are no more than ½ to ¾ of the diameter of the main stem, to discourage the development of co-dominant stems. Original Tree First Pruning Second Pruning d. Crown Reduction / Crown Shaping This pruning method aims to decrease the height and/or spread of a tree. This type of pruning is done to minimize the risk of failure, to reduce the height or spread, for safety, road and utility clearance, sight distance, and to clear vegetation from structures. Prune with reduction cuts and not heading cuts. Remove only limbs necessary to accomplish desired need. Promote tree balance and structure. Never remove more than ¼ of the living crown. Do not top trees, cut back to lateral branch attachment(s). Leave Apical dominance. Proper Reduction Pruning 4

5 e. Restoration Restoration pruning should improve the structure, form and appearance of trees that have been damaged by storm events, mechanical injury, vandalism or other improper pruning techniques. The goal of this pruning is to reduce hazards and restore proper tree growth and structure. Assess tree damage and locate potential hazards. Remove damaged or injured branches/limbs that could be a hazard. Prune to restore tree balance and structure. Remove dead, diseased and dying branches/limbs. Damaged limb Dead branch Large crack Remove potential hazards Remove dead limbs Assess tree damage II. Pruning Cuts: Proper Pruning Cut Standards Pruning cuts shall be made in branch tissue just outside the branch bark ridge collar, without causing injury to the tree. No flush cuts shall be made. No stubs shall be left on the tree. Cuts shall have no ripping or tearing of the bark. a. Types of Pruning Cuts I. Three-Cut Method. II. Drop Crotch Cuts. III. Collar cuts vs. Flush Cuts. IV. Stub & Deadwood Cuts. V. Tip Pruning. 5

6 I. Three-Cut Method The three-cut method is used when pruning live branches over 1cm in diameter. The method is utilized to prevent tearing and limb damage by reducing weight of a branch/limb during pruning. Step #1: First cut the underside of the branch, inches out from the trunk, and about one half-way through the branch. Step #2: Second cut is made on top of the branch about 3-4 inches further out from the first cut. As this cut is made, the weight of the branch will cause it to break between the two cuts. Step #3: Cut the remaining stub/branch at the proper branch-bark collar. Limb <1cm diameter, 1 cut method Limb >1cm Diameter, three-cut method II. Drop-Crotch Cut A Drop-Crotch cut or, Reduction-cut shortens a stem or limb back to a lateral branch. The exact location of the final cut will vary from branch to branch. Step #1: Remove limb or stem weight above cut area using the three-cut method. Step #2: Remove the remaining stub or limb with a 45-degree cut, outside of the branch-bark collar. Remove upper weight first with three-cut method Proper 45-degree cut on stem Back to lateral branch junction 6

7 III. Collar-Cuts vs. Flush-Cuts Collar Cuts. (Proper pruning cut.) Reduces wound size from pruning cut. Preserves chemical zone in branch collar for quick sealing of pruning wound. Reduces decay from penetrating deep into the stem. Flush Cuts. (Improper pruning cut.) Increased wound size from pruning cut. Eliminates trees natural and chemical ability to seal wound area from pruning cuts. Allows for decay to spread into tree stem. Promotes decay and disease in trees. Improper Flush-cut Proper Collar-Cut 7

8 IV. Stub & Deadwood Cuts Pruning cuts directed at removing dead wood from a tree, and removing stubs left from prior pruning or broken branches. When removing dead wood there is still potential to damage the stem, branch collar, and other limbs in the tree, so caution most still be taken to minimize potential damage. Remove dead wood and stubs to junction with branch collar. Utilize the three cut method if the branch is >1cm in diameter. Dead wood is rigid, so be cautious of breakage to minimize damage to the tree. Cut made at branch collar Dead wood is rigid, and can break un-expectedly V. Tip Pruning Tip pruning is the selective removal of shoot terminals. Pruning cuts should be made at lateral branches or back to another bud, or growing point. This type of pruning is considered a very light pruning to shape future tree development, or limit growth towards a conflict, such as a road, utility, or other feature. Cut made at lateral bud 1 st year 2 nd year 3 rd year 8

9 b. Principles, Reasons & What To Prune I. Pruning Principles Always know why you are going to prune, have clear objectives. Know when to prune (Best time to prune is November thru February.) Use the proper tools for the job. Make proper pruning cuts. Safety first. II. Reasons to Prune Removal of dead, diseased, damaged, and dying limbs. Repair from storm damage. To control size and form. To minimize or reduce hazards for people and property. To increase sight distance and visibility. To reduce conflicts with roads, fixtures, and utilities. Training trees for proper structure and growth. Maintain tree health. III. What To Prune Dead, diseased, damage and dying limbs. Stubs and broken limbs. Root suckers, water sprouts and epicormic shoots. Rubbing and crossing limbs. Narrow and weak crotches (v-shaped). Limbs in conflict with roads, fixtures, visibility, and utilities. c. Proper Pruning Cuts I. Proper Pruning Cuts Small branches and limbs There are three things to consider when making pruning cuts on small branches and limbs 1. Angle of cut: in order to minimize the surface area of the cut for healing, cuts should be made at a 45 degree angle, this also assist in shedding moisture from the wound. 2. Distance to the next bud: the optimum distance to the next bud is about ½ inch. When cuts are made closer or farther away, the bud is damaged or too long a stub remains, respectively, and healing and new growth will be inhibited. 9

10 3. Inward vs. outward facing buds: this can be used to manipulate the direction of the new growth and the shape of the plant. By pruning back to an inward-facing bud, the new growth will be toward the center of the tree, which will make it denser. Pruning back to an outward-facing bud will produce new growth away from the center of the plant and make it more open. I. Proper Pruning Cuts Large or Heavy Branches Many mistakes are made when people prune large or heavy branches. In many cases, the pruning process often results in damage to the tree. Pruning large or heavy branches (limbs greater than 1cm in diameter) should be a three step process in order to avoid tearing or ripping of the bark while making the cut. When a single cut is used, the weight of the branch or limb may cause the limb and bark to tear several feet down the trunk before the cut is completed. II. The Three-Cut Method --First Cut: This cut is made at the underside or bottom of the limb, approximately inches from the trunk. The cut should be made about halfway into the branch. --Second Cut: This cut is made on the top of the limb, approximately 3-4 further than the first cut. This cut removes most of the branch or limb. --Final Cut: The final cut is made at the branch bark ridge. Since the weight of the limb has been removed, this final cut can be made with precision and without risk of damage to the trunk. 2 nd Cut removes weight of limb 1 st Cut prevents tearing of bark and cambium 3 rd Cut is a branch bark collar Three-Cut Method 10

11 III. Timing a. When to Prune The timing of pruning is very important and depends upon the type of plant and the desired outcome. When trying to decide when to prune, there are a number of factors to consider. Basic Considerations for time of Pruning: 1. Dead, damaged, diseased, and dying wood: --Wood of this type can be pruned anytime of year, and should be removed as it becomes evident. 2. Spring-flowering trees: --These should be pruned after they bloom for the season since the flower is growing on wood that was produced during the previous years growing season. 3. Summer-flowering trees: --These trees should be pruned in late winter (after threat of frost) and/or before new spring growth occurs. Their flowers are borne of wood produced that same year. 4. Trees without flowers: --These should be pruned when they are dormant, typically in mid-late winter or early spring, before new growth had developed. This group includes most deciduous trees, needled evergreens, and many of the broadleaf evergreens. General Pruning Time Table: This table represents ideal pruning times for tree health, but does not reflect the times Lane County vegetation management may occur. J F M A M J J A S O N D (Months) Best time X X X X Worst time X X Light Pruning X X X X X X X X X X b. Tree Health Effects of Pruning at the Wrong Time: Tree health and vigor reduced, increasing susceptibility to disease. Reduced flowering and new-growth of plant material. Increased decay, and pre-mature decline or death of tree. Increased development of suckers and water sprouts. Increased pest susceptibility and development. 11

12 IV. Tree Types There are two main categories of tree types, Hardwoods (deciduous) trees, and Conifers (evergreens) trees. There is a wide variety within each of these groups, and care should be taken to learn and know the specific trees for which pruning activities are planned. a. Conifers (evergreens) Needled evergreens generally don t require much pruning. However, before doing any pruning, you need to be aware of the type of tree you have. There are two broad categories of needled evergreens based on their branching patterns: 1. Whorled branches: These have no buds on needless-shoots so you would only prune to Active, needled shoots. Examples include pine, spruce, fir and Douglas fir. 2. Random branches: There are two types of random-branching needled evergreens. a. Those that have latent buds: These can be pruned back to wood without needles. Examples include yew and arborvitae. b. Those that don t have latent buds: Prune back to wood with green needles. Examples include cedar and juniper. No latent Buds Prune back to green Needles at lateral branch Latent Buds Prune back to wood without needles. 12

13 b. Hardwoods (deciduous) Hardwood trees compared with evergreens may require pruning, ranging from light pruning to heavy pruning based on the objective. However, before doing any pruning, you need to be aware of the tree type you have. a. Spring flowering: Hardwoods that flower in the spring or summer need to be pruned the same, only timing differs to when you should prune. Prune back to lateral living branches, or to lateral buds. When pruning an entire limb, always make your final cut just outside the branch collar, and utilize the three-cut method if the branch is >1cm in diameter. b. Summer flowering: Hardwoods that flower in the spring or summer need to be pruned the same, only timing differs to when should you prune. Prune back to lateral living branches, or to lateral buds. When pruning an entire limb, always make your final cut just outside the branch collar, and utilize the three-cut method if the branch is >1cm in diameter. Pruning cut made at lateral bud, and at 45 degrees Three-cut method for pruning back to stem of tree at the branch-bark collar 13

14 c. Age Class Trees are pruned differently based upon age of the tree. Pruning young trees differs dramatically from that of mature trees, the needs and methods for pruning need to adjust based on the age of the tree. 1. Trees younger than 3 years: The tree needs as many leaves as it can get to produce the energy required for healthy root growth. Pruning at this time should be limited to dead or broken branches, or branches that compete with the central leader of the tree. 2. Trees that are 3-4 years: At this point root growth should be well established. Now is the time to removes suckers, water sprouts, and excessive limbs that reduce competition for light, water and nutrients. A few of the lowest limbs can be removed at this time, but do not remove to many as this can result in reduced trunk diameter and taper. 3. Trees that are 5-8 years: Pruning for future growth at this time is important. At this point the lower limbs are established. The tree should be limbed up to keep the lower limbs clear of pedestrians and vehicles. Branches farther up on the tree should be pruned for even spacing on the trunk wherever possible. Remove limbs that cross others, double leaders, and those that excessively extend beyond the natural crown of the tree. Do not prune or remove more than ¼ of the total crown of the tree in any one growing season. 4. Mature trees: Little pruning should be needed at this time if previous pruning has been done correctly. Pruning at this time should be limited to the removal of dead or hazardous limbs, limbs that restrict sight distance, clearance, public safety, or are in conflict with utilities or traffic fixtures. d. Urban and rural tree conditions. Urban and rural environments have impacts that are distinct to each, and effect trees differently. Tree growth, health and lifespan can be altered based upon where the tree grows. Pruning practices have differing constraints and objectives based upon whether a tree is growing in an urban or rural environment. 14

15 1. Urban Trees Urban trees are challenged by many factors that rural trees never see. Maintenance of urban trees requires special care and consideration before pruning, to not harm the tree. Urban trees require more pruning than rural trees because they are in more frequent conflict with people and property during their lifespan. Root zone restrictions, limited root growth. Shorter life span. Higher maintenance and pruning requirements. Soil compaction and poor soil quality. Inadequate drainage. Limited space for growth. Conflicts with people and roads Limited space for Growth Limited root zone Compacted Soil Street Tree Planting 2. Rural Trees Rural Trees are both planted and natively established, and generally grow in larger more natural conditions than urban trees. Generally rural trees require little management and pruning to maintain proper health and structure. Typically large root zone area. Longer life span. Lower maintenance and pruning requirements. Proper drainage. Limited soil compaction. Adequate space for growth. Fewer conflicts with people and roads. 15

16 V. Tree Health and Structure a. How pruning Affects Tree Growth and Structure Pruning practices aim to benefit tree health and proper structural development. Well intentioned as they are, pruning practices can negatively affect trees if done improperly or at the wrong time. 1. Positive pruning affects on tree health and Structure: Pruning corrects structural defects, such as co-dominant leaders. Pruning promotes healthy tree development by increasing light and air circulation. Pruning promotes proper growth and shape of the tree. Pruning increases energy by reducing suckers, epicormic growth, and water sprouts. Pruning reduces conflicts with people, utilities, roads and structures. Pruning can reduce disease and pest concerns. Pruning limits irregular and improper growth. Pruning can increase the aesthetic value of trees. 2. Negative pruning affects on tree health and structure. Improper pruning can limit growth and reduce energy stores of trees. Improper pruning can decrease plant vigor and health. Improper pruning can open wounds vulnerable to disease and pests. Improper pruning can increase sucker and water sprout development. Improper pruning can promote irregular growth and poor structure. Improper pruning can create hazard trees. Improper pruning can Kill Trees. 16

17 b. Wounds and Sealing Pruning practices and other maintenance activities have the potential to injure trees, creating wounds or injuries to a tree. Trees have a great ability to respond to these injuries and wounds, but we must understand how the tree responds so we can help the process. The first thing to remember is that trees do not Heal, they Seal, off wounds and injuries to prevent decay and rot. 1. Compartmentalization of Decay in Trees (CODIT): CODIT is a concept used to describe the reactions that take place in a tree in response to wounding. When a tree is wounded, it sets up a defensive wall against the invasion of decay fungi, and other pests. The vessels near the wound are plugged with gums, resins and chemicals that resist the spread of decay. The living tissues outside the wounded area then begin to form a callus layer in an attempt to close the wound. A properly made cut results in a doughnut-like ring of callus forming all the way around the wound. Wound closure for small wounds may only take a few months to heal, whereas a larger wound area make take years to close, or may never close at all. 2. Minimizing Wounds and Helping Healing: Make final cut just outside of branch-bark collar. Use three-cut method to limit potential damage, or bark tearing of trunk. Do not paint wounds, trees do much better at healing on their own. Wound treatment should be confined to removal of loose bark or wood. Make cuts as small as feasible to satisfy pruning requirements. Do not make flush cuts when pruning. Do Not leave stubs at pruned area. c. Tree Protection and Common Pruning Injuries Care needs to be taken when working in and/or around trees to minimize the potential for damage. Trees can be damaged in many ways, from soil compaction from machinery, root damage from trenching, trunk damage from being hit, and many other ways. 1. How to Protect Trees from Injury: Keep machinery as far away as possible from the root zone and trunk. Don t store equipment and supplies at the base of a tree. Minimize soil compaction within the drip zone trees. Don t let pruning tools contact the tree stem, causing injury. Mark off areas to be protected with fencing or other barrier. Do a tree assessment, and develop a work plan prior to starting work in a tree. 17

18 2. Common Pruning Injuries: If pruning is done improperly injury can result to the tree. Efforts should be taken to minimize potential impacts during pruning activities, since many of the common injuries can be easily prevented. a. Bark Tearing Occurs when pruning cut is made improperly, and the limb weight causes the connected tissue to tear bark from the stem. Bark Tearing b. Flush Cutting Improper pruning cut, that cuts through or past branch-bark collar producing large wound that increase decay and rot deep into the tree. c. Broken Limbs Can be caused by mechanical damage, dropping pruned material from the tree, pruning equipment, tree workers and other reasons. Flush Cutting d. Mechanical Damage Generally caused my mechanical equipment, such as mowers, brushers, chainsaws and bucket trucks. Opens large wound on tree stem that can cause infection, disease and an opening for pests. Broken Limbs Mechanical Damage 18

19 VI. Sight Distance and Clearance Standards a. Road and Sidewalk Clearance Standards Vegetation that is a hazard to pedestrians or vehicular traffic by reducing visibility, obstructing travel, or posing any other safety risk shall be maintained to reduce the hazard. 1. Sidewalk Clearance Standard Sidewalks and designated areas for pedestrian travel shall be cleared of overhead vegetation to a height of 7-9 feet when feasible and will not cause a reduction in tree health The minimum height for over head vegetation is 7 feet above the sidewalk, and will be considered a trigger for further management activities. 2. Roadway Clearance Standard Streets and roadways for vehicular traffic shall be cleared of all overhead vegetation to a height of feet. The minimum height for over head vegetation is 15 feet above the road surface, and will be considered a trigger for further Management activities. 7-9 Ft. clearance Ft. Clearance 3. Utility Clearance Standards This type of pruning is generally conducted by utility companies to maintain the integrity and safety of utility lines. The general rule is to maintain vegetation at least 10 feet from utility lines. Typical pruning methods to maintain vegetation at least 10 feet from utilities 19

20 b. Proper Sight Distance Standards 1. Intersections No vegetation obscuring sight triangles. Prune tree limbs to minimum of 7-9 ft. over sidewalks when practicable and does not reduce overall tree health. (7 Ft. Minimum.) Prune tree limbs to minimum of ft. over roadways. Maintain safe sight distance for pedestrians and vehicle traffic by pruning or removing trees. 2. Corners No vegetation obscuring inside corners. Prune existing tree limbs to a minimum of ft. height at inside corners. Trees should not be planted within inside. corners to maintain safe sight distances. Maintain safe sight distance for pedestrians. and vehicle traffic by pruning or removing trees. c. Structural Sight Distance Conflicts & General Considerations Provide safe sight distance for vehicles entering roadways from, side roads, driveways, parking lots, and alleys. Promote low-growing vegetation in areas that require adequate sight distance for safety, primarily inside corners, driveways, and intersections. Prune or remove vegetation that obstructs motorist or pedestrian view of traffic signs and signals, street lights and name signs, or other safety fixtures or marking placed in the public right-of-way. Prune for safety and visibility first, tree health and aesthetics second. Inside corners and intersections should have no vegetation exceeding 30 in height, or below 9 feet for sidewalks, and feet for roadways. Prune or remove vegetation that obstructs access to use of any public facility. 20

21 VII. Tree Hazards For a tree to be hazardous it must first have a target, of which, if failure occurred it would damage, such as a house, vehicles, or people. Trees should be monitored to minimize risk of injury to people and property. a. Common Tree Hazards 1. Dead, dying, or damaged limbs Dead, dying, and damaged limbs are a concern because they have either very weak attachments, or are hung-up in the tree waiting for the next wind to fall. Prune all Dead, dying, and damaged limbs from the tree to minimize hazards. 2. Co-dominant leaders This is when you have two stems competing for the dominant stem position. If a co-dominant stem is ½ to ¾ the size of the main stem this is considered co-dominant. As these stems compete they weaken each other, and typically overtime they will split, with either one, or both of the stems failing, producing a large hazard. 3. Bark-Inclusion This is secondary cambium growth, called bark cambium. Barkinclusion refers to this cambium layer as it develops within the crotch of a tree, pushing apart co-dominant stems as it grows. Bark-inclusion causes weak attachment of limbs, by not allowing proper wood development to form at a crucial junction. Bark Inclusion area 4. Decay and Rot Rot and decay in trees reduces structural strength, shows a tree is diseased, or has a wound that has not healed correctly. Some signs can be seen externally, such as conk development, Cankers, and open wounds with exposed wood. 21

22 5. Weak attachments (v-crotch) Weak attachments are created by improper growth of stems and limbs in a very tight V-form. This is bad for a couple of reasons, usually stems in a v-crotch are co-dominant stems, and also there is usually bark-inclusion within the crotch. As the tree ages, the stem diameters increase pushing apart from one another, eventually causing partial or complete failure. b. Signs of Disease Many biotic and abiotic factors influence the health of trees, and many of these factors cause a response, or sign in a tree that something is not right. You first need to know what is normal for a given tree, then determine if some, or any of the trees normal characteristics are noticeably different. Some signs that a tree is stressed or diseased can be very apparent, and some of these signs are listed below. 1. Overall Stunting. Abnormally reduced growth. Abnormally small leaves. Abnormally small flowers or few flowers. 2. Foliar (leaves) Abnormal wilting of the leaves. Scorching of the leaves, or browning of the edges. Blotching, random dead areas throughout the leaves. Chlorotic sings, yellowing or discolor of the leaves. Abnormally twisted or malformed leaves. Uneven leaf fall, one portion of the tree defoliates before the rest of the tree. 3. Stems and Branches. Single branches wilting, or large limb dieback. Stagheading (branches without leaves, with loose bark or no bark) Missing bark, cracks, fissures producing discoloration or dieback. Buds dry, flakey, or dead. The above mentioned list is only partial, but it provides ideas for what to look for when assessing the health of a tree. 22

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