The following standards regarding trees in the public right of way of Louisville Metro maintained streets are set forth and maintained by Louisville Metro Government’s Division of Community Forestry (Division), the governing body of public trees excluding parks, parkways, and state roads. No tree may be planted, pruned, or removed/replaced in a public space, which includes the green verge* or a tree well in the public right of way, without a permit issued by the Division. Permits for planting new trees will not be allowed if the width of the green verge is less than three (3) feet, the proposed location does not meet the below specified tree spacing standards, and/or Division tree planting standards are not adhered to.
The Division maintains a Master Tree List (refer to Appendix 1A) that clarifies permitted and prohibited tree species. Prohibited tree species listed in the Master Tree List are not allowed to be planted. If a prohibited species is planted, the Division can require the abutting property owner to remove the tree at their expense. The Division has the right to grant permits to plant species not on the list, and the right to waive a standard.
The following tree size types are recognized by the Division and are outlined in the Master Tree List:
*The “green verge” is the pervious surface strip of land in the public right of way. The green verge width is the distance of the green space between the curb and the sidewalk.
The following spacing will be observed based on the lateral distance from the center of the tree trunk.
A. New and Existing Trees: The minimum spacing between two newly planted trees of the same size type is as follows:
Figure 1. Spacing of newly planted trees based off of tree size type A, B, and C (Figure not to scale).
The minimum spacing between existing trees and a new tree will be the distance of one-half of the new tree’s mature spread as listed in Michael Dirr’s “Manual of Woody Landscape Plants”.
B. Street Corners: No tree, whether on public or private property within Louisville Metro, shall be planted closer than twenty (20) feet from any street corner intersection, measured from the point of the nearest intersection's curbs or curb lines.
C. Driveways and Alleys: No tree, whether on public or private property within Louisville Metro, shall be planted closer than ten (10) feet from any driveway or alley in the public right of way intersecting with any Louisville Metro street, measured from the point of the nearest curb or curb line of that driveway or alley.
D. Accessible Parking Zone for Handicap Parking: In cases where current accessible parking zones are established for handicap parking on streets, no trees can be planted in the zone (sign to sign).
E. Planting Distance from Curb or Sidewalk: A newly planted tree will be planted at the halfway point between the curb and sidewalk in green verges with widths of three (3) feet or greater, unless the Division determines that another location is suitable.
F. Overhead Electrical Utility: The following tree size types will be considered when planting in specified distances from overhead electrical utilities:
G. Underground Utility: No trees may be planted closer than 36 lateral inches on either side of any buried or underground water, sewer or natural gas utility line.
H. Other Utilities: No trees may be planted closer to listed utilities other than the defined distances.
I. Traffic Control Signals and Signs: No tree, whether on public or private property within Louisville Metro, shall be planted in such a manner that the tree blocks a traffic control signal or sign. The following are approved distances from sign types for tree plantings:
A permit issued by the Division is required prior to planting a tree in the public right of way. Adherence to the conditions listed on the permit is required. The Division has the right to waive these standards.
Permits for planting new trees will not be granted if the width of the green verge is less than three (3) feet.
Kentucky811 (Before You Dig) has to be contacted and underground utilities marked prior to planting.
All new trees need to be at least 1.5 inch caliper size and branched up to 4.5 feet above ground. Note: Caliper size is measured 6 inches above ground for smaller trees (4 inch caliper size or less).
All approved trees must have a single trunk, unless waived by the Division.
At the time of planting, all trees must be healthy with normal well-developed branching and a fibrous root system. Trees must be free of defects and insect infestations.
Division spacing standards must be adhered.
Scheduled watering should take place at the time of planting, and shall continue for three years. Refer to DCF Tree Watering Regimen (Appendix 1B).
At the time of planting, branching of the tree must be orientated in a manner that discourages obstruction of vehicular and pedestrian pathways.
At the time of planting, trees are required to be mulched and mulched yearly. A 2 inch mulch free radius surrounding the base of the trunk is required. Note: Do not use the volcano mulch method.
The act of planting the tree is in accordance with the American National Standard (ANSI) A300 Planting and Transplanting Practices:
Supporting materials: If the tree is in a container, remove the entire container at the time of planting. If the tree is balled and burlapped, remove the entire wire basket and a minimum of 2/3 of the burlap from top of root ball if not able to remove all.
Planting Depth: The shallowest bottom of the trunk flare should be planted at finished grade, not exceeding ¼ inch above grade (Figure 2). If the bottom of the trunk flare is not visible, excavate and remove excess soil from top of root ball.
Root system: Install the tree in a manner that allows for the root system to be evenly distributed. Prune any girdling or circling roots.
Backfill: Backfill the hole with soil in layers to prevent air pockets. Tap soil down lightly every 6 inches. Do not over compact backfill. Remove any foreign material in the soil. Backfill until finished grade is reached, not exceeding the bottom of the trunk flare.
Root Barriers: A root barrier shall be installed if the root ball is within three (3) feet of any infrastructure or when the green verge width is 6 feet or less. Root barriers are required adjacent to sidewalks. Barrier installation is also required adjacent to the following curb types: vertical curb and gutters, standard roll curbs and depressed roll curbs. Please refer to DCF Root Barrier Installation (Appendix 1C) for root barrier installation instructions and curb types.
Root Barrier Specifications:
Berm: Create a circular soil berm 4 inches high and 8 inches wide (Figure 3). The berm should be located along the perimeter of the hole. If sod is dug in creation of the hole, the Division recommends using sod as base for berm. Flip sod over so grass is facing the ground, and then cover with excess soil.
Water: Slowly add 20 gallons of water. Water should be applied prior to mulching in case the tree shifts.
Mulch: Apply premium hardwood mulch at a depth 4 inches and taper to trunk, with a depth of 1 inch over root ball. Do not apply mulch to the base of trunk --- leave a 2 inch radius of space between trunk and start of mulch. Note: Mulch ring of mature trees should extend to dripline.
Staking: Only stake tree if necessary. Refer to Tree Staking Standards.
Figure 3. Street tree planting standard with berm, root barrier, and staking (Louisville Metro Public Works & Division of Community Forestry Standard Plan No 100)
A permit issued by the Division is required to prune trees in the public right of way or public space. A permit is not required for pruning a branch that is less than a four inch diameter AND causing obstruction of pedestrian traffic, cross-visibility and/or traffic controls.
Equipment: All equipment that is used to perform pruning should be clean of containments to prevent the spread of disease. Climbing spurs are prohibited for pruning.
Limb Removal: Do not cut into branch collar zone (Figure 4, 5). Using the three-cut method (Figure 6), starting with A and ending with C, remove a limb without cutting into the branch collar zone. Do not use wound treatments to cover pruning cuts.
Limb Reduction: Reduce limbs using the limb reduction method (Figure 7), specifically a and b. Cut should be made at a lateral branch or node/bud.
Crown Reduction: Crown reduction is the selective pruning of limbs to decrease the height and/or spread of a tree. No more than 25% of a crown may be removed annually unless permitted by the Division.
Thinning: Thinning is the selective pruning of branches to reduce the density of live branches. No more than 25% of a crown may be removed annually unless permitted by the Division.
Root Pruning: Please contact the Division if root pruning will be conducted.
Tree Clearance Requirements
A permit issued by the Division is required to remove trees in the public right of way or public space. All removals will take place within the timeline specified by the Division. The entirety of a tree must be removed. All excess wood must be removed from site. Stumps must be ground within three months of the removal. Stump grinding is required to a depth of 18 inches below grade.
All trees removed are to be replaced within one year of removal and according to Division standards.
If staking is necessary, use three (3) stakes (Figure 3). Stakes are oriented in a triangle formation around the tree with one stake on the windward side and stake pole on the leeward side. The remaining stake is to be placed at the last vertex point to form a triangle. Stakes are to be driven into the ground at a depth of 6 inches to 1 foot, and outside the root ball. Use tree tie webbing only for securing the tree to the stake; do not use metal material. Tree tie webbing is to be looped loosely around the tree to provide a 1 inch slack for trunk growth and securely tied to the stake. Check the stakes and ties periodically, and remove after one year installation.
Critical Root Zone:
The Critical Root Zone (CRZ) is the area of soil adjacent to the trunk, containing critical roots for stability and tree health. The Critical Root Zone is equal to one (1) foot diameter per one (1) inch of trunk diameter, measured at breast height. Diameter at breast height or DBH is measured at 4.5 feet above grade. For example, a twenty (20) inch DBH tree has a 40 foot diameter CRZ (Figure 8).
Figure 8. Critical Root Zone.
Tree Protection Zone:
The Tree Protection Zone (TPZ) is the area that restricts activities during construction, minimizing or preventing injury to the tree(s). This area includes the CRZ or beyond based off of tree age and tolerance to construction. The TPZ should include fencing, signage, and trunk protection. No clearing, grading or construction shall take place in the TPZ. No structure shall be placed closer than 15 feet from TPZ fencing or boundary line. No vehicle, equipment or retaining wall shall be used or placed closer than 10 feet from TPZ fencing or boundary line. Consult with the Division or International Society of Arboriculture’s Best Management Practices: Managing Trees During Construction, 2nd Edition 2016 for specifics on installation of TPZs.