Proper Pruning Techniques
Why prune street trees?
- There are several reasons street trees are pruned. The most important reason is public safety, including maintaining clearance over sidewalks and roadways.
- In addition, pruning is done to improve trees’ structural stability. This lessens the impact seasonal storms have on structurally unsound branches.
- Long-term maintenance and costs are reduced when pruning is done to young trees. Corrective pruning alleviates many problems early and allows for a more stable and aesthetically pleasing tree.
The City of Dublin adopts two industry standards when pruning. Arborists contracted by the City also follow these standards.
- American National Standards Institute A-300 Pruning Standards
- International Society of Arboriculture – Best Management Practices for Tree Pruning
Who is responsible for pruning City-owned street trees?
The City of Dublin’s Forestry staff maintains and prunes all City-owned trees. We ask residents not to prune the trees in front of their home, but contact the City Forester for a pruning request at 410-4701 or by e-mail at firstname.lastname@example.org.
Which trees are owned by the City?
- City-owned trees are those trees growing within the public right-of-way. Most trees are in the area of land between the street and the sidewalk. If there is no sidewalk, the City-owned trees may be planted approximately 4 feet off of the curb.
How often are the street trees pruned?
- Street trees are pruned on a three- to four-year cycle. Certain species, such as honeylocust and elm, may be pruned every one to two years because of their vigorous growth rates. The goal is to prune every street tree in the City of Dublin at least once every four years.
How much is removed at any one pruning?
- Industry states that the maximum that should be removed during a pruning cycle is 25 percent to 30 percent of the foliage. This amount is not removed for every tree pruned
Should wound dressings be used?
- It is not recommended that any wound dressings be used. In the past the benefits of “pruning paints” were widely touted. Research in the last couple of decades has shown that paints offer little, if any, positive contribution. In several studies, paints have been shown to be harmful because they don’t allow the wounded wood to dry. Most fungi that attack trees need wet wood to infest. After a period of time the paints crack, allowing access to the wet wood beneath. In some species, the presence of the paint slows wound closure.
Can my tree be topped?
The arboriculture industry does not promote tree topping as a maintenance tool. The City of Dublin’s street tree ordinance prohibits this practice. This is in compliance with the International Society of Arboriculture and the ANSI A 300 Standards.
- Mulch should be no more than two to three inches thick. This includes previous year’s mulch.
- Mulch should not be mounded up around the trunk of the tree. It should be tapered away from the trunk.
- Additional top soil or edging should not be added to the top of the mulch. For the health of tree it is important to be able to see the root flare.
- Newly installed trees generally require one inch of water every seven to 10 days for the first year after installation.
- If there is an irrigation system present, be sure to monitor rainfall levels so you do not overwater. Overwatering can lead to lack of oxygen in the soil, causing stress and possible death for the tree.
- Exercise caution when applying chemical treatments to your lawn and landscape plants. Some trees are more sensitive to herbicides than others. Remember, most lawn weed killers are designed for broad-leaved plants — of which trees are a member. Be careful how you apply these chemicals around tree trunks and lower branches to avoid overspray.
- Follow manufacturer’s directions. More is not better.
- Do not use herbicides to control root sprouts emerging around the tree trunk. These are connected to the tree’s root system. These should be cut back with hand pruners.
Why are trees being removed when sidewalks are being replaced?
- The sidewalk replacement program is an initiative to ensure public safety and is in compliance with the recent revisions to the A.D.A. (Americans with Disabilities Act). Under this program any two adjacent sidewalk panels with a one inch or greater degree of vertical separation need to be replaced. The area under these raised panels must be excavated to correct the cause of the misalignment.
- The two main issues causing these problems are soil settlement and tree roots pushing up the panels. The tree roots are cut and removed so the replacement panel can be installed according to code. Older areas of the City have a greater incidence of sidewalk issues. These areas have been addressed first. All City sidewalks will be inspected as the program progresses.