Landscaping and construction projects can easily break tree branches, injure tree trunks, and damage roots, leaving trees stressed, susceptible to insect and disease problems, or no longer stable after the work has been completed.
Preventing these problems is always better than trying to fix them after the fact! So, if you have a construction or landscaping project planned, take some time to plan for the safety of your valuable trees before construction starts. This will help ensure your trees, and the surrounding landscape, continue to flourish.
Conduct a Thorough Evaluation Before Work Begins
The first thing you can do is document your site as it is by taking photographs. Document your trees’ condition and appearance before construction starts so, if any damage occurs, you have a way to measure it. Identify or number each tree and note its location on a drawing of your property (a hand-drawn sketch is fine). Then photograph the following:
- its surroundings,
- its root flare at ground level,
- its dripline, and
- its trunk and branch structure.
Be sure to also photograph any existing damage or disease.
Consider a Tree Valuation
If you have valuable or heritage trees, or just vigorous, mature trees, a tree valuation inspection before construction may be a good idea. This is a process by which the monetary value of a tree is calculated, and its replacement cost set. If an accident occurs and you lose a tree, you’ll have a system for remediation or replacement.
The needs of new landscaping and construction and the renovation of built-up sites are at odds with the needs of existing trees right from the start. Making a plan for your trees before, during, and after site construction is the best way to ensure their safety and health.
Common Types of Tree Damage From Construction
Like icebergs, there’s a lot more to trees than what you see above ground. A tree’s extensive underground root system is how it gets water, oxygen, and vital nutrients from the soil. Roots are also the anchoring system that keeps a tree securely rooted and able to withstand high winds and storms.
All parts of a tree, both above and below ground, are at risk for damage from construction. Each phase of your construction project should have a plan that takes the protection of your trees into account.
Damage To Tree Roots
A tree’s roots are its lifeline and they are particularly susceptible to damage in project sites. A tree’s feeder roots take up food and water for the whole tree, and a tree’s anchoring roots keep it stable and safe in the ground.
During construction, it’s important to protect those roots. Since a tree’s root system extends far beyond its trunk, this can be a large area to monitor and protect.
The construction activities that most commonly damage tree roots include:
- Trenching for utility or irrigation lines, which cuts all roots that cross the path of the trench.
- Re-grading existing soil for drainage or new paving usually exposes root systems or severs roots, both which can be deadly to a tree
- Excavating soil around tree roots for new footings, foundations, or for a garden pond
- Soil tilling around tree roots to create new planting beds or for installing new sod
What To Do
Before construction, prepare a plan drawing that shows both existing trees and any proposed excavation, trenching, and re-grading. This can be used to decide where to install protection methods and to ensure you’re protecting a large enough area around each tree.
Damage To Tree Branches And Trunks
Construction sites are generally busy places, which increases the chance that a truck, excavator, cherry picker, or other heavy equipment may collide with an existing tree. In a match-up between tree and machinery, the tree always loses, resulting in damage to the tree’s trunk or branches either at ground level or in a tree’s crown.
Tears and gouges to a tree’s bark are serious wounds as these expose the vulnerable interior of a tree to pests and diseases. These wounds require a lot of internal sealing off of the damaged area by the tree. Broken or ripped off tree branches can also cause serious damage and will require corrective pruning.
What To Do
Before construction, prune back or remove any low-hanging or wide-spreading branches that may interfere with construction. It’s better to cleanly remove a branch before damage occurs than to repair damage to a broken branch.
Have tree protection installed around the trunk of all trees that are in or around a construction area. This visible tree protection lets crews know to stay away.
Because it’s invisible, soil compaction is often overlooked as a factor in tree damage, but it should definitely be addressed. Heavy vehicles and staging areas for materials can quickly compact soil, with wet or saturated soils compounding the problem. Compaction compresses soil particles together and prevents roots from growing, reduces oxygen levels in soil, and prevents water from penetrating the soil’s surface. For an established tree, these changes can be fatal.
What To Do
Before construction, lay out vehicular routes and staging areas, and make sure that their perimeters are flagged. Then add six inches layer of organic mulch or straw over these routes and top the mulch with strong plywood sheets or steel road plates. The cushioning layer of mulch will protect the soil surface and the rigid coverings will spread the weight of vehicles and materials over a larger area of soil, lessening the effects of compaction. Any additional protection, such as fencing and enclosures around trees should be installed at this time.
Changes To Soil Levels
The top one foot of soil contains the majority of a tree’s roots and most of the water, air, and nutrients that your tree needs. Adding soil over the existing soil surface smothers roots by depriving them of oxygen, and changes how water moves through soil. Scraping off soil removes and exposes those same tree roots, and exposure to air will kill them.
What To Do
If your construction project involves re-grading your site for footings, foundations, driveways, or paving, be sure your existing trees are taken into account. Bring up any concerns about existing trees with your designer or contractor when your construction project is being designed. This will help ensure your designer includes tree protection as part of the site design’s constraints.
Before construction, verify that your plans accommodate tree roots as much as possible. Even slight changes to the existing grade, either by adding soil or removing it, can damage your trees.
If soil excavation is required, make sure any newly exposed soil is immediately covered by a tarp and kept moist.
Changes To Sun And Shade Levels
You may not be able to prevent the construction or demolition of structures that determine the amount of sunlight that reaches your trees. In this case, the best thing you can do is help your trees to remain healthy; this will give them a better chance of successfully adjusting to their changed conditions.
What To Do
Before construction begins, ensure there’s plenty of tree protection installed around the affected trees. In addition to physical barriers, adding a layer of wood mulch over the trees’ drip line will help keep the soil temperature constant and reduce water evaporation. In hot weather, maintain an irrigation system for the trees to prevent heat and water stress. Do not prune the trees unless absolutely required for safety, and avoid high-nitrogen fertilizer that will stimulate leaf growth when trees are stressed.
What To Do During The Construction Project
During construction, it’s important to regularly inspect the site and make sure all your tree protection has been implemented and is being maintained and respected. All subcontractors should be familiar with your tree protection methods, and the general contractor should organize all project tasks to avoid damage to existing trees.
Here’s what to look for and do during landscaping and construction projects:
- Check that tree protection is in place – Ensure all tree protection enclosures are stable and protect as large an area of a tree’s root system as possible. A tree’s drip line is a typical perimeter, but in this case more is better. If stakes, fencing, flags, or signs have been removed, relocated, or damaged, ask that they be repaired
- Remove debris – Debris should be regularly hauled away, and not left on site where it will take up valuable space. No debris should be piled around existing trees or “temporarily” stored.
- Minimize on-site storage – Material storage and staging areas should be cleared after each phase or subcontractor’s work is done, to lessen soil compaction and to keep space clear. Inspect any materials that might spill, dissolve, or leach into soil and damage trees to make sure they’re properly stored.
- Keep an eye on your trees – Verify that any work near existing trees is being performed correctly, that tree-friendly tools such as air spades are used whenever possible, and that any trenching or excavation work that requires inspection and approval has its soil volume replaced as soon as the work is approved.
- Communicate clearly – Reiterate to any uninformed crew members the importance of protecting trees.
- Document any tree damage – Document any damage to trees as you find it, and make sure your contractor is aware. Any corrective tree work should be done as soon as possible, and any damaged tree should be fully evaluated.
What to Do When the Project is Completed
When all construction is finished, walk through the site and document any changes or damage caused by construction. Comparing finished conditions to the “before” photographs will verify what’s new and what was existing.
Here are some specific things to check:
- Check that all debris and construction materials have been removed, and that debris such as concrete has not been left in the soil where it can change soil pH.
- Check all new irrigation or water pipes to make sure they’re working as designed, and that there are no leaks that can saturate the soil around trees.
- Check around the trunk flare at the base of your trees to make sure that no “extra” soil from excavation has been spread over the existing soil. If so, ask to have it immediately removed to prevent root damage.
What to Follow Up on After a Construction Project
You should monitor the health and vigor of your trees after construction is complete to ensure their seasonal growth patterns are continuing as usual and that they don’t exhibit symptoms of stress. If you notice any signs of decline, call your tree care professional right away to evaluate the tree.
Your trees will also benefit from some additional care in the year after construction:
- Make sure existing trees have the same level of irrigation as they did pre-construction
- Keep mulch replenished around the base of your trees
- Apply compost to your soil for slow-release, long-term nutrients for your trees
And monitor any tree damage so that if problems develop you can treat them right away. These include:
- areas where tree bark was gouged or removed,
- any pruning cuts that were made accommodate construction, and
- the overall appearance of trees where their roots may have been damaged.
Some trees enter a period of slow decline after being damaged and don’t regain their previous vigor. However, with proper care, many trees will slowly recover and continue to grow for years to come.
Ideally, both you and your trees will survive the disruption that construction projects cause and come out of the experience with a healthy, structurally sound, and beautiful landscape.
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