Land Connections  

This mailer has been provided as an avenue to disperse information pertinent to public agencies and the landscape architecture profession in hopes of fostering greater understanding and collaboration. Topics address issues that affect the built environment within which we live.


Protecting Mature Trees From Construction Damage

"For in the true nature of things, if we rightly consider, every green tree is far more glorious than if it were made of gold and silver." Martin Luther.

As was discussed in the last issue of LAND Connections, mature trees provide an array of benefits to society and the urban landscape. As society begins to realize the value of mature trees in the landscape, the preservation of these trees becomes ever more important. Preservation of mature trees in the midst of proposed urban improvements is the focus of this issue and can be accomplished when approached properly. Not all mature trees however, can or should be preserved. Before a decision is made to preserve or remove an existing tree, a certified arborist should be consulted to determine the most appropriate course of action. There are three stages during which measures should be taken to protect an existing tree from construction activities: Pre-Construction, Construction, and Post-Construction.

Pre-Construction Efforts
This stage is critical to address before construction workers, machinery and materials arrive on site. These measures will help insure that all construction efforts are focused on the same goal of project completion with tree preservation.

  • Measure 1: An arborist should make determinations and calculations regarding acceptable critical root zone and protection zone limits.
  • Measure 2: During the design process, when feasible, do not encroach within the driplines of trees to accommodate the installation of utilities, infrastructure or building structures.
  • Measure 3: A tree protection plan should be in place showing protected trees and the extent of protected areas (driplines of trees). This should be approved and implemented prior to occupancy of the site.
  • Measure 4: Install construction fencing around each tree or group of trees to be protected. Attach a warning sign to the fencing clearly stating activities forbidden within tree protection zones.
  • Measure 5: Install wood snow fencing around the trunk of each tree to protect from inadvertent mechanical damage.
  • Measure 6: When the trees are located in an area that will be needed for access to the site or that may receive vehicular traffic, install mulch and plywood panels or rigid panels to entire protection area.

Construction Efforts
During this stage of the process, it is imperative that a certified arborist be on site during construction operations within driplines of protected trees. The arborist should be on-site to direct or halt operations if tree health is compromised. The following measures should be taken:

  • Measure 1: Excavation of earth within the protected zone should be done with flat edge tools. These tools are used to loosen the soil, not to remove it. Removal of the soil should be accomplished with the use of an industrial strength vacuum. Water may also be used to loosen and remove soil.
  • Measure 2: Roots damage by excavation activities should be severed cleanly with sharp tools. Large roots should not be cut.
  • Measure 3: Do not allow exposed roots to dry out. Cover the roots with wet burlap or fabric if the trench will not be backfilled immediately.
  • Measure 4: If utilities must be routed within 5' of a tree, install utilities by boring or tunneling methods thus minimizing damage to tree roots. Avoid tunneling directly under the tree as some trees have tap roots.
  • Measure 5: Do not allow the soil grade within the tree protection zone to be altered or compacted in any fashion.
  • Measure 6: IMPORTANT! Keep construction warning fencing intact and in place at all times. A fallen fence becomes an unintended invitation for construction activities to occur within the protection zone.

Post-Construction Efforts
The ultimate goal is to complete the construction phase with a healthy, virtually unaffected tree. Often a tree will appear perfectly healthy following construction but will unexpectedly show signs of stress and decline in health. Sometimes the effects of construction can take years to fully manifest themselves. This being the case, it is important to plan for continued and routine observation of trees located within recent construction zones. The following measures should be taken:

  • Measure 1: A certified arborist should be retained by the owner.
  • Measure 2: Trees should be observed routinely for indications of stress and deteriorating health.
  • Measure 3: If necessary, the tree may need additional care in the form of irrigation, fertilizer, soil aeration or inoculants. This determination will need to be made by a certified arborist, as the health of some trees (California native oaks in particular) may not benefit from additional irrigation or fertilizers.

These are general suggestions that will help preserve trees from construction activities. Each site and tree, however, will need its own specific preservation plan. Variations in sites, tree species, weather conditions, soil conditions, construction impact levels, and future site uses, all must be assessed when preparing tree preservation recommendations. Be sure to involve an appropriate professional, early in the design process, to improve the odds of preserving existing healthy trees in the landscape.

O'Dell Engineering

The next time you need a Landscape Architect on your project, consider O'Dell Engineering's Landscape Architecture Department.

Services include:

  • Park and Playground Design
  • Recreational Facility Design
  • Site Planning
  • Streetscape Design
  • Urban Design
  • Commercial Design
  • 3-D Visualizations
  • Graphic Design
  • Arborist Consulting


Pre- Construction






  • Trees & the Urban Environment Part I
  • Universal / Inclusive Design - Part I-Playgrounds
  • Universal / Inclusive Design - Part II-Walks & Trails
  • State Model Water Efficient Landscape Ordinance
Author: Chad Kennedy, Landscape Architect

This informational article provided by O'Dell Engineering - 1165 Scenic Drive, Suite A, Modesto CA 95350