URBANA, Ill. — While essential for development, construction projects often damage trees and their intricate root systems. Even the beautiful trees that are sitting on a site and desired to be kept following construction can become damaged and later experience decline. Property owners then face costs for removal and replacement. Protecting trees and their roots is an integral part of construction projects like remodeling, sidewalk and driveway installation, landscaping, or utility work.

Construction-related tree injury occurs through physical damage like equipment collisions, soil compaction, or cutting and severing roots. Injury also occurs through environmental changes like sudden exposure to wind and sun through pruning, fluctuations in soil moisture, or soil nutrient availability.

Identifying tree stress is essential for early intervention. However, because trees may exhibit symptoms months or years after damage occurs, several years may pass before symptoms arise from soil compaction or root suffocation. Because of this delay, it can be difficult to recognize the relationship between construction damage and its symptoms. 

Injuries might result in leaf wilt, early fall color, dieback, stunted growth, and premature leaf or needle drop. Evidence of physical injury can be visible wounds on the trunk or exposed roots. 

To protect trees, mark the placement of proposed structures, parking areas, sidewalks, and utilities. This will aid in establishing a tree protection zone for trees that will remain. It is important to note that the roots extend far beyond the tree’s canopy, and protecting the largest root zone possible will greatly benefit a tree’s health. Prioritizing requires careful consideration of each tree’s species, health, and structural integrity. Give precedence to healthy, mature trees that benefit the ecosystem as a source of food or shelter for wildlife.

Certified arborists can assist in preservation decisions by providing insight into tree health. These professionals adhere to accepted standards regarding tree management, protection during construction, and many other industry requirements.

Steps to minimize construction damage

• Communicate with contractors about protecting mature trees. Install construction fencing around tree root zones to create a physical barrier and visual reminder for workers.
• Restrict heavy machinery and construction traffic from entering tree protection zones to mitigate soil compaction and root damage. Tree roots are concentrated in the top 6” to 18” of soil.
• Use mulch and temporary ground cover to prevent soil compaction during construction.
• Remove undesirable trees over winter when leaves are absent to lessen the degree of sunburn on nearby trees.
• Consider tunneling utilities beneath tree roots instead of trenching to minimize root disturbance and preserve root structure. Tunnel at least 2’ away from the trunk and at least 2’ underground.
• Avoid significant grade changes near trees to prevent root exposure and destabilization. Conversely, piling more soil around trees can smother roots.

Steps to encourage recovery and long-term health

• Aerate compacted soil around trees to improve root oxygenation and nutrient uptake.
• Provide supplemental irrigation to trees, especially during dry periods, to aid in root establishment.
• Apply a 2” to 4” layer of mulch around the base of trees to prevent soil compaction, conserve soil moisture, suppress weeds, and protect the trunk from mowers and trimmers. Keep mulch several inches away from the trunk to avoid rot and other problems. 
• Regularly inspect trees for signs of stress or damage and address issues promptly.

Protecting trees and, specifically, roots during construction requires a proactive and multidimensional approach. By understanding the types of damage, recognizing symptoms of distress, making informed preservation decisions, and using preventive measures and proper care practices, communities can safeguard more trees in our urban landscapes.

For more on protecting and caring for trees, connect with a local University of Illinois Extension office at go.illinois.edu/ExtensionOffice.

Sarah Vogel is an Illinois Extension horticulture educator for DeWitt, Macon, and Piatt counties. Gardeners Corner is a quarterly newsletter from gardening experts around the state. Each issue highlights best practices that will make your houseplants, landscape, or garden shine in any season. Join the Gardener’s Corner email list at go.illinois.edu/GCsubscribe for direct access to timely tips.

PHOTO CAPTION: Tree buried by grade change during construction work. Photo by Big Stock.