Have your sights set on adding a room, a new patio or a larger driveway? Make sure plans include protecting your trees. Any construction project, large or small, can cause serious, long-term damage to the trees in your yard.
“You may be renovating your house or garden to add value to your home,” said Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle. “Mature trees also increase the value of your property. If your construction damages or kills your trees, it can cost you in the long run.”
Much of the damage during construction occurs to the roots, the tree’s critical underground structures. “The roots are out of sight and out of mind, so it’s easy to forget to protect them,” Yiesla said. “If a tree’s roots are severely damaged, or if the soil is disturbed so that the roots can no longer survive there, it can kill the tree.”
The damage is often not immediately apparent, and it could take years to slowly wipe out the life of the tree. At the point when a tree is dying, a homeowner may not think to connect the problem to a room addition or a new patio installed several years earlier.
The trees to worry about aren’t just those that are directly in the path of the project. “Tree roots extend widely, two to three times the height of the tree,” he said. “Most of them are only a foot or so below the ground surface.” Any tree within 30 to 40 feet of your project may have its roots severely damaged by construction. On a city lot, that means any trees in the lot or on the driveway must be protected.
The time to plan for tree protection is before you hire the contractor. “Include it in the specifications,” Yiesla said. “Don’t hire a company that won’t take care of your trees.”
Some types of damage are obvious: a truck or front-end loader could accidentally hit the trunk or low branches, or a bulldozer could cut roots. If the anchoring roots on one side of a tree are cut to install a footing or sidewalk, the tree can become dangerously unstable.
Some of the worst damage occurs when soil is compacted with heavy weights. In compacted soils, where all spaces for air and water have been closed, tree roots cannot survive.
A single heavy truck passing just once over the soil surrounding the roots of a tree can cause irreparable damage. Heavy piles of building materials, such as bricks and gravel, or even wheelbarrow and foot traffic, can also compact the soil.
Tree roots can also suffocate if the soil grade is changed so that they are buried too deeply. “The roots naturally grow just below the soil surface,” Yiesla said. Landscape architects and contractors must create plans that avoid grade changes that would damage trees.
Before construction begins, work with the contractor to plan for tree protection. It’s worth investing in a consultation with a certified arborist to make sure you’re doing everything you can.
Mark root protection zones around each tree. If possible, include multiple trees in a larger buffer area. Surround areas with strong, conspicuous fencing to ensure that the protected area is not breached and mulch the soil within it. Water trees deeply before construction begins.
Limit the area available for construction equipment, material storage, and foot traffic as much as possible. All contractor crews must adhere to a designated route that minimizes damage to soil and trees.
You can learn more about preventing building damage at mortonarb.org/protect-construction. “Make sure your new amenities don’t destroy the beauty, shade, and property value you get from your trees,” Yiesla said.
For advice on trees and plants, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-cliniceither firstname.lastname@example.org). Beth Botts is a staff writer for the Arboretum.