Retaining Walls & Trees: A Delicate Friendship

You have a yard with beautiful mature trees. You also have a yard in need of a retaining wall. These two things often make poor bedfellows. In many cases the trees are simply ripped out to make way for other landscaping – but your story doesn't have to end this way!

Generally speaking any grade change (slope) and soil compaction around a tree will affect the health of its roots especially for those that like to grow their roots closer to the surface, but with some careful planning, your trees and walls can become fast friends.

Before You Begin:

Have an arborist or a tree expert evaluate whether preserving the tree(s) around the construction area is worth your time. They can tell you which trees deserve preservation and which ones you can do without. They can also give you tips for detecting signs of stress and how to deal with it.

The Protection Zone:

The area around the tree going out to the drip line needs to be preserved and protected if the tree is to survive construction.  The drip line is the perimeter of the tree canopy.

Under all circumstances you want to avoid any action that will cause soil compaction in the protected zone. Here are some things to avoid in the protected area:

• Heavy traffic from equipment and vehicles.
• Do not use that area for storing heavy equipment.
• Piling construction materials such as rock, sand and chemicals. 

Designing Your Wall:

Design your walls with curves and serpentines to go around the trees. Terraced walls can be used to avoid grade changes within the drip line area.

Your concerns and intent to preserve your trees should be well communicated with all parties involved in the construction of your project. While working with your local tree expert, involve your construction crew to make sure all guidelines are reachable and will be respected during construction.

Maintaining balance can be difficult but if you plan ahead and seek professional advice, you should be able to complete your project without harming your trees.