Paving Near Mature Hemlock Trees

(Question)

I have many hemlock trees on my property. I am concerned about paving/landscaping around them due to their shallow roots. Will the compaction of putting in a drive way and interlocking walk way damage them. They have suffered quite a bit due to the ice storm. Thank you!

(Answer)

There are many considerations when planning a driveway/walkway near mature trees, as you have pointed out. Trees have an area called the protected root zone, which is generally the root area under the branches of the tree. Tree roots, which tend to be shallow — over 50% of a tree’s roots are found in the top foot of soil — are necessary for absorption of water and nutrients from the soil, as well as air exchange. Therefore, anything that limits the tree’s ability to carry out these functions, such as paving over soil and/or any resulting soil compaction, has the potential to damage the tree.

If feasible, you may want to consider siting your driveway away from the trees, or designing it with curves it to avoid more of the trees’ roots. Of course, this is often not an option. The University of Minnesota Extension Service advises that driveways can cover up to half the distance from a tree’s protected root zone to its trunk without causing substantial damage, as long as no excavation occurs that may damage the tree roots. Walkways should be located at least three feet away from the tree’s trunk.

There are also alternatives to conventional asphalt driveways that allow air and water to penetrate the soil and reach the tree’s roots. These include permeable pavers, brick, and flagstone, among others. Many of these newer options are also aesthetically appealing and can add to the overall enhancement of your property.

For more information, you can review the full set of recommendations from the University of Minnesota here.

It is also a good idea to consult with a certified arborist who can advise on the needs of your specific trees and location. If you are in Ontario, you can find a certified arborist here.