Unruly Roots

There are some tree questions arborists seem to get more than others, questions that anyone who has moved into an older (or newer) home with existing mature trees is likely to have. Often because trees are planted as saplings, or are simply smaller during home construction, their full-growth size is hard to imagine 20 years down the road. A question, in particular, I hear often from community planners, HOA’s, and homeowners alike is:

“What can I do about the roots that are raising up my driveway/sidewalk..?” 

It doesn’t help that there’s a lot of bad advice out there from seemingly professional sites. For instance, “The tree is unstable and or overgrown…” or one of my favorites; “The roots have grown out of control!!!…” 

In actuality, your tree is rarely the culprit. Driveway companies often have one method of construction whether it’s asphalt, concrete, or any other surface. The problem is that what works on one type of soil may not on another. Some soils swell and shrink more than others, and as a result of poor design and soil conditions, sloppy pavement construction heaves and settles and roots will often follow the gaps created. If you add in heavy erosion such as we’ve seen in the past few years with record rainfall, it’ll take an impressive product to compete with that level of change.

So how can we know about soil variations? The USDA Natural Resources Conservation Service offers soil survey maps that illustrate these variances. So, if you’re replacing a damaged driveway or sidewalk, ask the contractor what their method will be to decrease the likelihood of future damage. Is the design specific to the soil composition in your area? Alas, root cutting or tree removal may in fact be necessary, but I think more often it isn’t, and if you’re receiving advice to remove an otherwise healthy tree, get another opinion — or three!