So you want to install a new concrete driveway because you are tired of looking at your “bumpy” asphalt. You have noticed that over time, your asphalt keeps breaking up and your tree keeps growing bigger roots that are cracking the driveway. You think, “I will dig up the asphalt, cut the tree roots to get them out of the way, and then install a concrete driveway that will be more resistant to any future root problems.” Before you go this route, read on.
Tree roots, which are mostly under the soil, actually comprise a large portion of a tree's mass and are essential to tree health and safety. The roots act like anchors for the trees providing it stability. The roots will absorb water and nutrients which provides the essential elements for the tree to grow and survive. The roots also act as a storage place for the tree’s food supply.
Cutting a root is like cutting a main artery in your own body and by doing this you risk killing or at least doing serious harm to the tree. By removing that large root that lifts up your asphalt, you are eliminating over 25 percent of the tree's total root system. This damage can be seen immediately with effects such as leaves dropping off the limb, the limbs dying, or the tree begins to lean. Oftentimes, the damage may not be seen for 3 or more years, but can result in premature death of the tree as a whole.
This is not to say you cannot cut any root that may be in your way. It means that you have to understand the tree’s root system, how it grows, and how to properly cut the bothersome root. By knowing this, you can significantly reduce the harm to the tree, and possibly to you and your property.
If, after your research, you feel that you can cut the root safely, then first, make your cut as far from the trunk as possible. To see how close to the tree base you can cut the root, measure the diameter of the trunk at a point 4.5 foot above the ground. Take this number and multiply it by 6. That result will tell you how far from the tree base that you will need to make the cut.
Be aware that by cutting this one root, that the tree will react by producing a large number of smaller roots, which may cause future issues.
The best way to make sure you and your tree are safe, is to call your local arborist or your forestry department.