Driveway dilemma

Image: iStockphoto

We have an 80-foot Douglas fir growing along the side of our long narrow driveway. The tree is beautiful and appears to be very healthy. However, since we acquired this property some six years ago, its roots have broken the asphalt driveway in so many places that the driveway now needs to be repaved. Before we can do this, it would be necessary to cut the big roots of the tree that has encroached on the driveway. Do you think we can do this without killing the tree? We would very much like to keep the tree, but our driveway has become an obstacle path for anyone coming to see us.

Douglas Justice, Plant expert

While it is difficult to make an accurate assessment without actually observing the tree first-hand, it’s probably a safe bet that cutting off the roots will cause a number of problems, not least that the tree’s stability in the wind will be compromised.

Pseudotsuga menziesii (Douglas fir) typically produces roots near the soil surface because its roots require oxygen. Under pavement, soil will generally be compacted and dry, so the roots grow at the surface. The ideal solution is to remove the pavement, rehabilitate the soil and create a bridge of some kind over the area in which roots are present or are likely to colonize. Barring that, removal of the pavement and replacement with a deep layer of coarse gravel will allow water and air to penetrate and will prevent compaction.

It is important to keep such a tree healthy, as this species is prone to branch breakage, and stress will increase the likelihood of this occurring.