Sunday, February 11, 2007

Do tree roots keep coming up for air?

Do tree roots keep coming up for air?

Tree roots need oxygen as well as moisture and nutrients. As the roots near the surface continue to grow and increase in diameter, they often end up breaking the surface of the lawn. These roots give the tree character and uniqueness, but the lawn mower is usually not very happy with this situation. The lawn mower (machine) will complain because its blades will be dulled or bent if they twirl into these surface roots. The lawn mower (person) is likely to be unhappy because the lawn mower (machine) is unhappy and also because to some lawn mowers the roots detract form the appearance of the lawn.

What can be done about these roots?

Some people cover the roots with soil, then plant seed or sod to smooth out the lawn under the tree. As long as the depth of soil is minimal, this can be a temporary solution. If too much soil is placed over the roots, the flow of oxygen to the roots will be impaired and the health of the tree can be affected. The problem with adding soil is that eventually, the roots will rise again and the lawn mowers may once more be affected by the exposed tree roots.

What happens in natural situations? In the forest, the roots may be exposed, but since there are few lawns in the woods, no one seems to mind. Usually there is leaf and twigs littering the ground. These tend be less likely to pack down and to thus restrict the flow of oxygen to the roots. Thus the roots have less need to rise up above the surface. In suburbia, the soil usually has less organic matter and is more likely to be hard, impermeable and just down right tough on tree roots.

Under trees whether the roots are exposed or not, consider emulating the forest conditions by applying a layer of mulch 2-4 inches deep. This permits better oxygen exchange to the roots, reduces weeds, and also reduces water loss from the soil. Certain perennial ground covers or plant may tolerate the shady conditions under a tree better than a lawn. Hostas, perwinkle, lily of the valley, pachysandra are just a few. Trying to grow a decent lawn under a tree is not always easy, so looking at alternatives may be one way to keep your tree and lawn mower content.