Q: I have a locust tree in my front yard that has such severe surface roots that it is difficult to mow the grass. I am afraid that the tree will die if I try to remove the roots. I thought about adding more soil and reseeding, but I understand that the roots will just grow to the surface again. I have a maple tree in the back yard with the same problem. Is there a way to manage this problem without removing the trees?
A: You are wise to resist the temptation to cut those roots. They are important to the health and vitality of a tree. Surface roots are actually lateral roots that often grow near the surface. They function in the transport of water and nutrients and are important to anchor the tree to the ground. Sinker roots -- roots that grow straight down into the ground -- grow off of lateral roots.
Although certain species of trees seem to cause more of a problem with surface roots than others, most large, older trees will produce some surface roots. It is a common misconception that tree roots grow very deep in the soil. Most tree roots are found in the top 6 to 18 inches of soil. As the tree grows in height and diameter, so do the roots, which eventually brings them to the surface.
Norway maple (Acer platanoides)
Red maple (Acer rubrum)
Silver maple (Acer saccharinum)
Tree-of-heaven (Ailanthus altissima)
Alder (Alnus spp.)
River birch (Betula nigra)
Hackberry (Celtis spp.)
American beech (Fagus grandifolia)
Thornless honeylocust (Gleditsia triacanthos var. inermis)
European larch (Larix decidua)
Sweetgum (Liquidambar styraciflua)
Dawn redwood (Metasequoia glyptostroboides)
Mulberry (Morus spp.)
Colorado spruce (Picea pungens)
Sycamore or London plane tree (Platanus spp.)
Poplar (Populus spp.)
Pin oak (Quercus palustris)
Black locust (Robinia pseudoacacia)
Willow (Salix spp.)
Elm (Ulmus spp.)
Bald cypress (Taxodium distichum)
Linden (Tilia spp.)
Many of these are trees that tend to tolerate adverse growing conditions. Their propensity for producing surface roots aids in their survival in such situations.
Environmental factors play an important role in the growth of surface roots. They are common when a tree is grown in hard, compacted clay soil or in areas where the soil is saturated with water frequently. Roots tend to grow where they find the most favorable conditions: adequate water, air and nutrients. In poor growing conditions, the most favorable place is often close to the soil surface. Also, erosion can expose a tree's lateral roots.
Cutting surface roots can injure and weaken a tree and make it more susceptible to insect and disease problems that can eventually kill it. Cutting surface roots also creates a hazardous situation because they serve to support a tree. Without them, it could fall in high winds or during heavy rains.
Even if you cover them with soil and reseed the area, those roots will just grow back up to the soil surface as they continue to grow in diameter. It is not a good practice to place additional soil over the root system of any tree because roots need oxygen. If they are buried too deeply, they literally suffocate, and the tree will decline and die over time.
Finally, running over those surface roots with a lawn mower is not a good idea. The mower causes wounds, which can serve as an entrance into the tree for insect problems and/or disease-causing organisms. Besides, it's hard on the lawn mower and you!
Goldenstar (Chrysogonum virginianum)
Creeping lily-turf (Liriope spicata)
Russian arborvitae (Microbiota decussata)
Allegheny spurge (Pachysandra procumbens)
Japanese spurge (Pachysandra terminalis)
Creeping myrtle (Vinca minor)
Barren strawberry (Waldsteinia ternata)