Silver Maple Tree Roots Are Killing My Lawn

Root Structures

• According to Kelsey Sparks and Mary Meyer of the University of Minnesota's extension, it is a common misconception that tree roots grow primarily down into the soil. On the contrary, 90 percent of most tree species' roots are in the top 3 feet of soil and 50 to 75 percent of their feeder roots are in the top foot. The roots sent down into the soil are for stability and moisture collection, but most of the roots used to collect nutrients and water are near the surface. Silver maples, poplars and willows are known for their extensive surface root systems.

Surface Roots Kill Grass

• Roots surface for a variety of reasons, but trees with shallow root structures -- such as the silver maple -- are more likely to develop exposed surface roots. As the tree grows, its trunk increases in girth; similarly, so do its roots. As the roots thicken, they are more likely to protrude above ground. Soil erosion might also uncover shallow roots. These roots disturb the surface and take the water and nutrients, making it almost impossible for grass to grow. Any attempt to mow over the turf that does survive in the presence of surface roots will likely result in both tree and equipment damage.

Delaying Growth

• There are limited options for dealing with extensive surface roots such as those on the silver maple. Pruning the roots might kill the tree, and covering them with soil will likely suffocate the roots -- also eventually killing or severely weakening the tree. Limited success has been recorded with using fabric or plastic root barriers, according to Purdue University's Extension, but it is usually short-lived; most root barriers fail eventually. Using barriers to delay surface root growth, with the knowledge those barriers will need periodic replacing, is one practical solution to limit the silver maple roots' expansion.

Working With the Roots

• As an alternative to, or in combination with root barrier systems, try covering silver maple surface roots with 3 to 4 inches of organic mulch. Mulch provides a permeable barrier that allows for the roots' water and air exchange, while minimizing the trip hazard and unsightly appearance they create. Integrating small plants with limited root systems in between surface roots provides another decorative option. Carefully dig holes in between the tree's surface roots, add compost to each one and then apply 2 to 4 inches of organic mulch between each new plant. Water them well, especially during the first season. You can use these plants in combination with a wider application of mulch to cover the tree's roots.