Soil air composition at greater depths is often too poor to support root function. Trees generally lose out in competition for limited nutrients and water in this region when turfgrass is present. Turf competition for water and nutrients can affect any age and size of tree, but is especially detrimental to young trees lacking well-established root systems. Trees with poorly developed root systems suffer from stunted growth. They often succumb to pest attacks and environmental stresses such as drought and nutrient deficiency.
Grasses can chemically retard tree growth .
Some grasses, such as Kentucky bluegrass, red fescue, perennial ryegrass, bermuda, and bahiagrass, release chemicals into the soil which actually suppress the growth of tree roots. Allelopathy is the term which describes this competition strategy. Depending on the type of grass and the tree species, tree growth can be stunted by as much as 65 to 75 percent, even with supplemental watering and fertilization. Tree root distribution . Contrary to the popular belief in deep taprooting, for most tree species, the majority of the root system is actually concentrated in the top 6 to 8 inches of the soil profile where soil aeration is best.