There may be a battle brewing in your backyard between your trees and your grass. Trees and turf tend to be mutually exclusive — you won't see many trees growing in the prairies or grasslands, and grass is uncommon on the forest floor.

Urban landscapes represent an unnatural ecosystem in which we force two somewhat incompatible plant types together and expect optimum performance from each. Trees and turf compete for sunlight, water, nutrients, and growing space. Turf roots typically win the below-ground battle. But the dense shade of a tree can be too much for turf, enabling trees to win the aerial war. Shade leads to reduced grass density, increased root competition, and increased weed invasion.

In order for turf and trees to cohabitate, here are some areas you should consider:

• Mulch — The most simple maintenance recommendation is also the most important. Mulching root areas of trees is one of the least expensive but most beneficial things you can do to enhance tree health and minimize competition with turf. Mulch helps retain soil moisture, moderates soil temperature, and reduces competition from weeds. Organic mulch can help condition the soil and improve microbial activity. Learn how to properly mulch a tree.
  
  
• Pruning for light penetration — This should be considered, keeping in mind that it is not a permanent solution. Remember, trees will grow into voids created by pruning. That's why the rule of thumb is to not remove more than one-fourth of the foliage-bearing crown in a single pruning.
  
  
• Root Control — Some trees tend to form surface roots, which can be a major problem in lawns. Homeowners always want to know to what extent they can prune or remove tree roots without killing the tree. Because cut roots tend to develop more roots, root pruning is generally not a permanent solution.
  
  
• Fertilization — There is a long-standing, but inaccurate, belief that trees must be "deep root" fertilized. This notion is associated with the myth that the root system is an underground mirror of the crown. Because most of the absorbing roots are actually in the upper few inches of soil, it makes little sense to place the fertilizer deeper. If you are fertilizing your lawn near trees, the trees may not need supplemental fertilization.
  
  
• Mowing — Most people don't realize the degree of damage that can be caused by the bumping of a mower or the whipping action of a nylon string trimmer. A tree's bark can only provide so much protection against these devices. Young, thin-barked trees can be damaged almost immediately. In the worst case scenario, trees may die. Those that are not killed will be stressed, and wounds may serve as entry points for diseases, borers or other insects.
  
  
• Chemical treatments — Herbicides, especially broadleaf weed killers, are often used on lawns. It is important to remember, however, that most trees are broadleaved plants and can be injured or killed if high enough doses reach them. Homeowners must keep in mind that "weed and feed" fertilizers contain herbicides, which can damage trees.
  
  
• Achieving a balance — Trees and turf can peacefully coexist, even thrive, in a landscape. Armed with an understanding of how each affects the other, a homeowner can modify the environment and the maintenance procedures to optimize the growing conditions for both.

One of the best ways to know if you are making wise tree decisions is to educate yourself on some basic principles of tree care or hire a professional certified arborist to assess your needs.

More information:

• Treesaregood.com - offers consumer information about trees.
• International Society of Arboriculture - find a certified arborist in your area.
• City Forester - can diagnose problems with trees located within the city right-of-way along the street. Call 913/327-6639.