The International Society of Arboriculture publishes in its tree care website the following guidelines on planning for a beautiful, valuable landscaping for all needs. At ABOVE AND BEYOND – TREE SERVICE we can help you planning your next tree project! Contact us if you have any questions!
Woody plants and turfgrasses are critical components of design plans for homes, offices, and parks. Trees and turf offer distinct personal, functional, and environmental benefits. Personal preferences for color, fragrance, and form should complement the functional properties of size, shape, density, and placement of plant material.
We’ve all seen thinning grass under large shade trees, large surface tree roots that cause safety hazards and mowing obstacles, young trees that don’t seem to grow, and tree trunks badly damaged by lawn mowers or string trimmers. All of these undesirable effects can be caused by trees and turf growing too closely together.
Turfgrasses provide many of the same environmental benefits as trees. They
- change carbon dioxide into the oxygen we breathe
- cool the air by changing water into water vapor
- stabilize dust
- entrap air polluting gases
- control erosion
Turfgrasses, in addition to being environmentally beneficial, are attractive in formal and informal designs. There are many advantages to combining trees and turf in the landscape.
When trees and turf are used in the same areas, extra attention must be given to plant material selection in addition to the usual hardiness, climatic, and soil needs. An effort should be made to make the trees and lawn compatible. Grass is generally a sun-loving plant. Most grass species will not grow well in areas that get less than 50 percent open sunlight; however, new varieties with improved shade tolerance are being introduced. Consult your garden center specialist or sod producer for recommendations of shade-tolerant grasses for your area.
In areas where the lawn is the primary design feature, select woody plants that do the least damage to grass growth and maintenance. The woody plants should be small, have an open canopy (to allow sunlight to penetrate to the ground), or have a high canopy. Select trees that do not root near the soil surface; surface rooting is most serious where shallow topsoil or composted clay soils are present. Remember, tree roots get larger as the tree gets older.
Trees, shrubs, ground covers, and lawn grasses all require sunlight, water, and rooting space for growth. Each plant in the landscape competes with neighboring plants regardless of type or species. Some even produce chemicals that are exuded from roots to restrict growth of nearby plants. For each plant to do well, it must have adequate space. Because perennial woody plants increase in size each year, they require additional space over time. The landscape design should provide adequate space for these plants to mature.
While shade is the biggest, most obvious problem trees create for turf growth, a tree’s roots also contribute to poor turf performance. Contrary to general thinking, most tree roots are in the top 2 feet of soil. More important, the majority of fine, water absorbing roots are in the top 6 inches of soil. Grass roots ordinarily occupy a much greater percentage of the soil volume than tree roots and outcompete them for water and nutrients, especially around young trees. However, grass root density is often much lower in areas where trees were established first. In these situations, tree roots compete much better for water and nutrients and prevent or reduce the success of establishing new turf.
Competition is especially important when transplanting, seeding, or sodding. The newest plant in the area must be given special treatment and must receive adequate water, nutrients, and sunlight, which frequently means that competing sod should be removed from around transplanted trees and shrubs or that some of the lower branches should be removed from existing trees above a newly sodded lawn. In any case, do not do any tilling around trees.
Mulching is an alternative to turf around trees, and its use eliminates potential competition. A 2- to 4-inch layer of wood chips, bark, or other organic material over the soil under the drip line is recommended because it
- helps retain soil moisture
- helps reduce weeds and controls grass
- increases soil fertility when mulch decomposes
- improves appearance
- protects the trunk from injuries caused by mowing equipment and trimmers that often result in serious tree damage or death
- improves soil structure (better aeration, temperature, and moisture conditions)