Trees and Turf

Discussion in 'Lawn Mowing' started by Coffeecraver, Oct 1, 2004.

  1. Coffeecraver

    Coffeecraver LawnSite Senior Member
    from VA.
    Posts: 793

    Woody plants and turfgrasses are both 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 affects 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.

    Selection
    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 compat-
    ible. Grass is generally a sun-loving plant. Most grass species will not grow
    well in areas that get less than 50% 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 (trees that 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 is present.Remember, tree roots get larger as the tree gets older.

    Competition
    Trees, shrubs, ground covers and lawn grasses all require sunlight, water and
    rooting space for growth. Each plant in the landscape competes with the
    neighboring plant 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. Since perennial woody plants
    increase in size each year, they require additional space over time. The land-
    scape 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 out-compete 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 :waving: 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. This 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 2-4 inch layer of wood chips, bark, or other organic material over the soil under the drip line is recommended because it:
    • Helps to retain soil moisture
    • Helps to 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).

    Maintenance Practices

    Maintenance practices for trees and turf are different, and treatment of
    one can unintentionally damage the other. Because tree and grass roots exist
    together in the upper 6-8 inches of the topsoil, treatment of one may
    damage the other. Fertilizer applied to one plant will also be absorbed by
    the roots of a nearby plant. Normally this is good, but excessive fertilization
    of either trees or turf can result in tree-crown or grass-blade growth
    greater than that desired.

    Many herbicides or weed killers that are used in turf can cause severe
    damage to trees when misapplied. This can occur on windy days, causing
    the drift to fall on non-target plants or on hot days when the herbicide may
    vaporize and diffuse into the air. While most herbicides do not kill tree
    roots, some, such as soil sterilants and a few others, do. Herbicides that can
    cause tree damage have statements on their labels warning against using the
    product near trees.

    Watering of lawns is beneficial to trees if the watering is done correctly.
    Trees need the equivalent of one inch of rain every seven to ten days.
    Frequent, shallow watering does not properly meet the needs of either trees
    or turf and can be harmful to both.

    Turf growing under or near trees should be mowed at the top of its
    recommended mowing height. Mowing off no more than 1/3 of the grass
    blade's height and letting the clippings remain on the lawn will do much to
    ensure a healthy and vigorous lawn. In an ideal situation, tree and turf
    maintenance would be handled by the same individual in order to maximize
    the benefits of all maintenance practices.

    Special Situations

    • Placing fill dirt around existing trees. Fill dirt is frequently added around
    existing mature trees so that a level or more visually desirable lawn can be
    established. Fill dirt changes the ratio of oxygen to carbon dioxide around
    tree roots and the roots may die. Consult a tree care expert before adding
    fill or constructing soil wells around tree trunks.
    • Establishing lawns around existing trees. Preparation of a seedbed for
    lawns requires disruption of the upper 4-6 inches of topsoil. This soil
    contains the feeder roots of trees. Damage to tree roots often results in
    declining tree tops.
    • Creating tree root buffers with turf. A sufficiently wide strip of
    turfgrass between trees and hard surfaces such as building foundations,
    sidewalks and roads can help to reduce the potential damage caused by
    tree roots as well as provide an area where water and nutrients can soak
    into the soil and be beneficial to both turf and trees.
    • Lawn watering in arid sites. Homes are sometimes built in woodlots. In the
    West, the watering that is required to maintain grass is especially damaging
    to dryland trees. Excess water at the tree trunk encourages growth of
    fungi that can kill trees.

    Thin turfgrass growing around trunk-scarred weak trees does not need to
    be a common sight in the landscape. With proper planning, proper plant
    selection and placement, and reasonable management, the many and varied
    benefits of both trees and turf can be readily achieved.
     

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