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Danny LeBlanc

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"To be able to walk under the branches of a tree that you planted is really to you have arrived with your garden. So far we are on the way: we can now stand beside ours."

-- Mirabel Oster

When we think of the natural environment of a forest, we don't often see the forest floor covered in turf. The reverse can be said for the grasslands of the prairies. It is for this reason that we must plan carefully when we include these two natural competitors in our landscape.

All over Metro Moncton a war is being waged between our lawns and trees as they attempt to live in the same space. In most cases, there is no clear victor, but casualties on both sides.

In areas where trees are the first inhabitants, it is difficult to establish an attractive lawn around larger trees and we have difficulty establishing new plants in our front- and backyards.

When trees and turf are used, extra attention must be given to plant selection. An effort should be made to make the trees and lawn compatible.

Grass is a sun-loving plant. Most grass species will not grow well in areas that get less than 50 per cent open sunlight.

However, new varieties with improved shade tolerance are being introduced. Visit your local garden centre if a shade tolerant is required for areas with reduced sunlight, whether it be close to large structures or under large trees.

In areas where the lawn is the primary design feature, select trees 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 is 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 neighbouring 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 two feet of soil.

More important, the majority of fine, water absorbing roots is in the top six 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 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 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.

Maintenance practices for trees and turf are different, and treatment of one can unintentionally damage the other. Fertilizer applied to one plant will also be absorbed by the roots of a nearby plant.

Many herbicides or weed killers that are used in turf can cause damage to trees when misapplied. Watering of lawns is beneficial to trees if watering is done correctly.

Turf growing under or near trees should be mowed at the top of its recommended mowing height. It is a good practice to keep treed areas free of turf and mulched tree pits when trees are grown in the lawn area, expanding the size of the pit as the tree increases in size. Trees and turf are critical components of the landscape.

With the proper management practices trees and turf can add to the landscape. Consult a certified arborist for special situations with trees in your landscape.

* Danny LeBlanc is a certified arborist with more than 20 years experience in the field. Tree Talk appears biweekly in the Home & Garden section. For more information on any of the topics, visit www.treesaregoood.com. To submit a question, e-mail daniel-leblanc@hotmail.com.