Design

A shelterbelt planting is a long-term investment, and careful planning can improve benefits and help avoid problems.

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Shelterbelts require several kinds of trees and shrubs with different growth characteristics to provide foliage density at various heights over a period of years. As trees age, their form and crown characteristics change. The ability of a tree planting to provide protection depends on a combination of tree and shrub species characteristics such as shelterbelt height, density and longevity.

Height influences the extent of the protected area. The taller the shelterbelt, the greater the area protected. For a quick effect, plant fast-growing trees that reach maximum height in a short time. Since fast growers are usually also short-lived, you should also plant slower-growing trees that mature later but remain functional for a long time. Density influences the extent of downwind protection.

Young trees provide foliage density near the ground, at a height range of 0-3.0 metres (m). As the trees mature, density near the ground will have to be provided by thick growing shrub species. Most conifers have dense, compact tops that retain foliage throughout the year.

In contrast, deciduous trees and shrubs lose foliage in the fall causing shelterbelts to have lower densities in winter than summer. Foliage density in the middle level of shelterbelts, 3.0-5.0 m, will be provided by the fast-growing broadleaf trees. As the broadleaf trees age and grow, conifers begin to assume the mid-level density function.

An effective shelterbelt is composed of five rows of trees and shrubs. If limited space prevents planting five rows with adequate space between rows, it is better to plant fewer rows than to crowd the trees. Three rows, with room to grow, will result in better long-term results than five crowded rows.

When there is not even enough room for three rows, a narrow shelterbelt of two rows of dense conifers, provides the most practical protection under the circumstances.

Staggering the trees, so they are not directly behind the tree in the adjacent row will optimize protection.

Developing a sketch of the planting area helps the planning process. When designing your shelterbelts the following are important considerations to identify:

  • Note orientation (north) on the sketch pad
  • Prevailing or troublesome winds
  • Locate existing buildings or structures and any future developments
  • Note all distances between structures
  • Identify property lines, fences and roads
  • Locate existing trees (bluffs or planted rows)
  • Identify power lines/utility service lines (include buried lines)
  • Identify trouble areas where there is snow build up, flooding, soil problems, steep slopes or lagoons
  • Indicate landscape features (hills, water areas, stubble, grass, summerfallow)
  • Include location of new tree rows, species selection, row spacing and length of rows
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