The Southern Highlands has experienced its fair share of windy weather this winter. A well designed windbreak can be a welcome relief from the wind. Native plants are a crucial choice in developing windbreaks – with correct species selection you can achieve a long-lived, sustainable and beautiful windbreak that not only provides protection from the wind, but also benefits the local ecology.
Unfortunately many windbreaks in the Southern Highlands are poorly designed. A common sight in the Highlands is a single or double row of Leylandii planted as a windbreak – they contribute nothing to our local ecology, do not blend with our natural vegetation and are an extreme fire risk. Windbreaks created with Leylandii or similar species obstruct the wind which then creates turbulence. Very effective wind protection is achieved but for only a relatively short distance on the leeward side of the windbreak. Once out of this minimal protected zone, wind speeds and turbulence increase with intensified risk of damage to crops, gardens or structures. Unless they are pruned regularly within 10-15 years they begin to loose their lower foliage making them ineffective as windbreaks and screens. Leylandii may be effective as a hedge if clipped but would be determined as completely unsatisfactory as a windbreak when the science is considered.
A well-designed windbreak should divert and muffle the wind rather than obstruct it. The efficiency and effectiveness of windbreaks depends upon the height of the windbreak, its width, density and porosity plus its orientation. Porosity would be considered the most influential factor determining the effectiveness of a windbreak. Porosity relates to the amount of air allowed to pass through or be muffled by the windbreak. The denser the vegetation a tree has the less effective it is as a windbreak as it creates turbulence and can actually increase wind speeds beyond the minimal protected zone.
If you are seeking advice as to design and species selection for a windbreak, ensure the advice you act on is not driven by myth, ignorance or prejudice.