Assess the site carefully to establish the type of windbreak needed and the dimensions and positioning necessary to provide shelter.
Type
To be effective, windbreaks must be semi-permeable, ideally filtering 50-60 percent of the wind to reduce its strength. Solid barriers are unsuitable, leading to damaging eddies of wind on each side.
Windbreaks can be living or artificial. Living windbreaks of planted trees and shrubs are most attractive and long-lasting but artificial screens give immediate protection. Artificial screens can be used alone or in conjunction with living windbreaks to provide shelter while they establish.
Solid fences are unsuitable for slowing wind but any fence with 50-60% porosity, such as woven hurdles of willow or hazel, will be effective. Woven or extruded plastic netting is available to the amateur gardener but, for screens over 1.5m (5ft), professional heavy-duty plastic strapping such as ‘Paraweb’ may be needed.
Dimensions
A windbreak will significantly reduce wind on its leeward side to a distance of ten times its height. Windbreaks should be wider than the area needing protection, or should be extended down the sides, to prevent wind slipping around the sides.
Positioning
In general, windbreaks should face the prevailing winds (which come from the south-west in the UK) but in some situations the priority may be protection from damaging, cold, north and easterly winds.
The lie of the land (topography) affects wind direction and must be taken into account. Hilly sites may need shelter on several sides as wind can come over a hill and also produce gusts round the sides. Wind can also be funnelled along valleys, between lines of trees or tall buildings, creating what is known as a 'wind tunnel'.
