How and Why To Plant Coastal Shelter

Windbreaks and Hedges

Having protection from salty gales will greatly increase the possibilities for a coastal garden. With more shelter from the wind you can grow a far wider range of plants and you can go out into the garden without being blown over so often.

Wind is moving masses of atmosphere, see the Met Office’s definition here. A simplified definition could be that air is at different temperatures in different places, as air warms it expands, raising it’s pressure and causing it to be ‘sucked’ towards areas of cooler, lower pressure, air. On a weather map those dense isobar lines you see when a storm is coming indicate a steep pressure gradient between areas of high and low pressure atmosphere.

For maximum effect a hedge or windbreak should be perpendicular to the prevailing (SW) wind, protection against wind from other quarters is nice too but will be useful less often. Put simply the wider, taller and deeper any protective screen from the wind is, the more protection it will give.

The sheltered area behind a hedge or windbreak is proportional to the height of the barrier. A short hedge (<1.5m / 5’) will be more of an ornament than a practical shelter as the lower air pressure in the lee soon draws the wind back to ground level.

With a higher hedge or windbreak it takes further in the lee for the wind to draw back to ground level.

Wind will also curl in around the sides of a windbreak or hedge, so the wider a barrier as well as higher, the more ground it will protect behind.

It is better to make your shelter somewhat permeable to the wind, slowing the wind rather than stopping it. With a solid barrier like a wall the pressure difference between the air passing over the barrier and the air behind it is significant and this creates lots of damaging turbulence as the air tries to equalise the pressure.

A multi-layered windbreak is the ideal solution where space and budget allows. The canopies of the trees and bushes will filter rather than stop dead the wind. Therefore the pressure difference between the lee and the windward side is less than with a solid barrier, leading to less damaging turbulence.