Windbreaks and Shelterbelts
The most important thing to understand about a windbreak is that the aim is not to stop the wind: you are only trying to slow it down. A solid ‘wall’ of trees will cause wind eddies on the leeward side and actually increase the windspeed, whilst at the same time putting pressure on the root systems. You want to gradually slow the wind down through a mosaic of predominately broadleaved trees.
Wind has a nasty habit of finding its way around the edges of skimpy windbreaks, so when planning a windbreak, think generously! A well-planned windbreak will provide a shelter effect out to an area about 10 times its height. So if your windbreak is 5m tall, your will get decent shelter 50m back at a point in the middle of the hedge. The wider the windbreak, the larger the shelter ‘triangle’ will be. As a minimum, plant two staggered rows of deciduous trees on the windward side of the windbreak with 1 metre between trees and 1 metre between the rows. Then 2 metres back, plant conifer trees at 2 metre spacing. The thicker the windbreak is the better, so if you have space then plant some shrubs in front of the windbreak, add in another row or two of evergreen trees and plant some more rows of deciduous trees on the sheltered side of the windbreak.
Which trees should I choose for my windbreak?
The structure of the windbreak is more important than the tree choice, remembering that the idea is to slow the wind down gradually vertically and horizontally. Most people go for a 20% evergreen/80% deciduous mix because that works well for slowing the wind down and the windbreak tends to look quite natural. It is best to choose trees which are best suited to the site conditions and the tree finder can help you select for that. If you want keep with windfirm trees, then for deciduous trees you could choose beech trees, hornbeam trees, sycamore trees, birch trees, sweet chestnuttrees, ash trees, oak trees and cherry trees. For conifer trees, try scots pine trees, larch trees and douglas fir trees.