Best Trees For Windbreaks
Before we start, a little about what a windbreak actually is. What's the difference between it and a shelterbelt or hedge? What are you looking for in a windbreak?
What Is A Windbreak?
To start with, what it's not. It's not a shelterbelt. A windbreak is a line or double line of trees and/or shrubs, whereas a shelterbelt consists of at least three lines of planting. I'd usually think of a shelterbelt as being planted at at least 1m spacings. To be honest, though, I'm not sure where "windbreak" stops and "large hedge" begins. A windbreak potentially has more large trees in it, I guess, and is not necessarily stock proof. A decent hedge has a good fat bottom to it. Native hedges are typically planted in double staggered rows up to 50cm apart, whereas windbreak rows will be planted wider.
All three - hedges, windbreaks and shelterbelts - provide semi-permeable barriers against the wind. The "semi" bit is important. You don't want too solid a barrier, as might be created by fences or walls, or planting dense evergreens - you'll have problems with wind turbulence.
Why Do I Need A Windbreak?
Too much wind in a garden or orchard has several effects. Most obviously, it creates structural damage to trees and plants. This isn't just to stems, limbs, and fruit and flowers. Wind rock causes even worse problems. Wind also induces a chilling effect, which slows the metabolic activity of plants. On the other hand, you don't want no air flow at all; this will mean pests and diseases. There's also the effect on us; windbreaks can make storms just that bit more bearable, and give some protection to structures.
What Trees Should I Use?
There are all sorts of odd trees for windbreaks used. To declare my interest, I think some of them look rather...peculiar. Eucalyptus, Lombardy poplars, various bamboos - they're not really my thing. Most people planting windbreaks are in rural or semi-rural situations. If you are, have a look at what's around you - use these species and they won't look out of place later on. They'll be good for local wildlife too. By the way, plant your trees as 60-90cm plants maximum size, or they won't stand a chance! They will also need support.
You will need to work out how tall a windbreak you want. Here our prevailing winds are generally southwesterly or westerlies. This might produce problems; if your windbreak is too tall it will shade out some of the area you're looking to shelter. According to the RHS, a windbreak is effective to 10 times its height - so if it's 2m tall, it will shelter up to 20m of ground behind it. Typically this means that trees for windbreaks tend to be bigger than hedge species, or used in combination with them.
My short list might consist of the following:
Medium / Large Trees
Alder: There are three alders to consider as trees for windbreaks - Alnus glutinosa, which is the native one, A. cordata and A. incana.They have slightly different habits but the same helpful characteristics. They grow quickly (around 1m a year) in a wide range of conditions, including cold wet soils. Alders come into leaf early and hold their leaves relatively late, and you can mess about with them - they don't mind drastic pruning. They were traditionally used to protect orchards as they don't carry the same diseases that can afflict fruit trees.
Scots Pine: You could think about a number of pines, but P. sylvestris is our native one. It will grow bigger than an Alder, but more slowly. It's typical of heathland but is regularly seen planted next to isolated farmsteads.
Small Leafed Lime: Tilia cordata is a recent favourite, particularly for a more formal look. Very pretty conical habit, tolerant of a wide range of soils.
Small Trees & Shrubs
Prunus: I'm lumping several plants in here, with similar characteristics. P. cerasifera, Cherry plum, P. domestica subsp. insititia, Damsons, and P. domestica subsp. insititia var. nigra, Bullace. I know - the botany is confusing. All are tough as old boots and excellent windbreak plants for a range of sites. Cherry plums flower very early and grow quickly, although rarely produce fruit (and when they do it's inedible!). Traditional windbreak plant for orchards. A tough damson like 'Westmorland' will give you fruit as well as good performance, as will a bullace.
Hawthorn: Crataegus monogynaisyour basic traditional hedge plant; tough, forgiving, fast growing (hence "Quickthorn") and well behaved (unlike its unruly suckering friend Blackthorn). Good for wildlife, nice blossom.
Sea-buckthorn and Gorse: Not related, but both can be viewed with horror! Many folk spend their lives trying to get rid of them, as in the right conditions they can be invasive. Both Ulex Europaeus and Hippophae rhamnoidesareveryhardy, although they won't grow very tall - gorse to say 2m and Sea-buckthorn rather taller. Sea-buckthorn is salt tolerant, as you might imagine.
Roses: R.canina and the non-native - but naturalised - R.rugosa might be favourite. They're both vigorous, attractive and will tolerate pretty tough conditions. To something like 4m if left alone.