Windbreak Trees and Plants
Certain trees and shrubs can be useful in their ability to slow, filter, and divert the wind to create more sheltered areas on a property. These species can be grown in exposed locations and are suited to creating landscape features such as shelter belts or wind-break hedgerows. Using plants is one of the most effective ways to manage wind in a garden, farm, or larger property. Plants can filter and disperse strong winds rather than blocking them entirely.
Utilizing Windbreaks Around Your Property
The wind is, of course, one of the elemental forces that shapes our landscapes and environments. Learning how to harness the power it contains can be crucial for sustainable development in the field of renewable energy. Wind can be harnessed to help us in a range of different ways. But while a windy site can be beneficial, there are times when it can be a challenge to growers or in land management.
Utilizing windbreaks can be crucial in ensuring that wind does not threaten or degrade elements in the built and planted environment. Windbreaks are a common feature in permaculture design. But understanding what these are, what they aim to achieve, and using them correctly can be crucial to ensuring that wind is a benefit, not a damaging or erosive force on a site.
What are Windbreaks and What Do They Actually Do?
Windbreaks should not technically 'break' the wind, but rather filter it, and disperse its force. One of the most important things to understand is that an effective windbreak does not stop the wind in its tracks, but rather weakens its force, creating a more sheltered area on its leeward side.
Windbreaks are typically planted features within a landscape, rather than man-made structures, with the capacity to filter and disperse strong winds. They might be carefully planned and positioned in order to:
- Prevent wind from exacerbating soil erosion.
- Create beneficial micro-climate conditions for crops on a farm or in a garden.
- Reduce wind speed to reduce/ prevent damage to plants and property.
- Shelter plants, allowing a wider range of species to be grown.
- Create more sheltered conditions for pollinating insects (in orchards/ forest gardens for example).
- Reduce the costs of heating homes and undercover growing spaces.
- Protect plants from salty winds in coastal locations.
- Protect a site from wind-carried air pollution.
- Mitigate wildfire risks on a property.
- Prevent snow drift, and allow for snow accumulation so its melt can be collected later.
In a windy situation, it is important to understand that placing living plants as wind breaks or shelter belts is almost always better than placing solid man-made structures.
Wind will deviate around solid and impenetrable barriers, while it will be filtered through a living planting scheme to a degree. When solid barriers are created, this can actually increase the turbulence and wind-related issues on the other side.
If the break is too dense or solid, the wind can build up on the windward side and cause turbulence. Heat and humidity can rise on the inside of the windbreak and this can lead to more problems with pests and disease.
In certain cases, features like woven wattle fences, dead hedges etc. can also be beneficial as windbreaks. These have higher porosity, and, like living plants, will let a sufficient proportion of the wind through.
A well-designed living plant windbreak, however, can also do far more. When the right plants are chosen and positioned in the right way, these features can also be a boon for wildlife. They can also potentially provide a range of tangible yields for the farmer or gardener – benefits that a man-made structure placed to block the wind simply could not deliver.
We might also create windbreaks that can provide:
- Habitat and food for local wildlife.
- Forage/ fodder for livestock.
- Nitrogen fixation and/or biomass/ mulch/ composting materials for use in maintaining fertility on a site.
- Edible yields, fuel, crafting materials, etc.
- Increased privacy and screening of unsightly views.
Windbreaks can also sequester carbon, and serve a range of ecological functions delivered by any tree/ shrub based planting.
Types of Windbreaks To Consider
Windbreaks in permaculture design are typically divided into two categories: shelter belts (of larger tree species) and windbreak hedgerows (incorporating shorter trees and shrubs). The scale of a site is one factor that might determine which of these is required, though there are numerous other things to consider.
Shelter belts are windbreaks with a higher profile – typically including tall tree species within them to protect a larger area on the leeward side.
Shelter belts with tree species can be used to manage wind patterns on larger properties, or at landscape scale. They may be rows of trees, or plantings of multiple rows, depending on the requirements of a specific site.
They can be used to provide protection for a home, gardens, or farm fields. Sometimes, tree rows are included in agroforestry approaches on farms, such as in alley-cropping, where arable crops are grown between tree rows.
Windbreak hedgerows are shorter windbreaks made up of tree and shrub species, which can also be very effective within managed systems. Hedgerows can be beneficial for wind-breaking where taller tree species may not be as beneficial.
Though their restricted height will mean that they protect a smaller area on the leeward side, they will cast less shade than a shelter belt of large, mature trees, and can be utilized even on smaller properties.
Determining Where to Place Windbreaks
Deciding where to place windbreaks on your property begins with a thorough understanding of your site and its sectors and flows.
In order to manage wind effectively, you will of course need to understand the prevailing wind direction – the direction from which the winds most commonly come throughout the year, and specific winds, perhaps, that arise during different seasons.
You will also need to understand how winds are affected by the topography in your area, and perhaps how elements in the built environment affect wind flows on your specific site.
Where I live, for example, prevailing winds typically come from the southwest throughout the year.(This is true across the British Isles)
However, due to the landscape surrounding our property, we also frequently experience sea breezes that come up from the southeast, funneling up from a local firth (estuary) a few miles away onto the gentle south-facing hill slope where we live. Buildings also divert winds from the southwest, meaning that they come onto our property largely from the south or southeast.
A hedgerow on the southern side of part of our garden, placed at right angles to the southeast, protects a polytunnel and other plantings from these strongest winds.
Windbreaks – whether shelter belts or windbreak hedges – are best positioned at right angles to the winds you wish to filter and disperse. This may be the direction from which winds most commonly come, but it might also be the direction from which particular cold or damaging winds are known to arise.
But this is not the only consideration when deciding where to place windbreaks on your property.
General things to bear in mind begin with the concept that you need to integrate windbreaks holistically into a design, rather than simply considering them in isolation. To achieve full integration and a holistic design for any site, permaculture practitioners will always:
- Integrate rather than segregate.
- Design from patterns to details.
- Stack functions.
Thinking about these key concepts can help you see how best to incorporate windbreaks into a design, as you determine what your goals are, and how these can best be achieved.
Remember that a windbreak can also become part of a broader design scheme. It can be part of a larger-scale agroforestry approach on a farm, for instance. Or help create boundary planting, or create garden rooms on a smaller property, for example. A windbreak should not just be considered in isolation but as part of the whole.
Be sure to think about all that a windbreak might potentially provide in a specific location. Consider how it might benefit wildlife, you, and potentially other people living close by.
Tips For Windbreak Design
Once you have thought at a high level about what you want a windbreak to achieve and provide, there are certain key tips for design that should help you to achieve your goals.
To design an effective windbreak design, the key things to consider before you even begin to think about species selection are:
- Shape and Form
- Height and Length
- Plant Spacing
Shape and Form
The best shape for a windbreak planting scheme is a triangular cross-section, with the tallest trees or plants at the center, and shorter ones on either side.
Height and Length
The height and length of a windbreak are also very important when it comes to its function.
As a general rule, a windbreak will protect an area behind it of around 10 times its height. (A windbreak hedgerow at is around 1m in height, for example, will protect an area beyond it of around 10m). It will also reduce wind on its windward side over a distance of around 2-4 times its height.
When planning and placing a new windbreak, you should also think about the length of the planted feature in relation to its height. As a general rule, again, a hedge should be at least ten times as long as it is high. So a windbreak hedge that is 1m high should ideally be no less than 10m in length.
Adhering to this ratio will help to reduce turbulence around the edges of the windbreak. If the hedgerow will be shorter, then this turbulence is something that you may need to take into account.
Plant spacing is one of the most important factors in creating an effective windbreak hedge. Depending on the plants that are chosen, a spacing of 30-90cm between the main structural plants is generally considered to be optimal.
If choosing larger trees for shelter belts, species are typically placed 2-4m apart, with shrubs between them and to the leeward and windward sides.
After the primary plants have been placed, you can position smaller companion plants to either side and begin to form the optimal triangular shape.
Choosing Plants for Windbreaks on your Property
Honing in from patterns to details, the next thing to think about is which plants you will include within your windbreak design. Species selection is of course an important part of the process of designing and creating a windbreak.
Some key things to bear in mind are that you should aim to:
- Select For your Specific Location and Site.
- Enhance Biodiversity.
Choosing the Right Plants for Place
The best place to begin when choosing species for your windbreak is with native plants, which will be best suited to the conditions where you live.
Of course, it is important to think about climate, microclimate, and soil, and to consider all the characteristics of the location. It is only when you understand your site that you can choose the right plants for the right places.
Typically, you will begin by choosing the key tree or shrub species. And will then progress to choose lower-tier plants for the lower stories of vegetation on either side of the tallest plants at the center of the design.
The species you choose for your hedge will, of course, depend very much on your goals for the design. Be sure to think about what you want to achieve, and what each of the species you are considering can provide.
Boosting Biodiversity in Your Windbreak
Diversity is key. The more beneficial interactions you can generate between the plants themselves, and between plants and animal life, the more resilient and wildlife-friendly your hedgerow will be.
For year-round function and appeal, for you and wildlife, it can often be a good idea to choose to include both deciduous and evergreen trees and shrubs in the scheme.
Deciduous trees and shrubs create permeable barriers to slow wind speed. Evergreens provide shelter year-round, but if planted densely and alone, they can act as too solid a barrier. So planting both deciduous and evergreen species can be a good idea.
Windbreak hedgerows are common where I live, often including species such as Crataegus monogyna (hawthorn), Corylus avellana (hazel), Sambucus nigra (elder), Carpinus betulus (hornbeam), Alnus glutinosa (alder) and Rosa rugosa (rose). Ulex europaeus (gorge) hedges are also very common along the banks of the firth and around the nearby coast.
Trees commonly used in larger shelterbelts include Fraxinus excelsior (ash), Acer pseudoplatanus (sycamore, non-native), Oaks (Quercus petraea etc.) Sorbus aucuparia (rowan/ mountain ash), along with pines, firs, and spruce not native to this bioregion.
(We noted after severe storms in recent years that non-native coniferous tree plantations were the areas where many trees came down, while native broadleaf trees largely fared well. Though native evergreens – especially the Scot's pine – are very useful in different parts of Scotland, the old Caledonian Forest did not extend into the region where I live, which was historically a mixed broadleaf forest).
If there are windbreaks and shelter belts in your area, observing those that use native species and that work well where you live can help you learn through observation and move closer to finding the right species selection for you and your needs. Looking at the character and species composition of native ecological systems can often be a good starting point for species selection.
However, it can also be worthwhile considering non-native plants where these fill ecosystem niches and deliver the desired functions when used within your windbreak design.