Could there be something more British than a National Hedge Week? Maybe no one in the world pays more attention to a beautiful, neat hedge than your average UK suburban household. But there’s so much more to the humble hedge than crisp lines and envious looks from the Smiths or Joneses next door.
As the new hedge campaign began this summer, a Royal Horticultural Society investigation found that 40% of UK gardens have a hedge, and between 20% and 25% of urban space is occupied by domestic gardens. This means that we have an important resource to improve the quality of the city’s environment.
The National Hedge Week was created to highlight the immense contribution of hedges in the fight against climate change, biodiversity loss and urban air pollution. With 50% of hedges lost since WWII due to the development of construction and large-scale agriculture, there has never been a more important time for people to start planting and protecting these mini high-level nature reserves in our towns and countryside.
the Climate Change Committee Government advisory body says UK must plant 200,000 km of new hedges if it is to meet its Net zero target 2050. Healthy hedges are essential habitats for biodiversity, supporting over 2,000 species, including the hedgehog and several European protected animals, including the dormouse, the great newt and most bat species.
Above the limit
An important feature of the UK’s suburban landscape, hedges are cheaper and easier to grow compared to other forms of green ‘infrastructure’ such as sedum roofs, vertical gardens or just old trees. This makes it a fascinating subject of study.
We examined the most recent and relevant scientific studies on hedges, covering over 40 species and varieties of popular and widely used plants. Our goal was to establish what is known about the ability of hedges to provide environmental benefits such as cooling and insulating buildings, reducing flood risk, supporting biodiversity, as well as reduction of noise, air and soil pollution. We also looked for signs of potential issues that may arise, such as invasive character, ability to cause allergies, and sometimes difficult to manage.
As plant scientists, we are well aware of the environmental benefits that plants give us, as well as the occasional problems they cause. We also know that the individual varieties differ in the the advantages they can offer. This is due to differences in plant size, canopy structure, and properties of leaves and roots. But most of the research papers look at individual benefits, so we wanted to pull all of this information together as a useful resource.
What we found
This wide range of studies shows that a number of common hedge species have many environmental benefits. The hedge species with the largest overall pool of benefits (cooling, removing air pollutants, reducing flooding) include beech, hawthorn, and holly. No species on our studied list had an entirely negative set of properties, and most offer at least some environmental benefit (e.g. Tinus viburnum and cherry laurel, which support pollinators and provide an excellent noise barrier).
We’ve created a table linking plant species, key traits, benefits, and potential issues to make it easier for people to choose the best-suited species for their own gardens. This is by no means an exhaustive list, but a sample of the available data.
Plant your own hedge
Working in this area of research over the past decade has taught me that the following characteristics are generally linked to more environmental benefits: woody, persistent and perennial planting (i.e. varieties that live longer ), a diversity of planting and the planting of larger plants that flower and grow faster.
So if you are looking to plant a hedge in your urban garden, opt for an evergreen species such as privet, western red cedar or Eléagne, or a good mix of conifers and deciduous trees (which shed their leaves in the fall), such as beech or hawthorn. Prune annually from November to February (so as not to disturb nesting birds in the spring) to encourage more branching and a denser canopy in subsequent years. Also, if you can, let your hedge grow a little taller and deeper – say one meter – as this will increase its ability to capture carbon and absorb air pollution.
If you live in an area where a particular problem is prevalent, such as flooding or excessive traffic noise, you may want to consider species known to excel at solving those problems. For flood problems, try hawthorn; for noise, Euonymus is excellent for attenuating sound. But in most situations planting a good all-rounder such as privet (Ligustrum) or holly (alone or mixed with hawthorn) will allow you and your local wildlife to enjoy the benefits of your own private nature reserve.