A hedge or hedgerow is a line of closely spaced (3 feet or closer) shrubs and sometimes trees, planted and trained to form a barrier or to mark the boundary of an area, such as between neighbouring properties. Hedges that are used to separate a road from adjoining fields or one field from another, and are of sufficient age to incorporate larger trees, are known as hedgerows. Often they serve as windbreaks to improve conditions for the adjacent crops, as in bocage country. When clipped and maintained, hedges are also a simple form of topiary.
A hedge often operates as, and sometimes is called, a "live fence". This may either consist of individual fence posts connected with wire or other fencing material, or it may be in the form of densely planted hedges without interconnecting wire. This is common in tropical areas where low-income farmers can demarcate properties and reduce maintenance of fence posts that otherwise deteriorate rapidly. Many other benefits can be obtained depending on the species chosen.[1]
Many hedgerows separating fields from lanes in the United Kingdom, Ireland and the Low Countries are estimated to have been in existence for more than seven hundred years, originating in the medieval period. The root word of 'hedge' is much older: it appears in the Old English language, in German (Hecke), and Dutch (haag) to mean 'enclosure', as in the name of the Dutch city The Hague, or more formally 's Gravenhage, meaning The Count's hedge. Charles the Bald is recorded as complaining in 864, at a time when most official fortifications were constructed of wooden palisades, that some unauthorized men were constructing haies et ferts; tightly interwoven hedges of hawthorns.[2]
In parts of Britain, early hedges were destroyed to make way for the manorial open-field system. Many were replaced after the Enclosure Acts, then removed again during modern agricultural intensification, and now some are being replanted for wildlife. As of 2024 in a study using Lidar by the UK Centre for Ecology & Hydrology England alone was found to have a total of 390,000 km of hedgerows, which would span the circumference of the earth 10 times.[3][4]
A hedge may consist of a single species or several, typically mixed at random. In many newly planted British hedges, at least 60 per cent of the shrubs are hawthorn, blackthorn, and (in the southwest) hazel, alone or in combination. The first two are particularly effective barriers to livestock. In North America, Maclura pomifera (i.e., hedge apple) was grown to form a barrier to exclude free-range livestock from vegetable gardens and corn fields.[5] Other shrubs and trees used include holly, beech, oak, ash, and willow; the last three can become very tall.[6] Of the hedgerows in the Normandy region of France, Martin Blumenson said,
The hedgerow is a fence, half earth, half hedge. The wall at the base is a dirt parapet that varies in thickness from one to four or more feet and in height from three to twelve feet. Growing out of the wall is a hedge of hawthorn, brambles, vines, and trees, in thickness from one to three feet. Originally property demarcations, hedgerows protect crops and cattle from the ocean winds that sweep across the land.[7]
The hedgerows of Normandy became barriers that slowed the advance of Allied troops following the D-Day invasion during World War II. Allied armed forces modified their armored vehicles to facilitate breaking out of their beachheads into the Normandy bocage.
Hedgerow trees are trees that grow in hedgerows but have been allowed to reach their full height and width. There are thought to be around 1.8 million hedgerow trees in Britain (counting only those whose canopies do not touch others) with perhaps 98% of these being in England and Wales.[8] Hedgerow trees are both an important part of the English landscape and valuable habitats for wildlife.[8] Many hedgerow trees are veteran trees and therefore of great wildlife interest.
New trees can be established by planting but it is generally more successful to leave standard trees behind when laying hedges. Trees should be left at no closer than 10 metres (33 ft) apart and the distances should vary so as to create a more natural landscape.[8] The distance allows the young trees to develop full crowns without competing or producing too much shade.[8]
Hedges are recognised as part of a cultural heritage and historical record and for their great value to wildlife[9] and the landscape. Increasingly, they are valued too for the major role they have to play in preventing soil loss and reducing pollution, and for their potential to regulate water supply and to reduce flooding.[10] There is increased earthworm diversity in the soils under hedgerows which also help to store organic carbon and support distinct communities of arbuscular mycorrhizal (AM) fungi.[11]
In addition to maintaining the health of the environment, hedgerows also play a huge role in providing shelter for smaller animals like birds and insects.[12] A recent study by Emma Coulthard mentioned the possibility that hedgerows may act as guides for moths, like Acronicta rumicis, when flying from one location to another. As moths are nocturnal, it is highly unlikely that they use visual aids as guides, but rather are following sensory or olfactory markers on the hedgerows.[13] Larkin et al. 2013 find 100% of northwest European farms have hedges, providing 43% of the wildlife habitat there.[9]
Historically, hedges were used as a source of firewood, and for providing shelter from wind, rain and sun for crops, farm animals and people. Today, mature hedges' uses include screening unsightly developments.[10]
Hedges that have existed for hundreds of years are colonised by additional species. This may be useful as a means of determining the age of the hedge. Hooper's rule (or Hooper's law, named after Dr. Max Hooper) is based on ecological data obtained from hedges of known age, and suggests that the age of a hedge can be roughly estimated by counting the number of woody species in a thirty-yard section and multiplying by 110 years.[14]
Max Hooper published his original formula in the book Hedges in 1974. This method is only a rule of thumb, and can be off by a couple of centuries; it should always be backed up by documentary evidence, if possible, and take into account other factors. Caveats include the fact that planted hedgerows, hedgerows with elm, and hedgerows in the north of England tend not to follow the rule as closely. The formula also does not work on hedges more than a thousand years old.
Hooper's scheme is important not least for its potential use in determining what an important hedgerow is, given their protection in The Hedgerows Regulations (1997; No. 1160) of the Department of the Environment, based on age and other factors.[15]
Hedgerow removal is part of the transition of arable land from low-intensity to high-intensity farming. The removal of hedgerows gives larger fields making the sowing and harvesting of crops easier, faster and cheaper, and giving a larger area to grow the crops, increasing yield and profits.
Hedgerows serve as important wildlife corridors, especially in the United Kingdom where they link the country's fractured ancient woodland. They also serve as a habitat for birds and other animals. As the land within a few metres of hedges is difficult to plough, sow, or spray with herbicides, the land around hedges also typically includes high plant biodiversity. Hedges also serve to stabilise the soil and on slopes help prevent soil creep and leaching of minerals and plant nutrients. Removal thus weakens the soil and leads to erosion.
In the United Kingdom hedgerow removal has been occurring since World War I as technology made intensive farming possible, and the increasing population demanded more food from the land. The trend has slowed down somewhat since the 1980s when cheap food imports reduced the demand on British farmland, and as the European Union Common Agricultural Policy made environmental projects financially viable. Under reforms to national and EU agricultural policies, the environmental impact of farming features more highly and in many places hedgerow conservation and replanting is taking place.
If hedges are not maintained and trimmed regularly, gaps tend to form at the base over many years. In essence, hedgelaying consists of cutting most of the way through the stem of each plant near the base, bending it over and interweaving or pleaching it between wooden stakes. This also encourages new growth from the base of each plant. Originally, the main purpose of hedgelaying was to ensure the hedge remained stock-proof. Some side branches were also removed and used as firewood.
The maintenance and laying of hedges to form an impenetrable barrier for farm animals is a skilled art. In Britain there are many local hedgelaying traditions, each with a distinct style.[16] Hedges are still being laid today[17] not only for aesthetic and functional purposes but also for their ecological role in helping wildlife and protecting against soil erosion.
A 'hedgerow management' scale has been devised by an organisation called Hedgelink UK[21][22] ranging from 1 to 10. '1' describes the action to take for a heavily over trimmed hedge, '5' is a healthy dense hedgerow more than 2 metres in height, and '10' is a hedge that has not been managed at all and has become a line of trees.
The term instant hedge has become known since early this century for hedging plants that are planted collectively in such a way as to form a mature hedge from the moment they are planted together, with a height of at least 1.2 metres. They are usually created from hedging elements or individual plants which means very few are actually hedges from the start, as the plants need time to grow and entwine to form a real hedge.
An example of an instant hedge can be seen at the Elveden Hall Estate in East Anglia,[25] where fields of hedges can be seen growing in cultivated rows, since 1998. The development of this type of mature hedge has led to such products being specified by landscape architects, garden designers, property developers, insurance companies, sports clubs, schools and local councils, as well as many private home owners. Demand has also increased from planning authorities in specifying to developers that mature hedges are planted rather than just whips (a slender, unbranched shoot or plant).
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