Information on how to manage a hedgerow for biodiversity

Why does the National Park support planting and management of Hedgerows?

Hedgerows are integral to the character of the National Park. They are a much-loved feature of this managed landscape that epitomise the coexistence of farming and nature. We don’t know exactly how much hedgerow we have, but one estimate puts it at 3,500 miles in the National Park. If the average density is 5 plants per yard, that represents 30 million trees and shrubs.

Farmers have created hedgerows to demarcate their land, create stock barriers and provide shelter. They may have been created in Wales as long ago as the bronze age, and many surviving hedges are centuries old. Hedgerows often give insights into the cultural history of our landscape, for example marking ancient monuments or outlining where old farms were situated.

Hedgerows are included in the Environment (Wales) Act (2016) Section 7 list of habitats of principal importance for the purpose of maintaining and enhancing biodiversity in relation to Wales. They bring many benefits to nature and form one of our largest nature reserves. Across the UK, more than 600 plant, 1,500 insect, 65 bird and 20 mammal species use hedgerows – for food, shelter and to move between areas. Mature trees—sometimes pollarded—are often found in ancient hedgerows. The verge or bank beneath the hedge may contain bluebells, wood anemones, cow parsley and greater stitchwort, and the hedge itself may be a rich mixture of woody shrubs such as hazel, dogwood and guelder rose. Hedgerows are both habitats in their own right, as well as corridors for wildlife, that create vital connections between other, more isolated habitats.

Hedgerows lock up huge amounts of carbon dioxide and store it in their roots, branches and leaves, and in the soil. They have been estimated to offset a quarter of all the yearly emissions from farming in the UK: about 13 million tonnes of carbon per year. The Climate Change Committee has recommended that the extent of hedgerows be increased by 40% as part of measures against the climate emergency.

Hedgerows also provide other ecosystem services, including stabilising soil and reducing surface water run-off, which can wash soils and nutrients into our rivers. As the pattern of extreme weather events changes, the role of hedgerows in providing shelter to livestock is becoming more important. In urban areas, hedges can help capture air pollution and reduce summer temperatures.

Bannau Brycheiniog, in partnership with Stump up for Trees and the Woodland Trust, are implementing the project “Traditional Boundaries of Wales”, which supports farmers to restore and revive hedgerows in the Park. The project supported the planting of three kilometres of new hedgerow – 13,000 trees and shrubs – in 2023. The Park will also work with farmers to improve the management of hedgerows as biodiverse habitats, through support for training and hedge laying.

What is a healthy hedge?

Hedgerows are making a come-back. A huge extent of hedgerow was lost between 1950 and 1975, as farmers were encouraged to exploit as much land as possible for food production, and the losses continued into the new millennium. The total length of managed hedgerows in the UK decreased by 6.1% (26,000km) between 1998 and 2007. However, changes to agricultural policy have placed greater emphasis on protecting habitats on farms and a steady revival of hedgerows is underway. Hedgerows are also now protected by the Hedgerows Regulations (1997), which require landowners to notify local authorities if they want to remove hedgerows. Click here for information on planning in the National Park.

The best hedgerows for wildlife have a mixture of woody species, like hawthorn, blackthorn, field maple, and hazel, with the occasional ramblers, such as rose, holly, and honeysuckle. Healthy hedgerows are dense, often a bit wild, and allowed to gradually grow in height for several years. This prevents stems from dying, keeps them dense, and keeps the hedge healthy for longer. However, lack of management is also a threat to hedges and leads to tall, aging hedges with many gaps and at risk of collapse. Thin lines of tall, mature trees that are disconnected at ground level can be found around the Park, providing evidence of what happens to hedges when they are left unmanaged. These provide other habitat—nesting space for birds and flight paths for bats—but they represent a loss of the habitat associated with a dense hedge.

Hedge laying is a traditional practice that is still carried out in the Park, contributing to hedgerow health and biodiversity. Hedgerow trees reach a certain height and then are partially cut near the base, laid horizontally, and woven to form a strong, stock-proof barrier: a living fence. The discerning eye can even identify locations in the Park according to the unique local styles of hedge laying.

Maintaining a healthy hedge

Many farmers manage their hedgerows well, and in corners of the National Park the practice of hedge laying is still practiced. However, many are not maintained in a state that allows biodiversity to thrive. Hedgerows need management, which comes at a cost, and both over-management and neglect can be a threat. Farmers sometimes over-manage their hedgerows in their effort to keep them tidy, or for safety reasons, such as to maintain visibility along roads, but when they are trimmed too tightly for several years, they can become top-heavy with many gaps.

The Good Agricultural and Environmental Conditions (GAEC) of the Common Agriculture Policy outline some requirements for hedgerow management, including when hedge cutting and laying may and may not be carried out. The National Farmers Union provides a summary of rules and guidance on hedge trimming.

Further advice on hedgerow management is available from Hedgelink, including these 12 management principles:

  1. Consider the Complete Hedge
  2. Promote joined-up Hedge Landscapes
  3. Create Structural Diversity across the Farm
  4. Encourage a Range of Shrubs and Trees
  5. Keep the Shrub Layer Dense
  6. Allow Shrubs to Flower and Fruit
  7. Look after Mature Trees and Encourage New Ones
  8. Encourage Out-Growths
  9. Encourage Thick Basal Vegetation
  10. Encourage Flower-Rich Margins
  11. Manage Ditches
  12. Keep Fertilisers and Pesticides away from Hedge Bases and Ditches

Hedgerow condition can be assessed according to its structural health and its potential benefits to wildlife. Structural health includes the height, width and thickness (number of gaps) of the hedge as well as associated features (e.g. presence of a ditch or bank). Indicators of the benefit to wildlife include hedgerow plant diversity, presence of wildlife, and how well the hedgerow connects different habitats or other hedges.

The Hedgelink website includes 9 advisory leaflets for particular animals or assemblages of animals associated with hedgerows, including bats, bumblebees, dead wood insects, ditch invertebrates, dormice, grass snakes, hairstreak butterflies, hedgehogs, and pollinators.

Creating new hedgerows

Many farmers in the National Park are planting new hedgerows and there are number of grants available for this, including from the National Park under the Traditional Boundaries of Wales project. Hedges serve several purposes, which determines where they are best located: for example, filling gaps and providing connections between other hedgerows and woodlands, demarcating historic boundaries, or creating a windbreak.

Hedgerow plants are best planted between late October and early March, and usually the earlier the better, so that the plant can establish before the onset of spring, although clay soils and poorly drained soils may suit planting in March.

Selection of suitable species depends on the geology, altitude and climate as well the purpose of the hedge, and the preferred species changes from east to west in the Park. In general, the more woody species in the hedge, the better it is for wildlife. Different schemes may stipulate different planting densities, but in general 6-7 plants per metre in a 2-metre-wide hedge is acceptable. Plants that do not survive the first year will need to be replaced. Fencing and tree guards may be necessary to protect against damage from sheep, deer and rabbits, but this can be gauged according to local conditions to avoid unnecessary costs and complications. Farmers are encouraged to maintain mature trees at intervals in their hedge and these may need to be tagged for protection when the hedge is first planted. Further guidance is available from the Long Forest project.

Other Resources:

Hedgerow | North Wales Wildlife Trust

A history of hedges – The RSPB

Hedgelaying | Museum Wales

Hedgerow Management Advice | Hedgelink