John Beech – Land Management Adviser
Mature trees within a hedgerow network are an important feature in the countryside. This is where land managers across generations have allowed single hedgerow plants to grow to their potential, alongside hedgerow plants that are coppiced, laid, and managed to create a boundary. Hedgerow trees have no particular value in terms of land management, but have huge value for wildlife and for the landscape.
Traditionally Elm, Ash and Oak trees were the dominant hedgerow tree species reaching heights of up to and over 30 metres tall, towering above the hedgerow corridors. Saplings that are allowed to grow higher than the surrounding hedge do not need to compete for light and therefore grow and spread their canopy high and wide up into the air. This provides a wonderful habitat kingdom for many species of wildlife, free from the clutch of ground based predators. Such trees act as key wildlife ‘stepping stones’ between woodland habitats and across a mixed landscape.
The intensification of agriculture in the latter half of the 20th century including increasing field sizes resulted in the loss of thousands of miles of hedgerows along with their hedgerow trees. The outbreak of Dutch elm disease from the late 1960s onwards removed some 20 million elms from our countryside, mostly from hedgerows. It is therefore quite rare now to find a mature Elm tree within a hedgerow. Similarly Ash trees are now threatened by Chalara dieback.
In 1998 there were an estimated 1.8 million hedgerow trees in Britain (CPRE survey). Many of our over mature hedgerow trees today are beginning to die and slowly retrench. There is an adage that an Oak tree takes over 200 years to grow and then 200 years to die.
To check the loss of hedgerow trees we need to be planting new ones to replace the ones that are dying back. The 1998 survey revealed that only 1% of hedgerow trees were in the youngest age class (1-4 years old). Without successional planning there is a danger that these key features will be lost for good from the landscape and the disconnection between farmed land and semi natural woodland will become more marked than ever. It takes a leap of imagination but by planting now land managers will be leaving their mark on the landscape for their children.
Trees take time to grow. Native wildlife species use hedgerow trees but birds, bats and butterflies in particular favour mature hedgerow trees.
Tawny Owls take advantage of mature trees both as nesting sites and day roosts usually hiding close up against trunk. From a tree perch owls can see the movement of their potential prey on the ground below them. Bullfinches clamber amongst the branches searching for seeds, buds and insects. Treecreepers and Nuthatches use their acrobatic skills to forage for insects, nuts and berries and Woodpeckers drill away into the deadwood high in the canopy to make a home and feast on any tiny invertebrates in the wood. Butterflies such as Hairstreaks forage for honeydew from aphids and lay their eggs high up in the Oaks and Elms. Rich lichen communities also grow on the branches of old hedgerow trees.
In some of the older trees, holes and crevices provide ideal habitats for a variety of bat species. Around three quarters of British bat species are known to roost in trees. Bats use different parts of the tree for different reasons, depending on the time of year and temperature. In the summer bats use the higher canopy sites to have their young in warmer temperatures. In winter, they move deeper and lower into the tree to hibernate. Trees such as Oak, Beech and Ash are particularly suitable for bats, but any hedgerow tree has potential for a bat roost – especially if it has cavities in the trunk or branches, woodpecker holes, loose bark, cracks, splits and thick ivy. In Britain, all bat species and their roosts are legally protected by law.
We’re working on enhancing wildlife corridors and connections through our habitat connectivity initiative, and as part of this we’re actively encouraging the planting of hedgerow trees where appropriate. With the loss of Elm and the threat to Ash, Oak is now the main species being planted in the North York Moors to become the hedgerow trees of the future. With good care and maintenance the trees should grow into vigorous specimens.
To foster hedgerow trees:
- Select suitable saplings from within an existing hedgerow and add a tree tag to the top of it. This shows/reminds the person who cuts the hedge to leave this strong sapling to grow into a mature tree.
- Alternatively, plant a hedgerow tree adjacent to an existing hedge to add variety and height. This has the added advantage of widening the hedgerow and enables useful wildlife buffer strips to develop along the hedge bottom. If there is an existing gap within a hedgerow that is wide enough to accommodate a hedgerow tree then plant a new tree there.
- Try to avoid uniform planting and instead plant the new trees at irregular intervals along the hedge line. Planting two or three together may also be suitable for instance if a site is next to a field corner.
- Plant trees with local provenance that will be used to the local conditions and be more likely to flourish.
- It is best practice to add a tree guard or tube attached to a stake to protect a tree in its early years from stock, rabbits or deer. A mulch mat around the base of the tree helps to keep the weeds down. This will give the tree every chance to grow strong and straight.
Practical help and advice can be provided by the National Park Authority. Contact us.