Hedgerow management
A Cut Above the Rest
Read more about 'A Cut Above the Rest'
The importance of management
A hedge is a dynamic entity, it will always be trying to develop into a line of trees through natural succession. We can think of a hedge as a woodland edge because often the species we find in a hedge are also to be found as part of a woodland edge. Indeed many of the oldest hedges were formed as woodland was cleared and the woodland edge left as a boundary. If we require a hedge not to turn into a line of trees or we want to keep it thick and stock proof, we want to provide certain habitats for specific species or we just want to keep a hedge ‘neat’ then we need to manage hedges.
Most of the British landscape is man made in that human activity often through farming has created habitats that would all but disappear without management. Heathland, chalk grassland and moorland are just three examples. Hedgerows are no different, they were created by man and require management to ensure their both their condition and their survival.
All hedges need management
Management has to be sympathetically carried out and over management or neglect can be a threat to hedges. Over management is caused by excessively tight trimming over a long period. It is more typically seen on single species Hawthorn hedges which in time form a bottomless mushroom shape and slowly die out.
Many Hawthorn hedges were regularly layed up until the 1950s when there was far more farm labour available. Since then, more often than not they have been cut at the same height each year and this has resulted in slow decline in condition. Even some species rich hedges growing on banks have over time degraded due to excessive cutting.
Repeated cutting at the same height may be done in the name of neatness or for safety reasons along roadsides, but within the hedge each stem is going through a natural ageing process. Stems become larger and often knarled and twisted due to the constant cutting taking place above. In effect the hedge is under stress and constrained by such a regime and if we are not careful we may loose many hedges imperceptibly as they slowly fade away.
At some stage we need to relax the cutting regime and allow the hedge to incrementally increase in height. By doing this we allow the hedge to ‘breath’ and if we act before stems start to die out then a hedge can remain ‘healthy’ for a considerably longer time. It is the density of stems in a hedge that is crucial to this process. If we trim a hedge at the same height for a long time, stems start to die out and even if we then did allow it to gain height options for management are far less. For example a hedge which is allowed to grow may not be able to be layed because the gaps are just too many and even if we were to coppice it to ground level we would have the extra expense of planting up the gaps at the same time. Best of all is to learn to ‘read’ a hedge and allow it to incrementally increase in height in a controlled manner before it becomes over stressed thus keeping all the stems healthy. If we then choose to rejuvenate the hedge either by laying or coppicing we have enough stems to form the basis for the next thick, dense hedge to grow.
At the other end of the scale neglect or lack of management allows a hedge to proceed through its natural life cycle in an uncontrolled manor and the inevitable end of this is an over tall, aging hedge once again with few options for management other than coppicing and planting up gaps. Whilst tall old hedges provide an excellent nectar source from flowers and perhaps ivy and can be an important source of fruit they will ultimetly become unstable and start to collapse. It may also be the case that they turn into a line of trees if trees species are able to colonize. Lines of trees can be important for bats and larger tree nesting birds but a balance has to be found between loosing the rich habitat of a dense hedge through neglect and allowing some hedges to develop into trees.
The life-cycle approach
We need to recognise the life cycle of a hedge. We must learn to allow a hedge to develop in a controlled manner through time never subjecting the hedge to stresses which over the long-term may ruin its condition. As land managers we must try and literally ‘buy’ time by extending the healthy life span of a hedge for as long as we can before we ultimately recognise that we have to intervene and rejuvenate the hedge from the base either through laying or coppicing.
It may be useful to imagine a scale from 1 to 10. Let us say that a hedge that scores 1 is an over trimmed, gappy and dying hedge whilst at the other extreme a hedge that has turned into a line of trees is a 10. In between are all the stages of growth and decline that a hedge may go through during its life. In the ideal world it would be perfect to maintain a hedge between a score of perhaps 3 and 8 that is, between being a healthy trimmed hedge and a healthy tall hedge. As managers we can then base our decisions on slowing down but not altogether halting the natural changes that the hedge wants to go through. By doing this on all hedges on a holding we achieve the ideal mosaic of different shapes and sizes that makes our countryside so special.
Download The hedgerow management cycle.pdf leaflet to read more about how to 'read' a hedgerow and make cost-effective decisions about management to ensure a heathly and long future for hedgerows.
Hedge trimming
There is no doubt that at some stage in the life of a hedge that it will be trimmed. This is done for many reasons including neatness, to thicken the hedge, to keep it under control, and, in situations where there is a health and safety risk for example alongside a road.
As has been said earlier constant long term trimming at the same height places a hedge under stress and can lead to a deterioration in condition but sympathetic trimming can indeed thicken a hedge by creating new points from which growth can ‘tiller’ out.
There are numerous types of tractor mounted hedge trimmer on the market the most common of which is the flail head. This uses hanging blades which rotate rapidly on a vertical plain and cut and mulch woody growth very successfully. They can do a great job but can also create an eyesore when larger woody growth is attempted.
There are knife blade cutters, either a reciprocating knife type or circular spinning blades rather like a flymo mower. These leave a very neat cut and are ideal for light growth with the disadvantage of not mulching up the cut brash.
Finally there is a circular saw blade machine. The first circular saws were developed after the war and were used to reshape overgrown hedges that had been neglected. Today very efficient circular saw blade attachments are available with up to 5 large blades on one head. They are ideal for ‘re-shaping’ a hedge after a period of non intervention and can be used as part of a long term ‘hands off’ cutting regime. Once again the disadvantage is the clearing up of brash but ironically the larger the fallen brash the easier it is to push up and burn with a front loader.
For more information, also see Natural England's hedge cutting leaflet
Hedge cutting: answers to 18 common questions leaflet (NE36)
Hedge planting
For information on hedge planting, please refer to Natural England's hedge planting leaflet
Hedgerow planting: answers to 18 common questions leaflet (NE70)
Cost of management
In 1995 Silsoe College, on behalf of the Devon Hedge Group, compared the costs of cutting hedges once every three years with cutting every year. They also looked at the costs of raising the cutting height a few inches each year, and of leaving hedgerow trees. Their research included the costs of reduced crop yields due to loss of productive land and shading effects. Farms typical of both Devon and the Midlands were covered.
To see the results of this research, download the research paper: 'The economics of sustainable hedge cutting' (pdf 1.5MB).
Also read about the socio-economic importance of hedges.
