When and how to trim
When to trim?
Never cut hedgerows during the nesting season (March to August). Hedge trimming is best left until the end of winter to leave the larder of fruits and nuts for wildlife.
Sometimes it is not possible to get on the field at this time of the year, and on such occasions trimming can be brought forward to early winter. The most important consideration is to avoid such work during the breeding season. Retain ground cover at the base of the hedge over winter for ground-nesting birds such as partridges.
These best practice guidelines are agreed by conservation groups and agriculture departments. Constraints on hedgerow management have been set out in the legally defined Codes of Good Farming Practice, which applies to all farmers participating in an agri-environment scheme or in receipt of Less Favoured Area payments.
Under these guidelines, hedgerow trimming is not permitted between 1 March 31 July in England and Scotland, between 1 March 31 August in Wales, and 1 March 31 August in Northern Ireland.
The flail trimmer - friend or foe?
The flail has made it possible to trim hedgerows at low cost. Modern labour costs would make trimming by hand prohibitively expensive, so without the flail trimmer, many more farmers may have been forced to remove hedgerows.
The flail trimmer is an excellent hedge-trimming tool, although it is only designed to cut through material up to a maximum of 2cm thick. When it is used on thicker stems the result is ragged, split stems. While this looks terrible, most healthy hedgerows are able to survive and recover. This misuse of the flail trimmer, however, leaves the shrubs very vulnerable to attack by fungal diseases, particularly if the flail is used annually.
A different tractor-mounted machine called a circular saw should be used where thicker growth needs to be cut. Where a hedge has become over-mature and is losing vigour, coppicing or laying should be considered. Wide hedgerows are of particular wildlife benefit.
Existing hedgerows can be allowed to widen by cutting a little further out than the previous cut. This also strengthens the hedgerow shrubs.