Trimming can keep hedges thick and bushy, so they are stock proof and fine wildlife habitats, if carried out in the right way. It will also prolong the management cycle, so the expense of laying or coppicing hedges is kept down. By far the most practical way to trim hedges is using a flail cutter, although on occasion, where larger growth is involved, a shaping saw may be appropriate (although very few farmers or contractors have them).
Trimming must be carried out in the right way to keep a hedge in good structural condition, and to produce good crops of flowers and berries. Ideally hedges should not be cut annually but no more often than once every three years. In Devon soil conditions are such that very few farms are able to cut their hedges after October. Because of this, cutting hedges every other year brings few benefits since there will still be no berries available for birds in the winter. If hedges are cut annually then the cutting height should be raised a few inches for each cut as this will help the structure of the hedges and allow at least some plants to flower and fruit.
Devon Hedge management 3: trimming explains all this in detail. The Centre for Ecology and Hydrology leaflet Increasing the value of hedges for wildlife with relaxed cutting regimes presents the results of new (2015) research. Further information can be found in the Hedgelink publication Hedgerow cutting: answers to 18 common questions. See also The economics of sustainable hedge cutting (although this report was commissioned by the Devon Hedge Group in 1995, its conclusions remain valid).
Hedges should not be cut in the bird breeding season (March to August inclusive) or, for farmers who claim under the Basic Payment Scheme, breach the rules of that scheme. For information on this see The law and other protection .