Notes from an award winning Farm – Hedges
Hedges are an emotive subject these days. Farmers are much criticised for removing them, or cutting too hard those that remain. Yet hedge loss is certainly not confined to this century. The process of removing hedges to make fields larger has been going on for centuries. Most hedge loss occurred during the second half of the C19 when the field layout was remodelled to suit Victorian requirements. Farm layout has always reflected the economic and technological demands of the age.
We plant new hedges now because they are still needed. With a milking herd or beef cattle to feed, temporary grass leys are part of the arable rotation. They are grazed after being cut for silage, so we need to maintain some form of stock proof barrier round almost every field. We find hedges as cheap to maintain and much longer lasting than fencing which we continue to replace with hedging. These then provide some shelter for stock. To gain these agricultural advantages we need to keep them in good condition, tall and thick, which is best for wildlife too.
Wildlife uses hedges both as habitat and highways, or corridors in current jargon. Like roads for traffic, the layout or pattern of these corridors needs careful planning. If the hedge verges are treated sympathetically, the field edge becomes part of both habitat and corridor, turning the latter into the wildlife equivalent of dual carriageway. Hedge and field edge together are now called the field margin.
The pattern (the way hedges link together the various habitats on the farm) is one of the most vital features of farm conservation. Wildlife needs to be able to move between habitats along routes that offer some degree of shelter and protection at all times of year. Small pockets of wildlife in isolated habitats are very vulnerable, and recolonization is difficult. Hedges provide a major component of wildlife corridors.
Incidentally, planting new hedges is quite costly, both in money and labour. The hedge needs protection from stock on both sides for the first few years of its life. This means a double fence of 3ft sheep netting with barbed wire on top to stop stock grazing from the side or above.
Hedge quality is determined mainly by the cutting. The days of letting farm hedges grow for 12 to 15 years, and layering in rotation a small proportion each year, must surely but sadly have gone forever. This hand-layering gave a splendid variety of habitat, but far too labour intensive for modern farms where labour is in very short supply. The only feasible method today is the mechanical hedge cutter.
Many farms still trim their hedges each autumn with three passes of the cutter, one pass on each side and one along the top. This is an expensive way of getting a poor, low hedge. We now cut every 2 or preferably 3 years, with fife passes of a four foot cutter and a six inch overlap. This eventually gives us a 3ft wide hedge at the top with 7ft sloping sides.
The transition from small to big hedge takes several years, and still needs annual cutting. New hedges are usually laid after 7 to 10 years, and then trimmed annually until they reach full size. Small hedges are allowed to grow only 6 to 9 inches each year to ensure thick dense growth and avoid long spindly shoots which do not bush out properly. The final big hedge looks magnificent and is covered with blossom in Spring and berries in Autumn. We find this is true even in the year after cutting since blossom and berries are borne on older wood, much of which is left on large hedges.
Timing of cut is important. To retain all nuts and berries for wildlife, it should be as late in winter as possible. Hedges that run beside roads, tracks, pasture or leys can usually be left until then. Hedges that enclose next year’s crops may have to be cut in autumn before sowing, but co-ordinating crop rotation with cutting programme reduces their number to a minimum.
There can be exceptions to the general principle of winter cutting. For example the Brown Hairstreak lays its eggs on blackthorn shoots from mid-August to September, and the young caterpillars do not hatch out till the spring. If one is lucky enough to have this scarce butterfly then the hedge in which it breeds need cutting by early August. The general principles of conservation quite often need adapting to the particular requirements of a single species.
The hedge is of course valuable habitat in its own right. Hedgerow trees improve it by attracting a greater range of birds and insect. Apparently the variety of birds breeding in a hedge is doubled when trees provide song perches for those species that require them.
Our commonest hedgerow tree was the elm, and we lost them all to Dutch elm disease in the Seventies. Sucker elm is now regenerating, and we select and prune some of these as well as wild saplings of ash, oak and field maple wherever they occur. We plant others in suitable gaps, but find survival rate is poor. Stock grazing, root competition and summer drought lead to considerable losses and slow growth. The same is true of shrubs, particularly holly. Much to our surprise, the latter turns out to be favoured winter food for rabbits, voles and mice. Rabbits will gnaw through plastic mesh guards to get at it, and voles and mice will slip through wire mesh to strip off every leaf and bit of bark.
Hedgerow trees are not all gain. They interfere with cutting and we find hawthorn eventually dies out under trees, leaving gaps which must be fenced or planted with holly. They also provide lockout posts for pests. Woodpigeon assemble in them before feeding on the crop, and carrion crows and magpies use them to spot nests which they rob. The shading effect on crops can be reduced by keeping them mainly in the hedges running either North/South or along the South side of roads and tracks.
The value of a hedge, both as corridor and habitat, is much enhanced by developing its verges. Spraying into hedge bottoms is a waste of time and money. The resulting bare soil encourages germination of pernicious annual weeds like cleaver and sterile brome, which have thrived under this treatment. If instead a dense growth of perennial grass is encouraged, these will help suppress tha annual weeds and encourage insects, small rodents and nesting game birds. A narrow strip 2-3 feet wide beside the hedge is enough. This can be estimated by leaving it uncultivated when ploughing up temporary grass leys, but we prefer to sow a mixture of perennial wild grasses and wild flowers where possible.
The game conservation also recommends that the outside six meter strip of the arable crop should get much less spraying, with limited herbicides and no pesticides. Small weeds then develop under the corn and support a wide range of insects, which provide essential food for young gambling chicks. Other wildlife benefits too, and butterflies and hoverflies become noticeably more numerous.
A recent development of these ideas is narrow wildlife strips along the edges of arable fields. In fact the seed is 80% perennial grasses and only 20% wildflowers. Half the wild flower seeds are the annual weeds of cornfields to give ground cover and a fine display in the first year, the other half are the perennials typical of old meadows. These and the perennial grasses take over in subsequent years to give in effect a narrow strip of rich meadow.
Apart from their obvious conservation value, these wildflower strips claim to offer two agricultural advantages. They prevent the spread of annual weeds and couch grass from the hedge into the crop, and encourage the natural control of aphids by hoverflies. Hoverfly larvae are the best natural predators of aphids, since hoverflies lay their eggs earlier and at a much lower aphid density than ladybirds do. The wildflowers provide both nectar for the adults and the pollen feed which the female needs to mature her eggs. The seed is expensive, and these strips have to be specially sown. They seem to give us effective natural control of aphids, so are well worth the trouble.
The other component of the field margin is the ditch. Ditches that serve a useful drainage purpose provide damp habitat and are no problem, but many ditches have become superfluous as a result of modern practice. Victoria field drains ran right into the ditch every 30 yards or so. Now the laterals flow into a header drain which often runs parallel to the ditch and only enters it at its lowest point. Such ditches dry out completely in summer, and in recent years have stayed dry all winter too. We have tried damming one or two of them at intervals in the hope of producing at least some damp spots, but in recent years even this has had little effect.
Our new hedges still have to mature, but the effect on the landscape and wildlife is already significant. We believe that good hedges are cheaper to maintain than poor ones, and that treating field margins sympathetically has real agricultural and sporting advantages as well as wildlife benefits. Though fields will inevitably get bigger the quantity of hedgerow is much less important than the quality and pattern of what remains. So long as bigger fields are bordered by good hedges and verges connecting other habitats, wildlife on the farm will continue to flourish.