Weed control for the first three to four years is essential for the hedge to establish properly. Weeds compete for soil moisture and nutrients, as well as physically smothering the young plants. The cultivated strip should be kept completely free of weeds to allow the hedge to establish, and in addition check that growth to either side of the strip is not encroaching on the hedge. Tall growth to either side provides useful shelter, but check it does not collapse onto the hedge plants as the summer progresses.
Hand weeding
This may be suitable for short lengths of hedge that can be weeded frequently. Pull up any weeds you see, to maintain the original planting strip bare of all growth other than the hedge. Deep rooted weeds such as dandelions, dock, burdock, bindweed and others should be carefully dug out, trying to disturb the hedge roots as little as possible. Using a herbicide to spot treat is likely to be less damaging to the hedge plants.
Mulching
A mulch is a layer of material laid over the surface of the ground to suppress weed growth and retain soil moisture by reducing evaporation. Many materials can be used for mulching, including garden compost, manure, composted bark or chippings. Plastic sheet mulches are available in rolls, designed for use with hedging. Waste materials such as newspaper, cardboard, carpet or plastic sheeting can also be used. The mulch should entirely cover the surface of the cultivated strip.
Organic mulches
These include compost, composted bark, chippings or leaves, straw and manure. Organic mulch should have been composted at high temperatures to kill off any roots or weed seeds, or the mulch itself will be a source of weed growth. Fresh bark contains volatile oils which may be toxic to young trees, so should also be composted before use on hedging. The mulch should be spread in a layer at least 4” (100mm) thick onto weed-free ground, immediately after planting. Vigorous weeds are able to grow through a 4” mulch.
Try and plan ahead by providing mulch from nearby, for example by leaving some straw bales to rot, or gathering leaves for composting, or chipping a load of prunings and composting them nearby. Any old rotten tree stumps which have to be removed when replanting an old hedge line will form an immediate source of mulch, and go some way to mitigate the loss of dead wood habitat.
Adisadvantage of organic mulch is that it provides a home for voles and other rodents, which may damage the young hedge plants by gnawing the bark. This can be a serious problem which can cause loss of the entire hedge.
Use of a herbicide which prevents germination of weed seeds under the organic mulch will give weed control over a longer period. Any weeds that do germinate in the mulch in the first year should be easy to remove, as the surface will be very friable. Some deep rooted plants may come through from beneath, and are best spot treated with herbicide. After a year or so, much of the mulch will have become incorporated into the soil, and although this is very beneficial for the hedge, its weed control effect will be reduced. Hand weeding or herbicide control may be necessary for another year or more, unless more mulch is added.
Sheet mulches
Black polythene and other sheet mulches are available in rolls for use with hedges. Sheet mulch provides good cover against weeds, although there may be some weed growth through the planting slit which can be difficult to remove. Black polythene has the advantage that it warms the soil in spring and maintains warm, moist conditions throughout the growing season, encouraging good root development. However, initially this will encourage surface rooting, so ensure the mulch is left in position for at least three years by which time roots will have gone deeper. Small rodents can be a problem under sheet mulches, and can be discouraged by laying gravel or heavy clods of earth on the sheet.
Sheet mulches may be damaged by dogs, foxes or cats scratching at it, particularly if there are rodents nesting beneath. Sheet material must also be anchored carefully so it does not get damaged by the wind. The fairly small extra cost of anchoring with gravel is likely to be worthwhile.
Sheet mulches can be laid either before or after planting, depending on the size and type of hedge plants, and the method of ground preparation. Sheet mulch can be used as an initial ‘weedkiller ’, by laying it and anchoring it over the mown hedgeline several weeks in advance of planting. This will kill off grass and annual broadleaved plants, but bramble or woody growth may penetrate. Use a 500 grade polythene, rather than a thinner material, to last for 2-3 years after planting. Sheet mulch can also be laid over prepared ground to keep it weed free and protected from erosion.
Laying sheet mulch after planting
This is preferable to laying before planting, but is only possible if plants are to be pruned to a short stump immediately after planting, or if plants are small and not very bushy. This method keeps the holes in the sheet to a minimum size, thus reducing weed growth around the stem.
The sequence of planting, followed by hard pruning and laying sheet mulch is quick and efficient, and promotes strong bushy growth in good weed-free growing conditions.
Plant the hedge as described here. Hawthorn, blackthorn, myrobalan or wild privet should be pruned hard to leave a stump of 4-6” (100-150mm), cut at an angle to easily pierce the polythene.
- Unroll a length of polythene, about 5m long, as longer lengths are difficult to handle in all but very still conditions. Anchor the end by pushing it into a slot in the ground with a spade, or by weighting it with stones or clods of earth.
- Secure along the windward side by digging the sheet into a slot as shown.
- Press the mulch sheet down over the pruned stems, so that they pierce the sheet.
- Secure the leeward side of the sheet in the same way.
An alternative method for small bushy plants is as follows:
- Temporarily anchor the end of the roll, and unroll a length of about 10 metres alongside the hedge. Do not stretch it taut, but allow it to lie fairly loosely. Anchor it temporarily with lengths of timber or similar.
- For single row planting, make a hole with a sharp stick along the centre line directly opposite each plant.
- Remove the temporary anchors, and secure the end of the roll in its correct position. Then starting at the end, thread each plant through its respective hole, by carefully gathering the branches together. Try and keep the holes as small as possible. This operation is easier with a helper, and if the plants are spaced more than 8” (200mm) apart.
- Spread out the section of sheet and anchor securely. Continue along the line.
Laying sheet mulch before planting
This method should be used for larger, bushy and thorny plants which are not being pruned after planting, and which are too big to easily thread through holes in the sheet. However, such plants should also have sturdy, spreading root systems, which should not simply be crammed into narrow slits in the ground. The soil beneath the plastic mulch must be properly prepared so that it is friable and easy for the roots to penetrate. For making the planting slot, use a narrow border spade or a junior spade, with a blade about 5” (125mm) across, in order to keep the slit in the polythene as small as possible.
- Lay the sheet mulch and anchor securely into a slot all round.
- Use a knife to make a slit across the mulch, the width of the spade, at each planting position.
- Insert the spade through each slit, using a rocking motion to enlarge the slot in the ground without tearing the polythene, and position the plant with a sideways ‘wiping’ motion.
Various gauges of polythene are available, including 200, 250 and 500, as well as thicker ‘landscape fabrics’ and other sheet materials. Check with the supplier which material will best suit your purpose. Black polythene can be covered with a thin layer of gravel to weight it down and discourage burrowing rodents. For a single row hedge, allow 1 tonne (0.6 cubic metres) per 100m length of sheet.
Costs will vary with individual specifications, but you are likely to spend half as much again on sheet mulch and gravel, as on the plants. Fitting the mulch and spreading the gravel will also take longer than the planting operation. However, this is normally money and time well spent, as a properly fitted sheet mulch will do away with nearly all weeding for the first 3-4 years, and ensure the hedge successfully establishes.
Cheap waste materials can also be used as available, including thick plastic sacks, layers of newspaper or cardboard. Check that nothing toxic is being introduced onto the site, and be prepared for weed growth between the edges of overlapping materials.
Herbicides
Herbicides can be effective both in clearing vegetation before planting, and in controlling weeds after planting. Herbicides should be used carefully in accordance with manufacturer’s instructions. Most herbicides are only available to persons qualified in their use, but there is a small range of herbicides suitable for amateur use which are available from garden centres and agricultural suppliers.
Two widely used herbicides are described below.
Propyzamide is available to amateurs in the form of ‘Kerb granules’, which are applied to the ground around the hedge plants immediately after planting, and suppress germination of seeds for several months. A ‘shaker pack’ sufficient for 120 plants is available, as well as larger quantities. Propyzamide can also be applied annually in early spring for two to three years after planting to keep the hedge weed free until it is established. Only apply to weed-free ground.
glyphosate is available in several formulations for amateur use. It is a translocated, non-residual herbicide which is applied to the foliage, where it is absorbed and translocated to kill both leaves and roots. It can be used as an overall spray to kill rough or mown grass or other perennials prior to planting. It should be applied at least a week before planting, to allow time for the herbicide to act. On good soils, the hedge plants can be planted through the dead vegetation, which will act as a mulch. Alternatively, the dead vegetation can be dug in before planting. glyphosate is effective at any time when the target plants are actively growing. After planting, glyphosate can be used to keep hedges weed-free until established, but care must be taken that spray is not applied to the hedge foliage. Only spray in still conditions.
Even where herbicides are used, some hand weeding may be needed. Beware of deep rooted scrambling plants, particularly bindweed, hop and bramble, which can quickly regrow and smother young hedge plants. Annuals may germinate at almost any time that conditions are suitable. For example, cleavers can germinate in autumn, remaining small throughout the winter, and then quickly grow in spring to smother young hedge plants with its clinging, sticky growth. Nettles are not so much of a problem, as their growth is fairly sparse, and rain can penetrate through. Any thick growth of grasses should be dealt with, as grass competes strongly for moisture and nutrients.
Try not to use herbicides for more than two or three years, as with repeated herbicide use, the tendency is for resistant and troublesome weeds such as cleavers, bindweed, creeping thistle and others to become a problem. At the same time, herbicide use delays the establishment of a more benign hedge-bottom flora, which might include species such as lady’s bedstraw, ground ivy, speedwell and hedge garlic on dry hedgebanks, and ferns, cuckoo- pint, herb Robert and campion on damp, shady banks. As the hedge matures, it can provide support for scrambling plants such as bryony, honeysuckle, hedge bedstraw and vetch, without the hedge itself becoming smothered. For further details on hedgerow flora see page 16.
The treatment of the ground to either side of the hedge is significant in affecting the development of the hedge flora. Adjacent to grassland, or where a mown grass margin is maintained, a benign flora is more likely to develop. The vicious circle of weed species and herbicide use is more likely to develop where the adjacent land is arable. See here for information on field margins.
Hedge weeds
Weeds are simply plants in the wrong place, that succeed at the expense of other species which are deemed more valuable. In the stockproof hedge, the main aim is to establish a close-spaced row of sturdy shrubs, and other woody species and climbers are not welcome. Elder is the main problem shrub, and should be dug out as soon as it is noticed. Climbers are characteristic hedge plants, needing the support of other shrubs, and withstanding regular trimming, but nevertheless they should not be encouraged in the newly planted stockproof hedge. The species listed below should be pulled, cut out or dug out. Most will readily regrow or reseed, so the aim is to hold them in check rather than to eradicate them. These plants are more likely to be present where you are planting into gaps, or replanting near the line of an old hedge, garden or woodland. Bindweed and bramble are common in cultivated ground, the other species less so, but still common and widespread through most of the UK.
In a wildlife hedge, a more relaxed regime can be followed, as many ‘weed’ species have high wildlife value. If any of them appear, be grateful, but keep growth in check for the first few years, until the shrubs and trees are sufficiently large to support climbers without being smothered.
Bindweed (Convolvulus arvensis)
Bramble (Rubus spp)
Roses (Rosa spp)
Honeysuckle (Lonicera periclymenum)
Black bryony (Tamus communis) – poisonous
White bryony (Bryonia dioica) – poisonous
