Clearing scrub and undergrowth is frequently necessary in woodlands for the reasons given here. Clearance of scrub which is encroaching on grassland, heathland and wetland habitats is also often necessary.

For voluntary groups, the most effective way of clearance is to have one or more trained chainsaw or brushcutter operators, together with others working with hand tools. The cut material can be disposed of by burning or chipping. Some material can be re-used for dead hedging, firewood or other uses, although depending on the species involved, the material may be too spiny or branching to be of value. Where chainsaws or chipping machines are being used (by trained and competent operators only), they must be used at a safe distance from, or at a different time from, the rest of the voluntary work.

In amenity woods or those where public access is being encouraged, the balance between retaining undergrowth and shrubby woodland edges for wildlife value, and the public preference for more open woods may need to swing in favour of clearance. Many potential users have a fear of woodlands and of unsocial behaviour that dense undergrowth may harbour, especially in urban fringe areas. Retain undergrowth in the more inaccessible areas, or use it as a means of blocking access to particular features you want to protect. Clear undergrowth around car-parks, along main tracks and paths or wherever you want to encourage people into the wood. Children love to play and make dens in dense growth, particularly rhododendron and laurel, so retaining some bushes near picnic sites and play areas may prove popular. For further information on public use of woodlands see Chapter 13 – Access and recreation.

Any clearance work should be done in winter. Working in late winter and spring will disturb nesting birds, and working in late summer and autumn may destroy useful food supplies of fruits and seeds. Make the most of any dry spells in winter, to avoid damage to the ground.

Procedures

Cutting by hand

Use the basic felling techniques described here. Cut as low as possible to the ground, unless you plan to winch the stumps out (see below), in which case leave a stump at least 1m (3’) high.

The nature of undergrowth and scrub means that there is a lot of branching growth to get rid of. The main requirement is to organise the group effectively so that work progresses efficiently, with the minimum handling of material. Re-use as much material as possible, and consider the use of a chipper, with trained operator, to chip the smaller branches and twigs. Otherwise, fires will be necessary.

Most species will regrow from the stump, and it will be necessary to either remove the stump, treat it with herbicide, or treat the regrowth.

Stump removal by hand

  • The basic technique is to cut around the stump and loosen the side roots which anchor it. Destroying the stump itself by hand is not feasible.
  • Use a grubbing mattock on large shrubs and saplings. The grubbing mattock has a short axe blade to sever the roots, and a longer mattock blade to lever them up. Cut all around the base with the mattock and lever the stump out with a crowbar. Don’t use the mattock for levering, as the handle may break. Difficult stumps may require several people working together.

Using a winch

  • To winch out stumps, use a winch with a cable that hooks to chain about 2m (7’) long. The chain should have small links for flexibility, and have a large eye at each end, of unequal size so that one fits through the other. Loop the chain around the stump, and then pull it tight and hook it to the winch cable. Both cable and chain must have safe working loads as great as the winch’s hauling capacity.
  • The hand winch must be securely mounted to a fixed standfast, such as the base of a stout tree. Place pickets around the tree to protect it from damage. A tractor-mounted winch, necessary for really big stumps, usually has its own holdfast in the form of a metal bar that is lowered until it digs into the ground.
  • It is often best to winch one way and then the opposite to break the anchor roots. Don’t work around the stump while the winch cable is under tension, as it may give suddenly.
  • One problem with removing stumps is that you still have to get rid of them. Stumps are heavy and awkward to lift, and damage the ground if you drag them. They also take a long time to burn. Piling them up is not usually an option as they will take years to rot down, and look extremely unsightly. Smaller stumps, which can be moved fairly easily, are best burnt. Large stumps may have to be left where they are pulled out, or moved far enough to be out of the way of access or other use. Stump grinding or herbicide treatment may need to be considered as alternatives.
  • The holes from which stumps are removed can also be a problem. In peaty soil the craters gradually fill with soft peat and become masked by a mat of vegetation, presenting a hazard to man and animal. Where holes are likely to be a hazard, they should be refilled with soil or other material from nearby. Where clearance is for grassland re-creation, harrowing will help smooth out the ground and prepare it for restoration.

Herbicide treatment

Cut stumps can be killed in situ using herbicide. This is labour intensive, and leaves the stump where it may present a hazard. On the other hand, it avoids the ground disturbance caused by stump removal, and the problem of disposing of the stump.

Cut stumps can be killed in situ using a stump and brushwood herbicide.

Clearance by machine

Various machines can be used to clear scrub, undergrowth and stumps, from tracked excavators to smaller hand-held machines. Machines which destroy stumps in situ have the advantage of avoiding the need for disposal of the stump, or for filling in the hole. A portable stump grinder adapted from a chainsaw is available, as is a specially adapted chainsaw which allows the cutting of roots below ground level. These portable machines are useful on sites with difficult access. Stony ground may prevent their use. A stump-lifting machine, as used in tree nurseries for lifting stock can be used in some situations.

Regrowth can be destroyed with an agricultural flail machine, which if repeated for a couple of years, will prevent regrowth of most species.

Large forestry mulching machines which mulch all top growth and grind the stumps are available. Although machines have the disadvantage that they may damage the ground, this is mitigated by the fact that they also have the ability to backfill holes, level the ground and prepare it for future use. ‘Creative disturbance’ can also provide good conditions for regeneration of natural vegetation. See also details below for rhododendron clearance. Machines must only be used by trained and competent operators. For further details see Practical Solutions Handbook (English Nature, 2001).

Rhododendron

Rhododendron is an introduced species which can spread rapidly on acid soils, particularly in the wetter western areas of England. It spreads mainly by seed, though also by stems which root where they touch the ground, and coppices vigorously. Its thick, dense, evergreen foliage shades out virtually all other species, and fallen leaves rot slowly, leaving a thick, acid layer over the soil. Rhododendron itself can grow in dense shade. Seedlings grow slowly for the first few years, but can then spread very rapidly. The mature leaves have a thick waxy cuticle which makes the foliage resistant to herbicide treatments. The young foliage can be treated successfully.

Merely cutting and removing the cut material is not effective, as the stumps regrow and many seedlings will appear. A combination of cutting, stump removal and spraying of herbicide on foliage is normally needed, and action must continue for some years at each site, to deal with seedlings and regrowth.

Voluntary groups can tackle limited areas of rhododendron, but large areas will need clearance by machine as hand clearance will make little impact. A phased operation to which voluntary groups can contribute is suggested below. Qualified staff will be needed for the application of herbicide.

Clearance by hand

First as much rhododendron as possible is cut down. Rhododendron is fairly easy to cut with a bowsaw, and although care must be taken, this is a relatively risk-free operation. The multi-stemmed nature of the plant means that there is plenty of work for everyone! The work can be done at any time of year, although during the winter there may be disturbance to hibernating reptiles on heathland sites, especially in smaller rhododendron clumps or along the edges of large blocks. Rhododendron also provides shelter and winter roosts for many species of birds, although the amount of growth on most sites means there is usually plenty of alternative cover.

Stumps should be removed using mattocks. Large stumps which cannot easily be removed by hand are left, and the regrowth is treated the following year. Treating the cut stumps with herbicide is not usually practical, because of the number of stumps, and spraying regrowth is more effective. The cut material can be burnt immediately, or stacked to dry for later burning. Rhododendron makes good firewood and very good charcoal, although the time taken to prepare the material for the kiln compared to other species may mean it’s not economic for commercial charcoal burning.

One year after the initial clearance, in early summer, a return visit is made to hand-pull seedlings and minor regrowth from roots. The regrowth on the stumps is sprayed with a herbicide, as are any small bushes which are too big to hand pull. Glyphosate mixed with a wetting agent is effective. Follow the manufacturer’s instructions on dilution and application, and only spray in very calm conditions. For further details see The Use of Herbicides in the Forest (Forestry Commission, 1995).

Any remaining cut material from the previous year is burnt.

Each year another check is made for seedlings, which are removed by hand. Any regrowth which has been missed or not responded to treatment is resprayed. Bushes larger than about 2m (6’) diameter by 1.5m (5’) high will have to be cut down, and either the stumps removed or the regrowth sprayed the following year.

On large areas, a Geographic Information System (GIS) programme should be used to record and map all rhododendron clumps and scattered bushes, so that treatment can be planned effectively and progress monitored. For further details see Enact (Vol 7 No 4, 1999).

Clearance by machine

Large areas of rhododendron can only be effectively tackled by machine. A 13-tonne tracked excavator can clear dense growth by uprooting the entire bush with most of the roots. A wheeled machine, such as a JCB, is not normally powerful enough, and causes significant ground damage. A chainsaw operator is also needed for the clear-up operation, along with workers to burn the debris. Seedlings and regrowth from broken roots are sprayed with herbicide the following year.

To avoid the time required for burning, as well as its environmental disadvantages, a chipper can be used to process all the cut material into chippings, which can be used for surfacing, mulch and other uses. For large areas, there are the options to use more complex machinery. A forestry mulching machine can chop up standing bushes, leaving the material to rot down. See Enact (Vol 7 No 4, 1999) for further details. A brash-baling machine can gather and bale brushwood into bundles, each weighing up to 0.75 tonne, for use as fuel in wood-burning power-generation plants. See Enact (Vol 9 No 1, 2001) for further details. For heathland restoration, the ground disturbance caused by such machines is an advantage, allowing more rapid colonisation by heathland plants.

Japanese knotweed

Although mainly a weed of stream sides, railway embankments and other ‘corridors’ along which it can spread, Japanese knotweed can cause problems in woodlands, especially along boundaries with corridor habitats. Japanese knotweed spreads vegetatively by its stems and rhizomes, which can extend for up to 7m (23’) underground from the clump. A tiny piece of rhizome can generate a new plant. Japanese knotweed grows 2-3m (6-10’) high in a thick stand of bamboo-like stems and large leaves, excluding most other plants. It occurs in nearly all parts of Britain, being most invasive in the south and west. A less common species, giant knotweed, grows 4-5m (13-16’) tall.

Under the Wildlife and Countryside Act (1981) it is an offence to plant or otherwise cause the species to grow in the wild. Under the Environmental Protection Act 1990, Japanese knotweed is classified as ‘controlled waste’, and stems, foliage, rhizomes or contaminated soil must be disposed of only at a licensed landfill site transported in a covered vehicle by a licensed waste carrier. Contact the Environment Agency for advice.

Cutting is laborious and must be continued for several seasons, and may not be successful in controlling the plant. Never use a flail or mower, as small pieces of the plant can regrow. Instead use a sharp grass hook or slasher. Do not put the cut material through a woodchipping machine, or try to compost it. Burning on site is normally the best method of disposal. Digging out is not usually feasible, because of the spread of the rhizomes. Any soil within 7m (23’) of the clump may be contaminated.

Chemical control is the recommended control method, normally using glyphosate at a rate of 5 litres/ha, with the addition of a wetting agent, applied from May to September. Two or three applications per season may be necessary over several years for effective control. New techniques of injecting the stems are being tested, to increase effectiveness of the herbicide application and avoid damage to other plants. Herbicide must only be applied by trained and competent persons.

For further details see The Japanese Knotweed Manual (Child, L E and Wade, PM, 2000), Enact (Vol 9 No 2, 2001) and visit Prevent Japanese knotweed from spreading.

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