The plant is responsible for the destruction of many native habitats and the abandonment of land through out the British Isles. The reason for this is simple. Where conditions are suitable rhododendron will out compete most native plants. It will grow to many times the height of a person and excludes all light.

Once the native plants have disappeared, the animals which rely upon them either directly or indirectly for food can not survive. Thus rhododendron woods are barren. Species such as woodland butterflies disappear. This is because the caterpillars of most woodland butterflies can only feed on the wildflowers and grasses which are found in the glades and rides of well managed woodland.

Rhododendron supports no species of animal. Dormice one of Britain's most endangered species of mammal has been severely affected by habitat loss. Some of this has been because rhododendron has taken out competed native plants and shrubs which are essential for the dormouse to survive.

Song birds which feed on either seeds or invertebrates are therefore reduced to trying to survive in reduced numbers by feeding in the tree canopy. Once the song bird populations decline so do species such as sparrowhawks which predate upon them.

Furthermore as the forest floor is barren in such woods no young trees grow to replace those which ultimately die through natural causes. Thus the rhododendron completely takes over, this is particularly noticeable in Silver Birch woodlands as this species is short lived.

Broadleaf woodlands are capable of supporting a complex and interlinked rich diversity of plant and animal life. This is because there should be four distinct layers of vegetation. These are the climax vegetation such as Oak or Ash, an understorey of species such as hazel or holly, a field layer which is typically grasses and wild flowers and finally a ground layer of mosses and lichens. Crucially each layer supports a whole range of invertebrates which in turn support the larger and larger animals which make up the food chain.

To put the value of native plants in perspective, a single willow tree can support over 400 different species of insect and mite. There may well be hundreds or even thousands of individuals of each of the species present. In woodlands dominated by rhododendron only the trees which have their canopies above the rhododendron can survive.

However it is not just woodlands which have suffered. Heathlands which have declined by 75% in just the latter half of this century, have also been seriously affected. Once again rhododendron dominates many such areas and as a consequence the heathland plants and animals have disappeared. It is hardly surprising therefore to find that rhododendron together with the other causes of habitat destruction has caused the disappearance of 150 species from Britain in 100 years. A situation which has not even occurred in key areas of world concern such as the Amazon Rain forests. Little wonder that Agenda 21 calls for world populations to "act locally and think globally".

However restoring areas which have been colonised by rhododendron is not just a matter of cutting the vegetation. The plant is notoriously difficult and expensive to actually kill. The leaves are waxy and herbicide treatment must include a chemical additive to help break this surface down. Even then where rhododendron is well established with a large root system such herbicide treatment usually has to be done over several years. This is because herbicides do not translocate well through the plant.

Techniques such as mist spraying or tractor application are usually out of the question in woodlands because of the risk to trees.

There are a variety of techniques for the mechanical removal of rhododendron. These usually employ a tractor or tracked swing shovel with a rotary flail mounted on a moving hydraulic arm. In sensitive conservation areas such techniques may well not be appropriate. Such mechanical devices often leave a thick layer of smashed rhododendron on the ground which may have to be removed using expensive manual labour.

Once rhododendron has been removed and eradicated the toxic humus layer still remains. Where this has built up over a number of years the resulting thick mat prevents natural regeneration. The only solution is to remove the layer. This often can not be done by mechanical means and thus may require several hand operations to effect conditions which favour regeneration. However even then reinfestation can easily occur from the millions of seeds which will have been produced over the years. Thus areas where rhododendron has been present require careful monitoring over a number of years. Prompt action must be taken at a relatively early stage to prevent effective re-establishment.

Further problems exist because any serious infestation is likely to affect neighbouring areas which may not be in the same ownership. Unless these areas are cleared the seeds as well as the limbs of the plant will encroach. Given time a single plant can cover 100 metres² and grow to more than 10 metres high. This should be taken into account when making out a management plan. Each site is different but where there has been a significant presence of this plant and where it is present in adjacent areas, it is prudent to budget for a reinfestation figure of 15% per year.