Many property owners are not aware, that having a plant known as Japanese Knotweed in their garden, not only has the ability to cause serious structural damage to their property, but is likely to make it difficult to sell, as many Building Societies and Banks criteria, is to decline to lend on properties that have Japanese Knotweed, or even if it is in an adjoining neighbour’s garden.

Japanese Knotweed is a hardy, bamboo-like perennial plant that grows quickly and strongly and spreads through its underground rhizomes, or roots and thick clumps or stands, can quickly grow to a height of over 2 meters.  It was first introduced to Britain by the Victorians, as an ornamental plant.  Its leaves are heart shaped and are carried alternatively on zig-zag stems.

There are four main reasons why Japanese Knotweed is a problem:-

  • It spreads easily via rhizomes and cut stems, or crowns.
  • It out competes native flora.
  • It is difficult and expensive to control, or eradicate.
  • It can cause structural damage to buildings.


Because of its regenerative properties and invasive habit, Japanese Knotweed is listed under the Wildlife and Countryside Act 1981, as a plant that is not to be cultivated or otherwise introduced into the wild.  The Environmental Protection Act 1990, also lists it as ‘controlled waste’, to be disposed of properly.  You have a legal obligation not to allow it to spread, if it occurs on your land.  If it crosses your boundary into adjoining land, your neighbour could take legal action against you, for civil nuisance.

The most common effects include the following:-

  • Drains and other buried services:  Knotweed roots can exploit existing cracks and gaps in the pipes, in their search for water, which will further damage and in some cases, block the drains. 
  • Patios, paths and driveways:  Japanese Knotweed can exploit poorly laid surfacing, grow between slabs and movement joints of concrete drives and disrupt brick paving, in its unstoppable quest for light. 
  • Boundary and retaining walls:  Closely packed stands, can undermine garden walls with shallow foundations.  The mass of the stands, can ‘push over’ retaining walls, often resulting in sudden collapse.
  • Outbuildings:  Vigorous stands of Japanese Knotweed, can overwhelm lightweight, insubstantial and poorly founded outbuildings, such as garden sheds, greenhouses and poorly built garages.


If you have Japanese Knotweed in your garden, do not panic.  Find out more – is the plant really Japanese Knotweed ? What can be done to control it ?  Find out the best options for your garden.  The best advice, is to consult a specialist firm of Japanese Knotweed contractors, to carry out an investigation report and to advise on the best control method, to eradicate the site, whether chemical or physical control. Ensure your chosen contractor, will provide a guarantee that can be assigned to the new owners of your property, as and when you consider selling.

Remember, you have a legal obligation not to allow it to spread and early treatment of a new colony is vital, as it can soon invade large areas and this will make it more expensive and difficult to control later.  For more information visit www.environment-agency.gov.uk.

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