Japanese Knotweed – what’s the problem?


Author: Ben Milloy


Japanese knotweed was originally imported from Japan as an ornamental plant, admired for its attractive white flowers. The plant’s aesthetic qualities, however, have long been overshadowed by its reputation as an invasive and destructive species, which can outmuscle other vegetation and cause serious structural damage to buildings.

In view of its possible impact on a property’s market value, as well as potentially expensive and protracted remedial works (its eradication from the 2012 Olympic site in Stratford is thought to have cost £70 million), it pays to address any knotweed growing on your land at the earliest opportunity. But what can you do if the problem is posed by knotweed growing on a neighbour’s property?

There is no law against having Japanese knotweed on private property. While section 14 of the Wildlife and Countryside Act 1981 prohibits planting or otherwise "causing" knotweed to grow "in the wild", government guidance suggests that "the wild" would not include private land. Where the threat is from neighbouring land, therefore, a concerned landowner’s best option is in civil law; specifically the law of private nuisance.

A private nuisance is commonly described as an unlawful interference with a person’s use or enjoyment of land, or some right over or connection with it. It is widely accepted that nuisance can arise in three ways:

  • encroachment on a neighbour’s land;
  • direct physical injury to the land; or
  • interference with the enjoyment of the land.

Where a court establishes that a nuisance exists, or is likely to, the available remedies include damages (reflecting the loss in value or amenity value of the land) or an injunction. In very limited circumstances, a victim may be entitled, without prior permission from the court, to take action to abate the nuisance themselves.

The prospect of a private nuisance action for encroachment or damage caused by invasive weeds is a (relatively) recent development. Following an 1890 case (concerning the spread of thistles) it became established law that no duty was owed to an adjoining landowner in respect of something occurring naturally on an individual’s land. A change of approach came in 1990, however, in a case involving troublesome soil and detritus falling downhill from one landowner’s property onto another. This time, the Court of Appeal held that where an individual has on their land a naturally occurring hazard which poses a threat to neighbours, there was a duty to do what was reasonable in the circumstances to remove or reduce the hazard.

In line with private nuisance case law generally, the question of whether reasonable steps have been taken by the offending landowner will most likely depend on a range of factors, including the scale of damage likely to ensue, as well as the cost and practicality of preventing its spread. While specific judicial guidance on the extent to which a landowner must prevent the spread of an invasive plant like Japanese knotweed is scarce, the following are common sense steps that a threatened landowner should take:

  • Make sure you, or your agents, are familiar with Japanese knotweed (a recently reported survey suggested that fewer than half of gardeners could correctly identify the plant).
  • Keep an eye on what is growing on surrounding properties, particularly along boundaries (knotweed can encroach both above and below ground).
  • Where there is evidence of Japanese knotweed, raise the issue in writing with the owner of the adjoining land at the earliest opportunity. It is worth noting, however, that Japanese knotweed cuttings are classified as "contaminated waste", the incorrect disposal of which is an offence. The need for precaution and/or specialist assistance should therefore be emphasised to avoid exacerbating the problem!
  • Retain copies of correspondence or notes of discussions – they may be useful in the future.

Hopefully such an approach will result in an early and inexpensive resolution. If not, consult your legal adviser as soon as possible. The consequences of failing to do so can be drastic: the presence of Japanese knotweed revealed on inspection can lead to the property becoming unsaleable or unmortgageable.

Ben Milloy, Trainee Solicitor, Fladgate LLP (bmilloy@fladgate.com)

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