The Knotty Question of Knotweed

Japanese knotweed is a fast-growing, invasive plant which, if left uncontrolled, can cause extensive damage to the built and unbuilt environment.  It is amongst the plants listed in Part II of Schedule 9 of the Wildlife and Countryside Act, 1981 (‘the schedule’) to which s14 of that Act applies i.e. a person shall be guilty of an offence if he or she plants or causes to grow wild any species listed in the schedule.  It is not a crime to have the plant within your own grounds but you will be liable if it spreads into the wild or (pursuant to the civil law) on to a neighbour’s land.  Further, disposal of the plant material may cause difficulties as it is classified as ‘controlled waste’ under the Environmental Protection Act, 1990.  It can, therefore, only be transported and disposed of at a licenced site by a licenced contractor.

The question of how damages are assessed when the plant is in danger of spreading onto a neighbour’s land came recently before the courts (Network Rail Infrastructure v Williams & Waistell [2018] EWCA (Civ) 1514).  The plant had grown on Network Rail’s land for some 50 years or more.  When it spread to within 7 metres of the neighbouring borders, the owners issued proceedings seeking an injunction against Network Rail requiring that it abate the nuisance.  They claimed mortgagees refused to lend on properties within 7 metres of the plant and therefore the value of their properties was reduced.  The Recorder at first instance refused a mandatory injunction but considered damages in lieu.  He awarded treatment and insurance costs plus £10,000 to one claimant and £10,500 to the other in respect of residual diminution in the market value of their respective properties.  However, the Court of Appeal said “The Recorder’s conclusion that the presence of knotweed on NR’s land within seven metres of the claimants’ properties, because it diminished the market value of the claimants’ respective properties, because of lender caution in such situations, was wrong in principle.”  Nevertheless, the plant and its rhizomes “can fairly be described, in the sense of the decided cases, as a “natural hazard”.  They affect the owner’s ability fully to use and enjoy the land.  They are a classic example of an interference with the amenity value of the land.”

The appeal court did not resubmit the question of damages to the lower court feeling “the cost of that exercise would be out of all proportion to the amount of damages in issue”.  In consequence, the decision of the Recorder was upheld but for different reasons to those which he gave.

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