The Peril Of Japanese Knotweed

In over twenty years of assisting landlords I did not think there was anything new that could be sprung upon me, but as happens occasionally, I was wrong. Twenty years, or even ten years ago, Japanese Knotweed, was not perceived as a threat of any kind. It was, after all, introduced in the 19th Century by travellers who thought it was an attractive plant.


But over the last 5 years, this plant, having thrived and spread over large areas of the country, suddenly raised its’ decorative head after decades and has been recognised as the destructive vegetation it is, with roots up to 3 metres deep.

This is still sounding fairly innocuous; what makes this more destructive than rhododendron or Himalayan Balsam, which may be seen as a nuisance (when growing where they are not wanted) but no more than that? It is those roots which make this such a worry to home-owners; they have the strength to penetrate building foundations and cause instability, if not worse.

Despite television programmes that have featured this menace, the vast majority will not be aware of its’ presence until – they apply to re-mortgage, or to sell their property.  Then they will be told that the presence of Japanese Knotweed makes their property unmortgageable if the Knotweed is within 10 feet of the boundary, which equates to worthless, as I heard of one surveyor saying to a hapless home owner.

That sounds bad enough, but it gets worse – if Japanese knotweed spreads from your land, you could find yourself at the wrong end of a claim for damages, with prison a possible penalty if the issue is ignored. 

The good news is that it is treatable. The bad news is that it is an expensive and long process. It can only be dealt with by a licensed operator, this is not a do-it-yourself process. Footfall on the knotweed should be avoided, as it can spread very easily needing only an amount the size of a pea to create a new plant. During Autumn, it is dormant, leaving bamboo like shoots above ground. Even this, though, cannot be disposed of in the usual garden waste, so resilient is it, that it can re-grow in the following Spring, causing the same problems in other areas.

It is the risk of spreading that landlords need to be aware of. They must carefully inspect their boundaries and any plants they cannot readily identify must be investigated. Leaves are large and heart or spade shaped; in fact, the very young shoots can be roasted and eaten, according to a recent television programme, but this is not a reason to cultivate it!  Eating the top of the plant will do nothing to attack those dangerous roots. 

Whilst my initial concern was for the landlord who may find themselves at the receiving end of a claim, there is the other aspect, which is that they may find themselves in a position to claim from someone else if the Knotweed has spread from adjoining properties. Many Churches are finding that the foliage that makes such a pleasant back-drop to wedding photographs etc., however this will actually cost them a lot of money as they try to resolve the matter with concerned neighbours.

Be on your guard – I have had two emails from licensed operators warning of the dangers. Is this going to replace PPI as the next big campaign?

For advice on buy to let issues – Ask Sharon

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