The garden terrorist – Japanese knotweed

Japanese knotweed - the garden terrorist

Why mortgage lenders are scared of this alien invader.

If there’s a plant with an image problem, it’s Japanese knotweed. The trouble is, its reputation as a garden terrorist is well deserved. Growing up to 10cm a day and reaching a height of 3m, it forms a dense canopy that starves other plants of light so once established it can quickly take over a garden. In autumn, the decomposing leaves form an impenetrable mulch and stop anything else from germinating. What’s more, if left unchecked it will send shoots through walls, floors, Tarmac and drainage pipes causing major damage.

In 2011 a newly built house in Hertfordshire lost more than £250,000 in value when knotweed shoots were discovered growing up through the skirting boards. More recently a whole street in Coventry was served with a Community Protection Notice with potential fines of £2,500 for failing to control the plant. It’s no wonder mortgage lenders are nervous when this brute is found growing in the garden.

If you are buying a property and Japanese knotweed is discovered, what should you do? Will you be able to get a mortgage? And what if you are selling a property with an infestation in the garden?

Each mortgage lender has their own rules and some are more stringent than others. Unfortunately, all of them come at a cost, whether it’s an initial survey to assess the problem or a full eradication programme. It will depend on the extent of the problem and the distance from the building.

Nationwide, for example, asks for an insurance backed 5 year warranty against the reappearance of the plant if it’s found within 7 metres of the property. HSBC asks for a surveyor’s report and, if treatment is required, for a 10 year guarantee. Talk to your mortgage lender and find out what your options are.

There are many specialist firms who can tackle the problem but it will be a lengthy process. Treatment normally needs to be repeated over a period of several years as the underground rhizome system is extensive and extremely tough. All waste material has to be burned to prevent it re-germinating as even a fingernail-sized piece of waste matter can re-grow. Another characteristic that makes it so hard to eliminate is the plant’s ability to lie dormant – for as long as 20 years! However, even if it’s difficult to destroy completely, it can be controlled and kept within manageable bounds.

So it’s definitely not good news to hear that this alien invader has taken hold at a property you’re buying or selling. But it’s not the end of the world either.



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