How to deal effectively with Japanese Knotweed

Our gardens are full of exotic shrubs bought back by Victorian plant hunters, most of which bring us colour and enjoyment.  However, there is one notorious for blighting, not only gardens but also causing structural damage to buildings.  Japanese Knotweed was transported to England from Japan in the 19th Century and,  at the time was highly prized as an ornamental shrub.  Little was known about its destructive potential when removed from its natural habitat or away from the pests that control its spread.

The presence of Knotweed, has caused problems when it comes to buying or selling houses.  Mortgage companies have been unwilling to lend money to buy houses which could be destroyed by the roots finding their way through masonry or concrete.  As buyers can’t get a mortgage this reduces the value or may prevent the sale the house. If you suspect you have knotweed, don’t attempt to treat yourself, as shop bought chemicals just won’t do the job and digging it up may leave tiny fragments which can sprout and cause outbreaks in other areas. 

Recently, the Property Care Association (PCA) together with the Royal Institute of Chartered Surveyors (RICS), has put together guidance to help deal with Japanese Knotweed.  The Council of Mortgage Lenders (CML) has also endorsed this scheme and, according to their website treats each property on a ‘case-by-case basis’  looking for evidence of initial and ongoing treatment.  

The best thing you can do is get it treated early, using only a specialist weed control contractor who is licensed to use more potent chemicals. Even then, treatment can take 3-4 years to ensure it is killed off properly.  Make sure you look for contractors who can provide guarantees that are backed by UK Insurance Companies which can show your mortgage lender that the treatment has been done properly or is in progress.  Sellers can then provide an insurance backed guarantee (IBG) which means their house is safe to buy.  Buyers can also get a mortgage and have peace of mind that their dream home is one that is safely weed-free.

So, although Japanese Knotweed is the last thing you want to find in your garden, there is lots of information on the web such as here to help you identify the shrub and Hus’s Peter Madsen would be happy to advise you further.