Japanese Knotweed

Japanese Knotweed is a non native invasive species, it is listed on schedule 9 of the Wildlife and Countryside Act 1981. It is probably the most well known of all the INNS and has previously resulted in difficulties in obtaining finance on properties and caused the devaluation of land where it is present.

It has been reported that Japanese Knotweed can break through solid structures such as concrete. This is not true however it can exploit weaknesses in concrete such as cracks and can cause structural issues for less robust structures such as garden walls.

Japanese Knotweed has a serious affect on the amenity value of land as it restricts the use of the land and the species that will be present on the land.

The plant typically grows up to 2-3 meters in height, and is a perennial. Japanese Knotweed is spread only by the rhizome in the UK, however it only needs to have a small amount (about 1 cm) to become established in an area. The rhizome can spread to a depth of around 2 meters and laterally to around 7 metres however the lateral spread is often much less.

When disturbed the rhizome will become more vigorous and is more likely to spread, this could be from digging or from cutting the stems close to the rhizome e.g. by mowing a lawn where Japanese Knotweed is present.

The plant outcompetes all other species and the stems can impede water flow during times of flood. When the plant dies back in winter this leaves areas of ground bare of vegetation making them susceptible to erosion and landslips which can enter the river system causing silting issues further downstream.

Japanese Knotweed thrives on being disturbed so we strongly advise you not to disturb the soil around the pant. Bearing in mind that the rhizomes (roots) can spread for many metres and it can regrow from the smallest fragments.

Japanese Knotweed can be treated by a number of methods such as spraying or stem injection, however off the shelf products available at garden centres and DIY stores are just not up to the job and can do more harm than good. Cutting Japanese Knotweed also does not work. So whilst there is nothing in theory to stop you treating Japanese Knotweed yourself we would strongly suggest that you call in the experts like Restore Environmental. We also provide a 10 year guarantee for our Japanese Knotweed treatments. It’s simple, if our treatment fails and the Japanese Knotweed returns within 10 years we will return and take care of it for you.

MarkR@Restore-Environmental.Org.UK