Japanese Knotweed (Fallopia japonica) is the UK’s most invasive non-native plant, and was brought into the country by our horticultural ancestors in the 1900s.
As its name suggests it originates from Japan, having evolved on the sides of volcanoes. It grows rapidly, with new shoots appearing in spring and growing to approx. 3m high by June. It has pretty white flowers in the summer. In autumn the above-ground part of the plant dies back, leaving brittle canes left standing over the winter period. More vigorous stems will appear the following year, gradually spreading to larger areas.
All plants in the UK are female, so the seeds in the flower are not pollinated. All new outbreaks of knotweed result from fragments of viable rhizome, that may be spread within soils being moved from site to site, by fly-tipping, by natural processes such as river bank erosion, or by animal movement.
There are hybrid varieties of Japanese knotweed, notably Giant knotweed, which has larger leaves and generally taller plants, and Dwarf Knotweed. These are said to be not as invasive as Japanese Knotweed but has the same legal status and treatment methods.
Japanese Knotweed has come under the spotlight since a legal ruling in the UK High Court in 2018 where the Defendant (Network Rail) was found guilty of Trespass allowing Japanese Knotweed to spread from their land on to a homeowner’s land and causing a reduction in the property price. Network Rail were ordered to pay compensation to the homeowner to cover the devaluation in the property value and additionally pay for a recommended treatment plan with an Insurance Backed Guarantee.
Since this case was successful, many homeowners who find they have Japanese Knotweed on their land which has come from a commercial type property such as Network Rail, Council Land or Property, Housing Association, Commercial entities like Industrial Estates, Shopping Complexes and the likes, now have a route of claim to protect their property value and recover compensation and treatment costs.
If you are unsure of your rights the Japanese Knotweed Agency can help you.