Japanese Knotweed

Japanese knotweed is an invasive non native plant and was introduced to the UK from Japan in 1825.

The plant is not unattractive but its rapid annual growth and relentless spread, allows it to easily overwhelm other plants and destabilise buildings and structures.

Japanese knotweed begins to grow in early spring and can grow in any type of soil, no matter how poor. It can grow as much as 20 centimetres per day, and can reach a height of 1.5 metres by May and 3 metres by June.

It does not produce seeds, but instead spreads through rhizome (underground root-like stem) fragments and cut stems.

Japanese Knotweed produces fleshy red tinged shoots when it first breaks through the ground. It has large, heart or spade-shaped green leaves.

The leaves are arranged in a zig-zag pattern along the stem. The stem is hollow, like bamboo.

Japanese Knotweed can form dense clumps that can be several metres deep.

It produces clusters of cream flowers towards the end of July and dies back between September and November, leaving brown stems.

Find guidance from Defra (Department for Environment, Food and Rural Affairs) about your legal responsibility to deal with Japanese knotweed, other invasive plants and how to remove and dispose of them.

It is not an offence to have Japanese Knotweed on your land, but it is an offence under the Wildlife and Countryside Act, 1981 to allow the spread or not control Japanese Knotweed.

While we can act in certain circumstances, there's no statutory duty to deal with Japanese Knotweed on private land. The large investment of time and resources means it will not normally be the case that we will intervene legally.

It is not a notifiable weed under Weeds Act 1959, so there is no need to inform us.

Japanese Knotweed is a controlled waste and must go through a licenced waste carrier to an authorised landfill. Do not compost, mow or put Japanese Knotweed into garden bins. 

It is likely to require specialist treatment and typically, such treatment can take up to 3 years to make it dormant.

We cannot give legal advice to members of the public, but we would recommend you seek independent legal advice from solicitors if a neighbour is allowing Japanese Knotweed to spread onto your property.

The Anti Social Behaviour Crime and Policing Act 2014 introduced powers for us to choose to take action in relation to Japanese Knotweed. Under these provisions, there is no statutory duty where we must take action.

This is also the case under the Infrastructure Act 2015, Japanese Knotweed is a complex issue and we recommend that it should be managed by specialists. Get specialist advice about managing and getting rid of Japanese Knotweed. 

You should take legal advice about what your rights are in relation to the Japanese Knotweed spreading. Mediation may be helpful where the issue is not resolved and a possible first step to private or civil action.

If you find Japanese Knotweed on council land, please let our City Parks team know. You can send an email to cityparks@brighton-hove.gov.uk.

• stop invasive non-native plants from spreading - GOV.UK
• field studies for the biological control of Japanese Knotweed - Centre for Agriculture and Bioscience International
• general information about Japanese Knotweed - Royal Horticultural Society