Renfrewshire Council

Japanese Knotweed

Japanese Knotweed

Japanese Knotweed is a non-native plant species that was originally introduced into Britain around 1825 as an ornamental garden plant.

Japanese Knotweed has since become naturalised and is increasingly found on river banks, woodlands, grasslands, coastal areas, urban parks and private gardens. It has also been known to grow through brickwork, tarmac and concrete.  

Japanese Knotweed is not harmful to human health, but will displace plants that are naturally present and threaten biodiversity.

Japanese Knotweed identification

Japanese Knotweed is herbaceous perennial that can grow to up to 3 metres in height. 

The cane-like stems are green with reddish/purple speckles. Large green heart shaped or oval leaves zig-zag from the stem. Flowers are white sprays typically between August and October, followed by small winged fruits.

Who is responsible?

The management of Japanese Knotweed is the responsibility of the landowner/tenant.

Renfrewshire Council has no powers to enforce treatment of Japanese Knotweed and has no requirement to undertake treatment of Japanese Knotweed, other than that growing on land owned by Renfrewshire Council.

Renfrewshire Council cannot make recommendations regarding suitable Japanese Knotweed treatment contractors. However, there should be a selection of companies listed in the local business directory or online.

Japanese Knotweed legislation

You will not be prosecuted for having Japanese Knotweed growing on your land. However, it is an offence under the Wildlife and Countryside Act 1981 act to 'plant' or 'otherwise cause to grow in the wild' a number of non-native plant species, including Japanese Knotweed.

Japanese Knotweed control

Chemical herbicide is the most successful best way of getting rid of Knotweed, but it may take three years to fully eradicate the plant.

Herbicides or weed killer products that are non-persistent in the environment (containing an active ingredient such as glyphosate) are widely available from most gardening stores.

The most effective time to apply the herbicide is between July and September when the plant is in leaf.

The correct disposal of this material is important as it can easily take root and spread.