Japanese Knotweed (Fallopia japonica)

Japanese Knotweed is recognised by the Environment Agency as the UK's most invasive species, as its aggressive growth causes extensive damage to buildings, foundations, and roads, resulting in costly delays to development projects. Because of the extensive damage that can be caused by Japanese Knotweed legislation has been produced to try and prevent its spread. Japanese Knotweed is listed on Section 14(2) of the Wildlife and Countryside Act 1981 which states that “if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence.” Anyone convicted of an offence may face a fine of £5,000 and/or 6 months imprisonment, or 2 years and/or an unlimited fine on indictment.

Appearance

Flowers
8cm-12cm long clusters of small green-white flowers, blooming from late summer to early autumn.

Stems
Up to 2-3m tall; Green with red or purple specks; forms dense cane like clumps.

Rhizome
The rhizome is the concentrated energy source which allows the plant to re-grow each spring and resides under-ground. Disturbance can slow the eradication process and may spread the plant. New plants can grow from a piece of rhizome the size of a finger nail

Leaves
The leaves of the mature plant are up to 12cm in length with a flattened base and pointed tip and are arranged on arching stems in a zig-zag pattern. Young shoots have curled-up red/purple or light green leaves with red/purple colouring. ‘Lush green’ when mature, healthy and in growing season. Yellowing/ browning of leaves in late autumn/early winter.

Japanese Knotweed control and treatment

Japanese Knotweed can grow up to 10cm a day and therefore a massive 2.8m per month; so selecting the right control and treatment method is essential. SES invasive species team have experience employing various site specific techniques with regards to time scales, costs and the sites ecological needs.