Japanese knotweed (Fallopia japonica) was introduced from the far East to the UK in the 19th century as an ornamental garden plant. It tends to grow on disturbed ground on riverbanks, railways, roadsides, waste land and in urban areas; and is occasionally found in woodland habitat. It can be recognised by its bamboo-like stems, with purple speckles and heart shaped leaves positioned in a zig-zag, twig pattern. It has an extensive root system of rhizomes, growing up to 3 m deep and potentially extending up to 7 m laterally.
Help us control this damaging invasive non-native plant species by sending in your sightings. If you think you’ve seen Japanese knotweed or need more information, please email us on info@tweedforum.org giving your name, contact number, the exact location of the plant and the date seen. Please include a photo of the plant if possible.
Impacts
Japanese knotweed is capable of exceptional growth rates. In spring and summer, the bamboo-like shoots grow very tall, forming dense ‘stands’. Along riparian zones, Japanese knotweed blocks access to the river, quickly out-competes native plants and undermines riverbanks. In recent years, there has been a rise in properties being affected by Japanese knotweed, which has led to problems securing mortgages.
Controlling Japanese knotweed
3 species of knotweed are present in the Tweed catchment: Japanese knotweed, giant knotweed and Himalayan knotweed and we control all 3 species using the same method. Stem injection is a very successful, albeit time consuming, method of treating knotweed species. Chemical (2 ml of 50/50 glyphosate/water) is injected into each hollow stem, using a specialised stem injector. The best time to target this plant species is at the end of the growing season, when the plant “draws back” for the winter (August–September). In some cases, when the stand of knotweed is particularly large, it will be sprayed using a knapsack and then injected on the return visit. This is to save time; spraying is effective, but the odd stem nearly always gets missed. Treating knotweed is a matter of patience and persistence as it can take several years to eradicate at a given site.
Volunteer
Why not volunteer with us? You can access training, equipment and advice through the Tweed Invasives Project. To find out more contact us at info@tweedforum.org.