Japanese Knotweed

We are winning the battle with Japanese and Giant Knotweed. Most ‘stands’ across the catchment are small, with exception of some of the Lower Tweed islands. With the help of the GPS maps – surveying and control work will continue. Knotweed is controlled by stem injection or chemical spray. Please report any sightings to info@tweedforurm.org.

Three species of Knotweed are present in the Tweed catchment: Japanese Knotweed, Giant Knotweed and Himalayan Knotweed, with Giant Knotweed the most common. 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.

A Giant Knotweed plant
Stem injection treatment in action