Determined weeds are every gardener and landscaper’s worst nightmare. Japanese knotweed is no exception. This problematic weed is not only extremely difficult to remove permanently, but also has a lot of legal and financial issues if an infestation occurs on a commercial property or development site.

Japanese knotweed (Fallopia Japonica) is an extremely fast-growing perennial. The weed has tall, dense stems (often likened to bamboo) which can grow up to 7ft tall. In the winter the plant dies back down to ground level, but by spring, fresh shoots will appear from pink buds. The plant forms thick clumps with purple flecks on the stems and heart or shovel shaped leaves.

Fortunately, Japanese knotweed is a non-native species to the UK and does not occur very commonly. Brought to the UK for its beauty in the early nineteenth century, the weed can also sprout from small sections of rhizomes, underground horizontal stems that grow continuously.

Although reasonably rare, knotweed can be a real problem if it does occur. It also spreads very easily, particularly during construction, soil transportation, and on footwear. Left untreated, it can spread rapidly and drastically impact property value. To help avoid any knotweed nightmares, we’ve compiled the five best ways you can either remove or control Japanese knotweed.

Glyphosate based Herbicides

These herbicides are particularly effective at killing Japanese knotweed either through spraying onto the foliage or injecting into the stem. To get rid of knotweed completely, you must be persistent and therefore the plant must be treated through all stages of growth throughout the year. Like with all herbicides, proximity to water and the general public must be taken into consideration if this method is used.

Clearing and Chipping Stems

As the stems are so thick and strong, cutting down and clearing is a vital part of gaining access to and controlling the knotweed plant. If the stems are to be chipped, it is vital to make sure they are thoroughly dried to prevent spread and regrowth. This is best done in winter once the stems have been killed and dried. 

Psyllid Insect Control

Although not a means of eradicating Japanese knotweed, the psyllid insect, also known as jumping house lice, are very effective at keeping the plant under control and preventing spread. This method is natural and beneficial for the environment, with DEFRA beginning a release programme of psyllids in Spring 2010.

MeshTech

An environmentally friendly and effective method for controlling the spread of Japanese knotweed, MeshTech was designed by Dr Eric Connelly and JKSL. Simple yet effective, and without the need for chemicals, the fine mesh laid on the ground simply ensures the stems are either prevented or disrupted when trying to grow upwards. This method ensures no harm to the rest of the environment.

Disposing of Rhizomes

Just the smallest section of a rhizome can allow a knotweed to sprout. Fully excavating the rhizome network using heavy plant machinery will ensure the soil is clean, and one of the best ways of getting rid of the knotweed.