Japanese knotweed is a very invasive plant which causes damage and competes with other plants for nutrients, water and space. Its ability to re-grow from cut stems and rhizomes means it is difficult to control. It spreads and can form dense thickets that exclude other plants and can block access to roads, rivers, railway lines and waterways. It can grow in a wide range of conditions, including low areas, along rivers and streams, on rights-of-way and around old homes and farmsteads.
The best approach to controlling Japanese knotweed is to use multiple eradication methods right from the start. It is particularly important to ensure that cutting does not stimulate new growth as this will make re-sprouting much more likely.
One of the most common ways to kill Japanese knotweed is by spraying the plants with glyphosate or triclopyr herbicide. You will need to apply this to both the growing shoots and the rhizomes. It is also essential to apply the chemical weed killer in the summer and autumn when the plant is growing at its most vigorous. It is also important to use the correct safety equipment when applying chemicals such as a face mask, gloves and long-sleeved shirt.
A number of different biological control agents are available for Japanese knotweed, including nematodes, insects and plant pathogens. These biological controls are effective at killing Japanese knotweed, but they can be slow to work and may take several years to completely eradicate a small patch. They are often used in combination with other control methods, for example, grubbing with a pulaski tool, cutting or herbicide treatments.
Using a chemical treatment for Japanese knotweed can be effective, but it is very important to choose a high-quality product and follow the instructions carefully. In particular, a good quality glyphosate concentrate will have less of an impact on non-target species than a cheaper, lower-quality product. It is also vital to be aware that Japanese knotweed rhizomes can remain dormant in the soil for many years, meaning that even if the weed has been killed by chemicals, it could return to grow again.
It is also important to remember that Japanese knotweed is classed as a controlled waste under the Environmental Protection Act 1990, which means it cannot be added to your home compost bin or council-run garden waste bins. It is only allowed to be disposed of at authorised landfill sites.
For this reason, it is best to contact a PCA-accredited Japanese knotweed treatment specialist, who can remove the weed using an approved method of eradication and dispose of it at a licensed site.
The key to successful Japanese Knotweed Removal is a sustained effort over many years. This will be more effective than simply using one eradication technique and will allow you to get your land back in a better condition. It is also worth noting that if you are planning to sell your property, mortgage lenders may require you to declare the presence of Japanese knotweed and provide a management plan for its eradication.