Skip to main content

Japanese knotweed rears its ugly head

By 5th June 2023No Comments

Environet, a company specialising in treating Japanese knotweed and other invasive species, has devised a UK heat map where you can see Japanese knotweed invasion in your area. You can also notify them if you have a suspected occurance or sighting. To see the map, click here:

Japanese Knotweed UK Heat Map | Environet (

Knotweed is a highly invasive species which can have serious implications for our own flora and fauna, outcompeting them for water and nutrients and cutting off access to sunlight. Its extensive root system can also penetrate concrete and building foundations, damaging infrastructure and leading to expensive repairs. Furthermore, it can have negative effect on house prices with some lenders refusing to provide mortgages on properties with significant Japanese knotweed infestations. Factors such as climate change, urban development, and transportation of contaminated soil or plant material contribute to its spread and establishment in new areas.

Japanese knotweed grows at an alarming rate: up to 10 cm IN A DAY during the peak growing season in late spring and early summer. It continues to grow all the way through until late summer.

Getting rid of knotweed is difficult and its disposal requires proper handling to prevent further spread. Its extensive underground rhizome system allows it to regenerate from small fragments, making traditional removal methods ineffective. Effective management often requires long-term and specialised treatment approaches, which can be time-consuming and costly.

Treatment methods include herbicide application and excavation and removal but usually require a professional to administer.

At PSP, we have a specialist Stem Injector Kit that can be used to deliver herbicides into the hollow stem of the Japanese knotweed. Surface-level treatments are shown to be ineffective and also cause a threat to healthy surrounding (and desireable) plants and vegetation. By injecting herbicide into the stem, it is delivered directly to the roots and rhizomes of the Japanese knotweed where the plant’s growth and reproductive processes occur. This targeted application increases the effectiveness of the herbicide treatment. With the use of the Dosimeter valve, a very precise dose can be delivered every time which means there is no wastage of the herbicide product.

The kit, which includes a 7.6L compression sprayer, the Dosimeter and the Stem Injector Needle, is easy to use and assemble.

Find out more about the Stem Injector Kit for tackling Japanese knotweed here.