Japanese Knotweed Treatment, showing buds of early growth in Spring

Japanese knotweed treatment

Japanese knotweed treatment

Japanese knotweed is a plant that did not originate in the UK. Which makes it a non-native species. A topic of regular conversation within the land based sector, it is important that you know how to identify the plant and your legal responsibilities.

Originating in Taiwan, Northern China, and Japan (funnily enough) it was introduced into Europe in the 1800s, where a plant was sent to the Royal Botanical Gardens in Kew (1850). From there, records show that it arrived in Royal Botanical Gardens Edinburgh and was being sold from a nursery in Kingston (1854). The irony is it is now quite rare in Japan and you certainly can’t sell the plants anymore!

Again as with other non-native species such as Giant Hogweed it is an architectural plant and the appeal for not only its attractiveness but its ability to stabilise areas such as bankings and sand dunes when first introduced was of great appeal. 

Fallopia japonica its scientific name belongs to the Polygonaceae family. It is often mistaken for Fallopia baldschuanica (Russian vine).

Interestingly, the genus Polygonum’s name may possibly refer to the swollen nodes on the stems. The Greek poly means ‘many’ and gony means ‘knee’ or ‘joint’

The Polygonaceae family contains some of the most prolific species and come with their own set of problems, despite the wonderful appearance of many. 

The issue with Japanese knotweed

As a non-native species that has been thriving, and almost running rampant for nearly 200 years in the UK, it is extremely difficult and at times very expensive to control. 

In Japan, its home, or native habitat has at least 30 species of insect and 6 fungus species that feed on it and keep it under check. 

However, outside its native habitat, it has no natural predators and has happily naturalised into the wild. 

Japanese knotweed plants in the UK are all female, there are no recorded males plants in the UK. So any seed produced is not viable (thankfully!)

Identification of Japanese knotweed:

Japanese knotweed as mentioned can be confused with other plant species such as Russian vine, Himalayan honeysuckle to name a few. There are also other cultivars of Japanese knotweed, Fallopia japonica var. compact which is less of a nuisance, but still requires some level of control. 

  • Leaves:
    • shield-shaped 
    • flat base
    • zig zag leaf stems
    • 10-15 cm
    • quite a small leaf 
    • lush green in colour 
  • Stems:
    • purple speckled stems
    • hollow stems
    • regular nodes (like bamboo)
    • can reach heights of 3 – 4 metres
  • Flowers:
    • small
    • cream or white
    • erect racemes
    • 6-15 cm
    • late summer, early autumn flowering
  • Seeds:
    • it does not produce seeds in the UK
    • it is spread solely by vegetative means, usually by people

A fantastic identification sheet for Japanese knotweed is available through the GB Non-Native Species Secretariat website, we highly recommend printing off and having a copy to hand.

Choices of treatment

When it comes to Japanese knotweed treatment is it extremely important that you appreciate its listing under the Wildlife and Countryside Act 1981, Schedule 9. In England, Wales and Scotland.

Furthermore, as such, it is an offence to plant or otherwise cause this plant to grow in the wild. You could be issued with an Anti Social Behavioural Order (ASBO) if you don’t keep plants on your land under control!

Finally, it is also under the Environmental Protection Act 1990. Resulting in it also having classification as controlled waste. 

All these points mean you have to consider treatment methods very carefully and your responsibilities within the law. 

Traditionally, commercial and larger scale control has been through spraying the plants:

However, it takes a few years to achieve some level of successful treatment. Control on non-native species should be completed in a timely manner in order to keep everyone safe. The RHS can some guidelines on smaller-scale traditional clearance and control. 

As a result, more and more people are choosing to use stem injection, as the preferred method of Japanese knotweed treatment. 

Our PA6inj course is an exciting new way to complete the safe use of stem injection equipment course for Japanese knotweed treatment. 

Session one is online blended learning via our candidate portal covering the theory and practical application, through fabulous videos and a detailed workbook:

  • stem injection equipment
  • needle choice 
  • calibration 
  • protection of water bodies
  • importance of using pesticides with aquatic approval
  • completing application records
  • and so much more

Session two is where you attend a face to face practical assessment.

The courses run every month, so you can work the training in and around your work calendar. The prerequisite to this stem injection course is the PA1 Safe Handling and Application of Pesticides

If you haven’t already got your PA1 we would recommend doing both together. 

Remember biosecurity when it comes to working with Japanese knotweed:

  • leave sites clean, wash footwear and vehicle tyres before leaving the site
  • clean any tools and equipment on site
  • know how to identify the plant in all seasons
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