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Japanese knotweed booklet
Japanese knotweed booklet
24 Apr 2017
you can download our shiny new Japanese knotweed information booklet here :)

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Invasive Plants and Japanese Knotweed Control

Invasive plants      

Cook Group are experts at treating invasive non-native plants such as Japanese Knotweed, Himalayan Balsam and Giant Hogweed. We hold the nationally recognised CSJK qualification (Certificated Surveyors for Control & Eradication of Japanese Knotweed) within our management team, our 2 surveyors being the only such qualified persons in the Hull & East Yorkshire region. Our experienced site operatives also hold the PCA Qualified Technician qualification for Japanese Knotweed as well as PA1, PA6, PA6AW & PA6INJ credentials for the safe purchase, storage and application of commercially available herbicides.

What is an invasive non-native plant?

An invasive non native plant is one that is not native or original to the country it is growing in. Typically an invasive plant also spreads very quickly coming in time to completely dominate the area in which it has spread, all to the exclusion of other plants and thoroughly affecting the local bio-diversity. Being of an invasive (rapidly spreading) nature means it is also very difficult to eradicate or control.

Schedule 9 of The Wildlife and Countryside Act 1981 now lists over 40 invasive plants in the UK of which Japanese Knotweed is quite possibly the most serious invasive non native plant...........So now you know!

    Japanese Knotweed

What is Japanese knotweed?

Japanese Knotweed is an invasive non-native perennial plant and is dispersed widely throughout the UK. Its full Latin name is Fallopia japonica var japonica (perennial means it lives for more than 2 years)
Japanese knotweed is widely accepted as being the most invasive plant in the UK.
It was introduced into the UK in the mid nineteenth century as an ornamental garden plant from Japan (hence the use of japonica in the name). If only our Victorian gardeners had realised what they were doing when they were planting what has now become known as the most invasive 'Super Weed' in the UK!
This plant is common in Japan but does not cause anywhere near the amount of problems it does here because in its native environment it is controlled by indigenous insects, fungi and diseases.
In the UK though it is not controlled by nature and left unchecked can easily grow at up to 1 metre a month. The rhizomes (underground stems) can grow and extend to depths of 3 metres and as much as 7 metres away from the original stem location! Though in reality this can be much less.
Each stalk or cane has its own root system formed from a 'crown' which is a large surface rhizome. Combating the extensive underground system of roots and rhizomes is one of the difficulties in succesfully treating an outbreak of Japanese Knotweed.
Japanese Knotweed Growth        Japanese Knotweed Control

Where Does it Grow?

Japanese Knotweed has spread dramatically across the UK and is common in the following areas
  • Rivers, streams & watercourses (where it can contribute to flood risk)
  • Roads & Motorways
  • Wasteland
  • Brown field sites awaiting redevelopment
  • Green field sites awaiting development
  • Railway lines & embankments
  • Gardens 

Some common 'Urban Legends'....and the real truth!

During the growing season which is early spring to late October, many headlines appear in the local and national press detailing claims that Japanese Knotweed seriously damages the foundations of buildings perhaps leading to their demolition or even, spontaneous collapse!

Such dramatic headlines are simply not true. If you are researching this web page because you know or believe you may have Japanese Knotweed, or your researching a headline, then the following clear guidance will hopefully set your mind at rest:

  • Japanese Knotweed will not grow in or through an impermeable surface such as mass poured and reinforced concrete. In fact, professionals commonly use thin reinforced plastic sheeting as a root barrier to prevent Japanese Knotweed spreading from one area to another.
  • Japanese Knotweed however will certainly grow and exploit gaps or joints in any hard surface like paving stones, tarmac or old brickwork where it will grow between bricks in movement cracks. The roots and stems being vigorous in growth can then exert considerable forces over the years as they develop and exapnd within gaps, this potentially causes heaved walkways and buckled walls.
  • As a result its presence in and around properties can mean that the subject property becomes seriously devalued with some statistics for valuation noting anywhere between a 5 to 20% reduction in the overall property value. Many Mortgage Assessors place a nil value on property with Japanese Knotweed present.
  • The placement of a dedicated Japanese Knotweed Management Plan created and followed by the property owner in conjunction with a competent PCA Registered Contractor can avoid serious problems when buying or selling property.

How Do You Control It?

Cook Group control Japanese knotweed by various measures, this depends on the severity of the outbreak, where it is and environmental considerations such as nearby watercourses, trees, the local bee populations etc. We will develop a dedicated Japanese Knotweed Management Plan tailored to your needs and that of the site under your control.

The principle way we treat Japanese Knotweed is by using a programme of foliar herbicide spraying as part of a wider treatment plan, for really severe outbreaks a treatment plan can last up to 5 years and perhaps even longer. That is why we initially create a desktop action plan with our Clients so as we know what you wish to achieve for your site.
There are various other means of controlling an outbreak, crown removal, creating bunded areas, removing contaminated topsoil and laying root barrier systems.  All of these options can be combined into your bespoke Japanese Knotweed Management Plan.

Specialised Stem Injection.

One of our main forms of treatment is to actually inject a concentrated dose of herbicide directly into the cane or stem of each plant, by carrying out this treatment at the right time of year, we can gain extremely effective results and can dramatically reduce the regrowth rate. We also use this system in sensitive areas where we need to protect surrounding plants or trees from the herbicide we use. This type of treatment is known as stem injection. 

 What Are My Legal Responsibilities?

As a landowner you are not obliged by law to remove Japanese knotweed from your land. However if it is affecting a neighbouring property and is causing problems or 'nuisance' then you DO have a clear obligation to deal with it.

  • Primarily, it is an offence under Section 14(2) of the Countryside & Wildlife Act 1981 to plant, or encourage Japanese Knotweed to grow in the wild.
  • Waste plant material is classified as 'controlled waste' and should be disposed of as per the Environmental Protection Act 1990 (EPA1990), as you might expect a license is required for this and a 'duty of care' procedure is enforced.
  • The Hazardous Waste Regulations 2005 (HWR 2005). Untreated Japanese Knotweed isn't classified as hazardous waste, but when the plant has been treated with certain herbicides or the soils containing rhizomes and roots have herbicide within, then such material is classed as hazardous waste.
  • Waste Management Licensing Regulations 1994. The relevant bit of these regulations basically state that waste material is disposed of without harming the environment
  • The Anti-Social Crime and Police Bill 2014. It may be that left unchecked on your land the Local Authority or the Police Wildlife Officer of the local constabulary can make you subject to a legal action in the form of a Community Protection Notice as part of  current anti-social behaviour law so as to force you, the landowner, to resolve the Japanese Knotweed issues you are creating particularly if a sustained nuisance is being caused to your neighbours.
  • Where incalcitrant landowners allow Japanese Knotweed to have wider ecological impacts The 2015 Infrastructure Act can be used to make Special Orders to force landowners to deal with the knotweed infestation, this maybe for example where a serious infestation leads to adverse developmental costs for road and rail expansion etc.

Want more information?

If you need more information, advice or you need us to arrange a visit your property to assess the problem, then simply click on the 'Contact Cook Group' link below to where one of our Certificated Surveyors for Japanese Knotweed (CSJK) will be pleased to assist you!.

Not Sure if you have Japanese knotweed? 

Send us some pictures, try to include some close up and general photo's of the area and if it's possible for us to identify Japanese knotweed (or otherwise) then we will!

Invasive Weed Group

Cook Group are members of the Invasive Weed Group (IWCG). The Invasive Weed Control Group is a division of the Property Care Association


Image contact-cook-group.gif


Sub Categories
Sub Categories within Invasive Plants and Japanese Knotweed Control category

Identifying Japanese Knotweed
Identifying Japanese Knotweed
This section gives you information on how to identify Japanese Knotweed, including video footage
Stem Injection
Stem Injection
Stem injection is a very effective method of treating Japanese knotweed, particularly when the outbreak is surrounded by plants you want to keep
Interesting Facts About Japanese Knotweed
Interesting Facts About Japanese Knotweed
This section contains some of the more obscure information and facts about Japanese Knotweed about
Giant Hogweed
Giant Hogweed
This section tells you more about the invasive plant 'Giant Hogweed' and how we can treat it for you

Downloads within Invasive Plants and Japanese Knotweed Control category

Japanese knotweed booklet You can download our Japanese knotweed information booklet here that will give you all the information you need on this invasive plant

Todays Featured Images
Todays featured Gallery Images

Another patch of stone
Another section of chalk wall awaiting rebuilding
Another patch of stone

Fire door & dry rot
Note how the dry rot outbreak has spread through the hardwood firedoor and smokeseals
Fire door & dry rot

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