Japanese Knotweed

Japanese Knotweed originates from Asia and, testament to its ability to survive in extremely harsh conditions, is the first plant to recolonise volcanic areas. It is now found in approximately 90% of the UK.

In the UK, we only have the female plant and so it relies on its root system (rhizome) to spread. This is significant because just 0.7g of rhizome material is all it takes to start a new plant and the rhizome material is viable all year round. During summer months, broken pieces of the above ground material will also cause Japanese Knotweed to spread.

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Identification

It is important to be aware that approximately 60% of Japanese Knotweed material is underground. It is easiest to identify during the growing season (April-October) because throughout the Autumn, the plant draws down reserves into the crown and roots and the visible above ground material will begin to die back. In the Winter, it is a common and costly mistake to think that the Knotweed plant is dead and no longer an issue.

Knotweed in winter
Knotweed in Summer
Knotweed in Early Spring

There are three other types of knotweed to be aware of; Giant Knotweed, Hybrid Japanese Knotweed and Himalayan Knotweed. In terms of identification, it is important to be aware that each Knotweed has a slightly different leaf size and shape when compared to Japanese Knotweed, which in ID guides is typically used for illustration. In addition to this, if a Knotweed infestation has been subject to herbicide treatment in the past, it can produce a “Bonsai” form, which will not resemble any of the classic Knotweed leaf forms.

On this basis, we strongly recommend that a professionally qualified surveyor is engaged to confirm the presence of a knotweed infestation.

 

Dealing with Japanese Knotweed

In the absence of timely identification and appropriate management programmes, a Japanese Knotweed infestation will become increasingly difficult to manage and costs will increase. Fortunately, in the hands of a qualified PCA Japanese Knotweed contractor delivering recognised best practice, the situation can be controlled at any stage of the infestation and the associated expense minimised.

Conservation Land Services Limited are here to help. Click below to start dealing with your Japanese Knotweed problem.

Commercial enquiries           Private individual enquiries

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Positive Identification

The first thing to do is to be sure it is Japanese Knotweed you’re dealing with.
As you’ll have read, recognising this plant is not always straightforward.
In our experience, the best thing to do, until it has been identified by a suitably qualified person, is to assume that it IS Japanese Knotweed and to follow the basic rules;
isolate it, don’t cut and don’t move it.

You can then email a picture to info@conservationlandservices.co.uk and we’ll very quickly be able to tell you exactly what it is and offer our thoughts over the phone.

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Early engagement:

Time is of the essence.
Wherever Knotweed is involved, any hesitancy means a bigger problem,
higher costs and more project delays.
Conservation Land Services endeavor to have a PCA certificated surveyor on site within 24 hours.

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Site mapping:

We will provide clients with a CAD generated site map, showing exactly where the Knotweed is located.
Our GPS mapping system is up to ten times more accurate than some industry equipment,
plotting site locations to within 30cm accuracy.

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Control options

The management of Japanese Knotweed focuses on dealing with the rhizome and any technique we advise has this as the key underlying principle. Conservation Land Services Limited have significant experience in all of the following techniques and, on assessment of your situation, will advise on the best method to control the infestation.

Treatment completion

“Control is only deemed complete when there have been two full growing seasons of monitoring with no evidence of Japanese Knotweed growth. At this point,  Conservation Land Services Limited will provide a certificate of completion.”