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At Soilutions we offer a range of treatment options for invasive species including Japanese Knotweed and Giant Hogweed.  The correct treatment for your invasive species problem will depend on the nature of your problem and the circumstances specific to your site.  

What are invasive species?

They’re known as invasive species because they were introduced into this country from other ecosystems and due to the lack of natural predators or disease have been able to spread and out compete native plants. This has the effect of reducing biodiversity, impacting upon the environment and devaluing and damaging property in the process.

What can we do about this?

Once the extent of the problem has been established there are a range of solutions available, broadly these consist of:

On site herbicide treatment:  This is often the most cost effective solution available but it will take in the order of 5 years to completely eradicate most Japanese Knotweed infestations, including a monitoring period following treatment.  Giant Hogweed will often require less treatment but will also require a monitoring period in case of regrowth from seeds in the soil. 

Excavation and treatment on-site:  There are a range of variations available for this methodology and the best option will depend upon your site but essentially it involves carefully excavating all the plant material and surrounding soil, treating the resultant arisings and monitoring to ensure that there is no regrowth.  Burial at depth and containing the excavated soils within plant resistant membranes are also options. 

Off-site disposal:  This is a quick and relatively simple solution involving the careful excavation of the plant material and contaminated soil and subsequent removal to a suitably licensed landfill facility.  Due to the increasing cost of disposal of contaminated soils this is often financially unviable.  A process of screening and onsite treatment can be utilised to reduce the volumes of soil thereby reducing the disposal costs.  With Giant Hogweed mechanical removal of the plants themselves is also an option but this must be done by suitably protected persons at the correct point in the growing season to be effective.

Why are plants like Japanese Knotweed and Hogweed a problem?

They are a problem because Japanese Knotweed and Giant Hogweed are difficult to kill, can spread rapidly and if excavated and removed from site, soils containing viable plant material must be treated as controlled waste.  Japanese Knotweed spreads vegetatively (by growth or movement of live plant material by human action or natural causes such as being washed along water courses) and can regenerate a new plant from fingernail sized fragments of rhizome (root).  Crowns (the lumpy bit at the base of the stalks) and green stalk material can also re-grow to form new plants.  The plant grows very quickly (up to 40mm a day!) and can damage physical structures such as buildings and pavements, it laughs at tarmac and grows through and widens cracks and weaknesses in concrete.  It also outcompetes and damages existing natural ecosystems and when the stalks die back in autumn the resultant build up of dead and plant material can contribute to flooding problems and offers a habitat for vermin. 

Giant Hogweed presents a risk to human health with sap that on contact makes skin photoreactive leading to painful blistering and severe skin irritation resulting in purple black scars.  Symptoms of this can persist for years after exposure.  Giant Hogweed spreads from seeds, and a single mature plant can produce up to 50,000 of them which will commonly remain viable in the soil for 7 years but have been found to be viable after 15 years. 

Why do I have to do something about it?

Under the section 14(2) of the Wildlife and Countryside Act 1981, it is an offence to ‘plant or otherwise cause to grow in the wild’ any plant listed in Schedule 9, Part II. This includes Giant Hogweed and Japanese Knotweed.  This means that although it’s not illegal to have these species on your land you are responsible for preventing their spread from your land.  Given the spectacular abilities of these plants to spread, particularly if they are disturbed during site development works it is a really good idea to seek professional advice rather than risk prosecution and a sizeable fine by inadvertently spreading the problem both on and off your site.  It’s also worth bearing in mind that invasive plant species on your site is a problem that will only get worse with time, without human intervention it is extremely likely that these plants will simply continue to spread.

At your request we will provide a detailed options appraisal tailored to your site to allow you to choose the remediation option which best suits you.

Please email us at info@soilutions.co.uk, and/or feel free to give us a call (0131 538 8456), we’re more than happy to discuss your problem and help identify the best solution for your site.

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