Japanese Knotweed is a nuisance plant that can set back house sales, cost homeowners thousands in removal costs and hours of precious time in settling legal matters. Whether it is growing in your neighbour’s garden, or you’ve just bought a house with Japanese Knotweed, it’s likely that you’ll want to find out as much about this foreign invader as possible, and it’s not unreasonable to wonder whether this much-maligned plant could cause you or your family harm.

Is Japanese Knotweed poisonous?

Despite its fierce reputation, Japanese Knotweed is not poisonous. Although the plant is an incredibly quick grower and can prove to be a resilient enemy for homeowners, it does not contain any poisonous element, unlike other plants that are featured on Schedule 9 of the Wildlife and Countryside Act 1981.

Is Japanese Knotweed harmful to humans?

Japanese Knotweed is not harmful to humans, although some have reported that contact with the plant can cause some mild skin irritation. Japanese Knotweed is often confused for Giant Hogweed, which does pose a real threat to people. Giant Hogweed’s sap can irritate the skin, causing blisters, rashes and even blindness. For that reason, it’s a good idea to make sure you positively identify Japanese Knotweed before handling it in any way.

Is Japanese Knotweed poisonous to pets?

Japanese Knotweed is not poisonous to pets. There are many plants that could cause harm to your pets, but Japanese Knotweed is not one of them. Common house pets such as cats and dogs are unlikely to take a bite of the plant, but even if they do, they shouldn’t come to any harm as a result.

Can animals eat Japanese Knotweed?

Grazing animals, such as goats, can eat Japanese Knotweed however, farmers should seriously consider this option before allowing their herd to do so as animal consumption could lead to undue dispersal of the plant. Japanese Knotweed is a unique invasive plant as it is too cold for the plant’s seeds to properly germinate in the UK. The plant multiplies via its rhizome system which can reproduce from the smallest of fragments. Allowing animals to eat Japanese Knotweed could further disperse these rhizomes and exacerbate the infestation.

Can people eat Japanese Knotweed?

It is possible for people to eat Japanese Knotweed, however, there are some risks inherent in doing so. Some plant foragers have identified the best times of year to harvest the invasive plant, however, this must be done with caution. The plant is said to be edible as a young tender stem during the months of April and May. As the plant matures, the stems toughen and can cause abrasions in the mouth. Although there is a wealth of recipes online, it’s worth noting that there are few specific health benefits associated with eating it, other than as a herbal treatment for Lyme Disease and a means to lowering cholesterol.

In the event that Japanese Knotweed is harvested for consumption great care should be taken to ensure that the plant has not already been chemically treated. Those intent on foraging Japanese Knotweed should also ensure that they do so within the law pertaining to Japanese Knotweed. It is an offence to cause the spread of the plant and those who are found to do so could be fined or even imprisoned. Make sure you fully understand the legal implications of handling Japanese Knotweed before planning a foraging trip.

What does Knotweed taste like?

Botanist and columnist James Wong has reported that Japanese Knotweed has a similar ‘bright and tangy flavour’ to rhubarb and noted in his article for the Guardian that it can be served in a variety of ways including desserts, such as crumbles, or as a chutney or sauce with cheese or meat. Foragers have noted that is has a lemony flavour and can also be used in the creation of wine or beer.

Japanese Knotweed is not poisonous, but whilst eating the plant is certainly possible, it’s by no means the most effective method of removing it. Getting rid of Japanese Knotweed is best managed with the help of an experienced firm and an insurance-backed PCA-accredited treatment plan.

For more information and support contact the Japanese Knotweed Agency on freephone 03335 777 888

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Following the recent review of the EU Invasive Alien Species (IAS) Regulations, the Property Care Association (PCA) released a statement that 17 new species are being added to the list of ‘Species of Concern’ – 13 of which are plants (You can see the full list here).

This regulation contains species whose potential adverse effects across the European Union are such that concerted action across Europe is required to control them. The list is drawn up by the European Commission and managed with the Member States using risk assessments and scientific evidence. The regulation should not be confused with UK invasive alien species legislation. The GB Non-Native Species Secretariat (NNSS) has information on UK invasive alien species legislation here.

The IAS Regulation 2014 provides for three distinct types of measures to control ‘Species of concern’:

Prevention: measures aimed at preventing the introduction of IAS into the EU (e.g. restrictions on sale and supply via the horticultural trade).

Early detection and rapid eradication: Members must put in place a surveillance system designed for ‘early detection’ and take rapid eradication measures to prevent establishment.

Management: If already established, implement a management plan to prevent them spreading further and minimize the harm they cause, ecological or otherwise.

The PCA have reviewed the new plants considered “of concern” and have identified the following 3 plants, as most likely to enjoy the UK climate.

The Tree of Heaven

The Tree of Heaven (Ailanthus altissima) is already included in the PCA’s useful guide on the Practical Management of Invasive Non-Native Weeds.

Although it originates from East Asia, it arrived in the UK as a horticultural introduction in 1751. It’s prevalent in the south-east of England, especially Greater London and East Anglia. It’s mainly restricted to the urban environment where it forms thickets of inhibiting ground flora, both by shading and through the production of a toxic chemical that suppresses germination and growth of other plant species (so-called allelopathy). Roots and suckers can disrupt structures, pavements, drains and buildings, leading to it being coined “Tree of Hell”.

The Balloon Vine

The Balloon Vine (Cardiospermum grandiflorum) is a climbing shrub that is already classed as invasive in Australia, South Africa and Southern States of the USA. It was introduced around the world mainly as an ornamental plant. It escaped cultivation and became naturalised and invasive. Once established, it grows rapidly into the tops of trees, forms a thick curtain of stems, excluding light, and harbours pests and diseases. Weight contributes to canopy collapse and ecosystem destruction. C. grandiflorum is a declared noxious weed in Australia and South Africa, is reported as invasive in many other countries, and is likely to spread. This is something to look out for; there are no UK NBN records so far but one CABI record in France. It’s associated with drier climates/soils, so global warming might increase the likelihood of arrival here especially in frost-free areas.

Japanese Hop

Japanese hop (Humulus japonicus; Humulus scandens) hails from temperate-climate regions of Asia (China, Japan, Korea, Taiwan and the Russian Federation) and tropical Asia. It’s another plant already listed as invasive in North America. Like all ‘hops’ it is closely related to cannabis but unlike the common hop is absolutely no use for making beer at all (just in case you were wondering….).

Japanese hop can spread to cover large areas of open ground or low vegetation including understory shrubs and small trees. Many thousands of hop plants per acre may be produced, eventually blanketing the land and vegetation. The vines grow rapidly during the summer, climbing up and over everything in their path and can form dense mats several feet deep, blocking light to plants underneath. Hop vines also twine around shrubs and trees causing them to break or fall over. It is invasive in riparian and floodplain habitats where it displaces native vegetation prevents the emergence of new plants and kills newly planted trees installed for streamside habitat restoration. Hop can quickly cover small trees hiding them from view, preventing mowing and obstructing herbicide applications.

The government has recently confirmed that the Invasive Alien Species (Enforcement and Permitting) Order 2019 will bring EU legislation into UK law on 1 December 2019.

Lord Gardiner, the Biosecurity Minister said:

“Invasive non-native species not only challenge the survival of some of our rarest species but damage our natural ecosystems as well as costing the economy more than £1.7 billion per year.”

“The law requires management measures to be put in place and this consultation will ensure we consider the evidence on how best to manage these species of concern.”

The government say that the UK will continue to uphold international obligations and as a responsible partner nation working closely with other countries to protect our native wildlife and forestry landscapes for future generations to enjoy.

Here at Japanese Knotweed Ltd we survey, manage and control a wide range on non-native invasive species and keep track of changes to relative UK & EU law, monitoring how it may affect us and our clients.

Call us freephone 03335 777 888 or send us a message through our contact us page.

verdict of Network Rail’s appeal in the Waistell vs Network Rail case

The Japanese Knotweed encroachment case where claimants, homeowners Mr Waistell and Mr Williams, claimed against Network Rail Infrastructure Ltd in private nuisance was reinforced on 3rd July 2018, with the Court of Appeal unanimously dismissing Network Rail’s appeal.

The Court of Appeal found in favour of the two homeowners and agreed that the presence of knotweed on adjoining land constitutes an actionable nuisance if it threatens to cross the boundary, even if it hasn’t yet.

The judgment also clarified that for a nuisance claim to succeed, it was not necessary to prove physical damage to the property. The fact that Knotweed rhizomes are present on the land constitutes an interference with the amenity of the land, that is, the right to use and enjoy it .

Leading treatment firm boss said:

“Network Rail fought the original case in Cardiff County Court thinking they could win and stem the tide of claims against them. They’ve now scored two spectacular own goals and unwittingly opened the flood-gates for thousands of new claims. 

“This judgment should put all owners of land infected with knotweed on notice to take proper action to ensure their knotweed does not encroach onto or threaten other property. Those that continue to ignore the effects of their inaction and affect their neighbour’s enjoyment of their property are now fore-warned. The law is clear and substantial damages can be awarded against them.

“It is also worth pointing out that a defence in nuisance is that all reasonable measures are being taken to mitigate the nuisance. A half-hearted or cheap attempt at control is unlikely to meet the ‘reasonable measures’ test. 

“This judgment will have far-reaching implications for owners of land affected by Japanese Knotweed. It provides the legal profession with great clarity, which is likely to increase the number of merited claims and settlement of those not worth contesting. This can only be good news for those we would describe as ‘victims of encroachment’ who up to now have had to put up with bully-boy tactics, inaction and worry while their home is blighted by this invasive and damaging weed.”

Displayed from 22nd – 26th May 2018, within the Discovery Zone at the PCS’s ‘Enemy Within’ garden.

A rather beautiful plant with luscious, green heart-shaped leaves and dainty clusters of creamy-white flowers will be taking centre stage at the prestigious RHS Chelsea Flower Show this year. Among the show gardens of roses and peonies at this highlight of London’s social calendar, will be none other than Fallopia Japonica, better known as Japanese knotweed, displayed in all its summer flowering glory within the Discovery Zone at the PCA’s ‘Enemy Within’ garden.

The garden will showcase 14 invasive non-native plants which are currently thriving across the country, including buddleia, bamboo and montbretia as well as the infamous Japanese knotweed, delivering a strong message to visitors about the nature of invasive plants and the damage they can do. The exhibit will also provide insights, education and guidance about the plants, including identification, risk, pathways of spread, as well as control and preventative measures.

Profiling Japanese Knotweed and other invasive plants at such an esteemed event is a great way to raise awareness, helping people understand what to look out for and what to do if they discover Japanese Knotweed growing on or near their land. The plant grows extremely rapidly at this time of year and, depending on how much sunshine we have, it could even grow by half a metre during the show, which runs from 22nd to 26th May!

Japanese Knotweed Agency said “We are delighted to see Japanese Knotweed taking centre stage at the Chelsea Flower Show this year to help raise awareness and educate people about Knotweed. The more people are aware the more action can be taken on a country wide scale to reduce the spread and work towards total eradication of this nasty plant”.