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What Does Japanese Knotweed Do To Humans

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  • 20-07-2022
What Does Japanese Knotweed Do To Humans

What does Japanese Knotweed do to humans? Find out if Japanese Knotweed is poisonous or dangerous. Find out if Japanese Knotweed is harmful to humans.

With a property affected by invasive plant species, you have precious time to rectify the issue. This plant can cause significant damage to your property, but is it harmful to humans?

Keep reading this article if you find yourself battling against Japanese Knotweed. 

Is Japanese Knotweed poisonous?

Many homeowners worry about Japanese Knotweed damage in their garden and outdoor spaces. As more people deal with Japanese Knotweed invasions, we are led to ask, 'is Japanese Knotweed poisonous?'. 

If we are handling and touching this invasive plant, how many precautions do we have to take to avoid family harm and illness?

Thankfully, Japanese Knotweed is not poisonous, meaning removing this nuisance plant after a knotweed infestation is not dangerous to touch or pick. 

Unlike other plants, such as the non-native Giant Hogweed, which does present a risk to property owners and contains poisonous elements, removing Japanese Knotweed is not a problem in the UK. 

However, there are still risks inherent with consuming it, especially when not prepared correctly. The real threat comes from the things this plant can do to your home.

Why Is Japanese Knotweed A Problem?

Is Japanese Knotweed dangerous?

While Japanese Knotweed specialists declare this plant not dangerous to humans and animals, some people have stated experiencing mild skin irritation after interacting with it. Still, it's worth noting there are no health risks associated with Knotweed material.

In fact, many people eat Japanese Knotweed, and this plant is used in recipes like Knotweed crumble and Japanese Knotweed beer, both incredibly popular in Asian countries.

There have been few specific health benefits associated with eating the plant, from herbal treatment for Lyme disease and lowering cholesterol in humans. Many recipes online outline how to prepare and use Knotweed in your home cooking safely. 

If you do decide to harvest Knotweed, you should remain careful. Being found foraging Japanese Knotweed (or at least aiding its spread) is a criminal offence and can result in a fine or prison sentence.

Following the foraging laws will ensure you remain on the right side of the law. You should attempt to harvest Knotweed that has been chemically treated, also. 

Confirm you understand all the legal implications and safety precautions of handling Japanese Knotweed.

However, all of that is not to say that Japanese Knotweed is without danger and risk, as it poses many threats to your building and surrounding areas. Japanese Knotweed growing rates are incredibly fast, spreading 10cm a day.

This means it can be hard to control Japanese Knotweed and, when left untreated, can spread across your home and cause severe financial and structural damage. Knotweed has been known to attack weak points in flood defences and residential property foundations. 

With an underground root system that is complicated to terminate, you can find yourself spending thousands on removing Japanese Knotweed as this plant matures. Removing this yourself is not the most effective method, and you could cause further spread of the plant. 

Is Japanese Knotweed harmful to humans?

If you have a Japanese Knotweed problem, you will be happy to know it's not harmful to humans.

However, this unique invasive plant will damage your property if you do not take care to remove it. While some people can experience skin irritation after touching it, most will not have any symptoms. Giant Hogweed is similar to Japanese Knotweed but is much more dangerous.

Giant Hogweed's sap is known for causing blisters, rashes and even blindness in some people in extreme cases. For that reason, you should identify the foreign invader in your garden before attempting Knotweed removal, as there are some foreign and native plants you can be harmed by. 

Is Japanese Knotweed Harmful To Humans?
Is Japanese Knotweed Poisonous To Pets?

Is Japanese Knotweed poisonous to pets?

If the plant is no threat to our homes or ourselves, how about common house pets? As animals eat Japanese Knotweed while on their garden explorations, how will it affect their health?

Thankfully, after animal consumption, many dogs and cats will not be harmed or experience any adverse side effects.

When consumed by grazing animals and humans alike, the knotweed taste has been compared to rhubarb or a similar lemony flavour, with the plant's seeds being used throughout many recipes.

Many plants in and around your garden create a risk to your pets, but this invasive species is not one.

However, your pets can lead to undue dispersal of the seeds and species, meaning your dog can spread it throughout your garden or even around the neighbouring parks and woodland walks. This is why you should take with your pets in the garden if you have a history of Japanese Knotweed. 

Is Japanese Knotweed poisonous to livestock?

There are many reports of livestock eating Knotweed. You will be grateful to know that livestock and grazing animals like cows and goats are at no risk from eating Knotweed, but they should do so with caution.

The plant's seeds cannot properly germinate across England, so the plant multiplies through its rhizome system, meaning plant foragers can actually cause it to spread further.

The rhizomes (plant stems) spread through the underground roots being disturbed by animals like livestock.

The plant is typically more edible as a young tender stem throughout the earlier months of the year. As the plant matures and the stem toughens while the weather becomes warmer, the stem hardens and can cause abrasions in the mouth.

If you are concerned for your livestock, ensure you are removing the plant within the law pertaining to the removal of non-native species. Allowing animals to eat it can make your infestation much worse.

Is Japanese Knotweed Poisonous To Livestock?

Why is Japanese Knotweed so dangerous?

The Wildlife and Countryside Act 1981 outlines that non-native plants (such as Japanese Knotweed) are an offensive to plant or be caused to grow due to their invasive and dangerous nature. As addressed above, Japanese Knotweed is not poisonous or toxic to humans after consumption, but it causes significant risk to neighbouring plants and outside gardens.

This plant causes issues along riverbanks and during flooding, too. As the stems die, it can exacerbate flooding when large bank areas are exposed to the surface and elements. Japanese Knotweed has the incredible yet irritating ability to spread and create vast monocultures. 

This plant's ability to disperse is impressive because the female plant is the only type introduced to the UK, meaning it only spreads from cuttings. 

This means human interference is the main contributing factor to the spread of this invasive species, with fly-tipping being another contributor to how it spreads. The plant can spread incredibly fast, sometimes after contact.

You should ensure you don't transport any seeds off the property, as doing so can go against the Environmental Protection Act and the Environmental Protection (Duty of Care) Regulations. Japanese Knotweed Removal costs can vary depending on the affected area's size, but this can cost homeowners thousands such a service. 

How To Remove Japanese Knotweed

You cannot simply place Knotweed in the regular rubbish bins you use at home, as this is illegal. Knotweed is considered controlled waste and must be disposed of correctly, ensuring no further spread is allowed. 

To remove completely, Knotweed needs to be burnt on-site or cut down by a professional, being taken to an incineration facility. When being burnt, ensure the plant has no contact with the soil.

If you are suffering or there is an infestation in your neighbour's garden, it is time to contact professional help, as they will make getting rid of it much more straightforward. Settling legal matters on whose responsibility it is to remove the species can waste enough time that t spreads further regardless, so acting efficiently is vital.

The presence of this plant can push back house sales and make moving out much more challenging for you.While eating it may not be poisonous, and leaving your livestock to handle may seem cheaper, there is still a risk of spreading it and causing illness whilst eating.

Please get in contact with our team if you require professional assistance in removing Japanese Knotweed. We are an experienced firm and can provide efficient and safe knotweed removal with an insurance-backed guarantee. 


Do you have a Japanese Knotweed problem? If you require Japanese Knotweed Removal in Essex or throughout the UK, contact our expert today.