31 Interesting Japanese Knotweed Facts

As experienced providers of Japanese knotweed solutions throughout the UK, we are ideally placed to give our readers the facts about this remarkable yet horribly invasive and destructive plant.

Here are some Japanese Knotweed facts about the plant itself, its history and how it spreads.

JAPANESE KNOTWEED FACTS

1. Japanese knotweed is also known as Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a species of herbaceous perennial plant in the knotweed and buckwheat family Polygonaceae and is the most evasive weed within the UK.
2. The plant has all sorts of weird and wonderful names, including Hancock’s curse, Mexican bamboo, and the German sausage plant.
3. Japanese knotweed treatment costs the British economy millions of pounds each year to manage. And it’s estimated that the cost of controlling it could add 10 per cent-plus to a development project.
4. Japanese knotweed is a perennial plant which means it has a life span of over two years.
5. It is listed under schedule 9 of the Wildlife and Countryside Act 1981 and it is an offence to plant or cause this species to grow in the wild.

ORIGINS

1. Native to East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established itself in numerous habitats and is classified as a pest and invasive species in several countries.
2. In its native country of Japan, China and Taiwan, knotweed cause less invasive problems. This is due to it having plenty of natural predators like fungal pathogens and insects.
3. In the United Kingdom, Japanese Knotweed has no natural enemies to stop it from spreading, whilst in its native Asia, it is controlled by fungus and insects.
4. Introduced into the UK in the 1800s it has managed to spread to every corner of the UK and is considered the most evasive weed known to man.
5. London’s 2012 Olympics sites were riddled with the stuff and the developers spent four years getting it under control.
6. Survey data suggests that there’s at least one infestation for every ten square kilometres of the UK.

CHARACTERISTICS

1. During winter it sheds its leaves and its stems go brittle. Whilst it appears dead, it isn’t. Come spring it returns with a vengeance.
2. Even the smallest piece of rhizome, smaller than a fingernail can take root and regrow. Being mostly spread by people, machinery and water transporting fragments to new sites.
3. The Japanese knotweed rhizome is knotty and brown, with a surface a bit like bark which makes it difficult to spot from other roots. Inside it’s orange-brown-yellow.
4. The plant grows remarkably fast and vigorously, growing 2m-3m high each growing season, sometimes 10cm a day, with a root spread of up to 7m.
5. Japanese knotweed isn’t toxic to humans. However, due to it consuming an area comprehensively, the habitat it creates is hostile to local wildlife, birds, plants and insects. It also releases allelopathic chemicals into the soil that can stop other plants from growing.
6. Japanese knotweed can stay dormant for up to 20 years.
7. Bits of dead knotweed can take as long as three years to decompose properly.
8. The plant is so resilient it is even immune to burning and can rise from the ashes to grow once again.

USES AND BENEFITS

1. The Japanese use the plant in traditional medicine, where it’s a popular painkiller. The resulting medicine is called Itadori, which translates as ‘take away pain’.
2. It may be invasive but some use its rhubarb-like young shoots to make meals such as tarts and cakes.
3. Beekeepers in the USA use Japanese knotweed plants as a significant source of nectar for honeybees during a time of year when little else is blooming.

PROPERTIES

1. Experts estimate the loss of value to most properties are anywhere between 10% and 20% if left untreated.
2. Capable of growing through even the smallest crack or fissure, Japanese knotweed can destroy concrete, drains, and asphalt leading to a significant reduction in the value of both property and land.
3. Mortgage companies have been known to refuse to lend on properties where there’s knotweed present (thankfully this problem can be solved by undertaking a professional treatment plan with a recognised contractor).
4. To permanently remove Japanese knotweed from your property will take years not months. Requiring regular visits to ensure all growth is eliminated over time.
5. It is against the law to allow the spread of Japanese Knotweed and you can be prosecuted if it goes on your neighbour’s land.
6. Japanese Knotweed is a controlled waste that must be disposed of carefully to prevent it from spreading. It is illegal to dispose of it in an improper manner.
7. Plant material can also be transported unintentionally by machinery travelling from infested sites and is commonly spread by fly-tipping garden waste or soil that contains plant fragments.

Final Thoughts

These are just some of the main Japanese knotweed facts that show some of its main characteristics and how troublesome it can be.

If you wish to get rid of it from your property, then please do not hesitate to reach out to us or continue reading more with our comprehensive guides – The Complete Guide to Japanese Knotweed or the Step by Step Guide to Removing Japanese Knotweed Permanently.

Want to know more about Japanese knotweed?

Knotweed Removal aims to provide the most up-to-date information, help and advice for YOU to make informed decisions. If you are unsure or uncertain about how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email – hello@knotweedremoval.tips

Do not forget we have a library of blogs covering many areas relevant to Japanese Knotweed, our free downloadable How-to Guides and Product Reviews on the latest methods being employed to eradicate or remove Japanese Knotweed.

Knotweed Removal, UK

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