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 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 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.
Japanese Knotweed growing from chipped remained
Japanese Knotweed growing from chipped remained

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 causes 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.
Japanese knotweed consumes an area and grows to over 3m in height
Japanese knotweed consumes an area and grows to over 3m in height

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 is 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 significant reduction of value to both property and land.
  3. Mortgage companies have been known to refuse lending 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 grow is eliminated over time.
  5. It is against the law to allow the spread Japanese Knotweed and you can be prosecuted if it goes on your neighbours 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 on 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 – knotweedremovaltips@gmail.com

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

Bestseller No. 1
Bayer Garden 2 x Path, Patio & Drive Weed Killer & Watering Can Set - 3 x 8g Sachets per pack treats upto 75sqm - Kills Ground Elder, Nettles, Docks, Couch Grass & Japanese Knotweed.
  • This exclusive twin pack and 9L Watering Set is everything you need for clearing weeds from paths, patios and rives including areas of tarmac, concrete and block paving.
  • Kills tough weeds and their roots including: Ground Elder, Nettles, Docks, Couch Grass, Japanese Knotweed, Brambles, Bracken & Ivy.
  • Each box contains 3 x 8g Simple ready measured soluble doses and treats up to 75sqm. Apply at any time when weeds are showing green leaf and are actively growing.
  • Sold with our durable 9L or 2 gallon capacity galvanised steel watering can with removable brass rose. Colour cannot be guaranteed. Watering can will be randomly picked and despatched.
  • Keep children and pets away from treated areas until the spray has dried.
SaleBestseller No. 2
Roundup Tree Stump Weedkiller, Super Concentrate 250 ml
  • Kills ivy japanese knotweed, saplings, brambles and nettles to the root
  • Kills up to 16 tree stumps
  • Contains a reusable pipette for specialist treatment of japanese knotweed
  • Kills the roots so weeds don't come back
  • Degraded in the soil by micro organisms
Bestseller No. 3
Scotts Miracle-Gro Roundup Tree Stump and Root Killer 250 ml Liquid Concentrate Weedkiller
  • Liquid concentrate tree stump and tough weed killer
  • Kills most garden weeds and tree stumps with a single application
  • Children and pets need not be excluded from treated areas (once dry)
  • Fully degrades in soil by microbial action
  • Leaves no harmful residues to allow replanting
Bestseller No. 4
Tree Stump Killer Root Killer Prfessional Roundup Tree Stump & Root Killer 250ml
  • Roundup Tree Stump Weed Killer 250ml Tree Stump & Root Killer Up To 16 Stumps
  • Kills stumps, trees, brambles, nettles, deep rooted and woody weeds.
  • Kills Tough Weeds to the roots.
  • Kills up to 16 Stumps
  • Roundup stump killer is a non-selective, translocated weedkiller that is absorbed by leaves and freshly cut, woody surfaces and moves throughout the entire plant, above and below the ground, to control standing coniferous and deciduous trees, newly cut tree stumps, tree saplings, brambles, bracken, Nettles, Japanese knotweed and other tough and woody weeds.
Bestseller No. 5
Bayer Garden 2 x Path, Patio & Drive Weed Killer - 3 x 8g Sachets per pack treats upto 75sqm - Kills Ground Elder, Nettles, Docks, Couch Grass & Japanese Knotweed.
  • Ideal for clearing weeds from paths, patios and rives including areas of tarmac, concrete and block paving.
  • Kills tough weeds and their roots including: Ground Elder, Nettles, Docks, Couch Grass, Japanese Knotweed, Brambles, Bracken & Ivy.
  • Each box contains 3 x 8g Simple ready measured soluble doses and treats up to 75sqm.
  • Apply at any time when weeds are showing green leaf and are actively growing.
  • Keep children and pets away from treated areas until the spray has dried.

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