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Giant Knotweed

Giant Knotweed

What is Giant Knotweed?

Giant knotweed (Fallopia Sachalinensis) is a striking and very large plant, forming stands of largely un-branched stems and bearing leaves up to 3 times larger than those of Japanese Knotweed. These are reminiscent of the foliage of the broad-leaved dock, Rumex Obtusifolius. The flowering of both male and female plants starts later than Japanese knotweed, and flowering is less prolific.

This plant is native to the island of Sakhalin to the north of Japan and the remote island of Ullung-do between Japan and Korea.

Why is Giant Knotweed a problem in the UK and Ireland?

Giant knotweed spreads by the extension of the rhizome system and is mainly dispersed by the transport of portions of rhizome to fresh sites, however it has not shown the destructive competitiveness of Japanese Knotweed.

The role of true Giant knotweed seedlings in the spread of the plants in the UK has received little discussion, though it is likely to be insignificant. Substantial genetic diversity in the plants has been noted, though this is likely to have arisen through multiple introductions of the species from various parts of the native range, rather than through home-produced seedlings.

Giant knotweed’s true significance is as the main pollen parent of the hybrid, Fallopia X Bohemica, whose hybrid vigour may render it the greatest threat, so far, of all.


Think you could have Giant Knotweed on your land? Click here to identify Giant Knotweed.


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Japanese knotweed growing in front of houses in London


Do you have Japanese Knotweed? Has your buyer’s mortgage been refused? TCM supply eradication solutions for homeowners.

Japanese knotweed rhizome


TCM provide science based solutions to a wide range of industries including construction, rail, road and the London Overground.

Howard Downer, MD of TCM Ltd


Howard Downer, AKA Dr. Knotweed, has over 20 years of experience as an Environmental Consultant and is regarded by his peers as one of the most knowledgeable people in the Japanese knotweed industry.

Follow Dr. Knotweed to hear of about the latest developments regarding Japanese knotweed and the implications of infestation.

Latest Residential Case Studies

  • Japanese knotweed growing in front garden of a London home

    Japanese knotweed – London

    Japanese knotweed was growing in the front garden of a North London property. The homeowner wanted to sell in 2017…

  • Image of a Japanese knotweed survey being undertaken

    Homeowner Wishing To Sell

    Has your mortgage been refused? TCM helped a homeowner who was wishing to sell his property but had Japanese knotweed…

Latest Commercial Case Studies

  • Japanese knotweed Soil Screening Project in Dorset

    Soil Screening Project, Dorset

    TCM soil screening project – eradicating Japanese knotweed at the site of commercial home building project Devon, UK.

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    Brownfield Site, Glasgow

    Commercial soil screening project. TCM were commissioned by a Commercial company wishing to develop a brownfield site in Glasgow, Scotland.…

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