West Wales News Review — analysis with a sustainability slant

Japanese knotweed invasion defeats council finances

See also the Carmarthenshire Herald, July 29th, p.2

If you see menacing Japanese knotweed on private land near your property, don’t think about asking the council to issue a Community Protection Notice. Carmarthenshire’s Executive Board agreed this week (July 26) not to get involved in problems of Japanese knotweed, and other invasive non-native plants, like Himalayan balsam, on land it does not own. The council will continue to remove Japanese knotweed from its own properties.

Japanese knotweed can grow a metre a month, a new plant can appear from a single centimetre of chopped stem, and in 2015 the UK government estimated that national eradication would cost around £1.5 billion. The cost and work involved in removing the weed can stop property sales and blight whole areas. The plants can crack concrete and other construction materials, and crowd out other species, diminishing biodiversity.


Japanese knotweed can grow as fast as one metre a month 

Carmarthenshire’s problem is lack of money to tackle both Japanese knotweed and Himalayan balsam, which have been spreading over the county, especially along the banks of rivers and streams. The Executive Board is asking the Welsh Local Government Association to urge the Welsh Government to find more cash for the control of invasive plants, which the Home Office now regards as an anti-social behaviour problem.

The Home Office does not go so far as to blame the plants, but places responsibility on owners of land which the weeds have invaded. The Anti-social Behaviour, Crime and Policing Act 2014 gives local councils and the police power to order landowners to control invasive species, by issuing a Community Protection Notice which, if ignored, could trigger a fine – as high as £20,000 for companies.

But the county council is very wary of using Community Protection Notices for weed control. Legal advice to the Executive Board pointed out that there are “few means available to landowners to physically tackle Japanese knotweed, and these are of limited effect”. It is quite possible, the Executive Board heard, that the requirements specified in a notice might not work. The available methods are also expensive, which would provide recipients of a notice with a valid ground of appeal.

Council experts concluded that investigation and enforcement to remediate invasive species would be very time consuming and “therefore very resource intensive on the officers of the section”.

Individuals and groups do have the possibility of pulling a ‘community trigger’ to require a local authority and the police to undertake a case review and consider what can be done to resolve the problem, so Carmarthenshire might yet be drawn into this knotty issue.

That is, if the insect attack fails. Plant lice called Aphalara itadori have been imported from Japan to feed on knotweed infestations. The idea is for the lice to weaken the plants so that their growth is stunted, the BBC reported last week.

This is a foray into the unknown, because no one knows exactly how the lice will react with plant and animal life in their surroundings, but other methods have failed to stop the inexorable spread of the weed pest.



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2 thoughts on “Japanese knotweed invasion defeats council finances

  1. Apologies for the delay, fascinating comment. I had read that frequent cutting makes it much less vigorous — but that generally means voluntary cutters because councils don’t have the money to fund eradication. Some new research programmes on usage would seem a great idea, given the escalating extent of the plant. Maybe Swansea University — apparently the Upper Swansea Valley is notorious for knotweed infestation.

  2. Sian Caiach on said:

    This certainly is a big problem but looking at the legal situation for Knotweed it specifies that it is unlawful to encourage it in the “wild” or spread it by removing its roots which are rhizomes, a tiny portion of which can grow back an entire plant. I’m not sure that allowing to grow into next door’s garden is encouraging it in the wild and CCC has certainly not been helpful where Knotweed has spread from its own land into neighbouring private properties, simply treating the source not the spread.

    It was originally imported as an asparagus substitute and produces similar spears before the huge bush emerges. It is not poisonous. I have tried the spears well boiled and its similar to asparagus but not by my personal taste, as nice.

    It is fantastically rampant here and maybe we could innovate to take advantage of the bounty?. As collecting the green part of the plant without roots or intention of releasing to the wild is perfectly legal, isn’t it time we started using it for animal fodder or a dried form for Holland and Barrett? The spears look quite phallic and certainly appear to put on a few centimeters quite rapidly, with no effort.

    CCC only deals with it using toxic weedkiller, usually, but it can be dealt with by cutting down to the ground several times a year which probably does the job of weakening just as well as natural invertebrate hosts, and has the advantage of being more focused. When found on verges it never seems to spread into fields with livestock,either they eat it or trample it or both. My own pet goats are partial to it but it does have a laxative effect if they eat a lot of it. Another research opportunity for Holland and Barrett?

    Cutting it carefully by hand and disposing responsibly should at least be considered and landowners encouraged to do so without danger to their pets, livestock or watercourses. One local here in Pwll eradicated it by stamping on all the spears when they emerged spreading from adjacent land. After a few years it gave up the invasion plan.

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