St. Andrew's Douzaine, Guernsey

Noxious Weeds and Japanese Knotweed

Noxious Weeds


Noxious weeds can be either poisonous to humans or livestock (e.g. ragwort) or able to reproduce very rapidly to the detriment of other species (e.g. Spear Thistle).

The Noxious Weeds (Guernsey) Law, 1952 states that an occupier of land must not allow noxious weeds that are in flower or seed to grow on that land.

The noxious weeds specified in the law are Common Ragwort, Hemlock Water Dropwort, Spear Thistle, and Creeping Thistle.

A leaflet on noxious weeds is available from Agriculture, Countryside and Land Management Services. It contains information on the control of these plants.  The department may issue a notice requiring noxious weeds to be cleared.

Please contact the above department if you require further information on the identification and control of noxious weeds.




Japanese Knotweed


Although, at the time of writing, Japanese Knotweed is not listed as a noxious weed under the Law, the Douzaine is most concerned that this extremely invasive and destructive weed should not infest the Parish or indeed, the Island in general.

Japanese Knotweed or Asian Knotweed (Fallopia japonica, synonym Reynoutria japonica),  is a large, herbaceous perennial plant of the knotweed and buckwheat family Polygonaceae. It is native to East Asia in Japan, China and Korea.

Travellers to the Continent and the UK will have seen large tracts of this weed alongside roads and hedges and on waste land. It has a really wide-ranging and very deep root system, which can extend up to 7-8 metres.  The two photos below were taken in Guernsey, so we can’t afford to be complacent.

The roots can pose a very serious threat to construction works and also have devastating consequences to building foundations and drains.  The DEFRA has estimated that any attempt to eradicate this weed could cost the UK Government around £1.5 billion, and that’s without any guarantee of success.  The annual cost to the UK economy from Japanese Knotweed is thought to be approaching £200 million.  Parishioners are therefore, urged to deal with any incidents of this plant with the utmost urgency; eradication of this plant, although not impossible, is extremely difficult.  Please refer to the Agriculture, Countryside and Land Management Services at Burnt lane, St Martin, should you require further advice. Tel. 01481 235741