IN THE UK homeowners must remove Japanese knotweed if it is causing nuisance to neighbours and there are many other rules relating to the plant, considered to be one of the most invasive. Are there similar rules here? It is encroaching on our holiday home’s garden from a vacant neighbouring one and damaging the surface of the lane. The owners believe it to be bamboo and think it is not a problem. D.R.
There is only one invasive plant with laws relating to it, water primrose (la jussie), though mainly concerning a ban on sale. Japanese knotweed is called la renouée du Japon, and while its stems resemble bamboo, it is not related. A technician from the parks department of Morbihan council, which is warning against the plant, said mairies were increasingly aware of problems caused by knotweed and courses were available for staff on dealing with such species. Many local councils have called for laws to be introduced relating to it, she said.
Your mairie should be able to advise and may ask your neighbour to remove the plant especially if, as is possible, there are local planning bylaws relating to invasive plants. Its staff may also be able to intervene, especially if the plant is invading public space such as the lane.
There may not, however, be specific legal recourse concerning the plant invading your garden, because encroachment laws relate to trees.
You could seek further advice from the experts at the Conservatoire Botanique de Brest (www.cbnbrest.fr – scroll down for the Union Flag).
Should you wish to tackle the knotweed yourself, the technician said it is best to dig it up in early October. However, do not leave any of it behind as it will regrow; bearing in mind roots can be a metre deep.