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Japanese Knotweed

Volume 522: debated on Tuesday 16 October 1990

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242 pm

What progress has been made in reducing the spread of Japanese knotweed.

The Parliamentary Under-Secretary of State, Department of the Environment
(Baroness Blatch)

My Lords, Japanese knotweed is a troublesome pest which grows in much of Wales and parts of England Control by a combination of rigorous cutting and grazing has met with some success. More significantly, however, chemical control appears to offer the most likely chance of success.

My Lords, I thank my noble friend for that comparatively satisfactory reply. Is she aware that a lot of research is being conducted by the Welsh Development Agency in association with the National Rivers Authority? Can the Minister say whether there is any co-operation with the French in the matter as they are experiencing a similar problem?

My Lords, I am aware of the considerable amount of work taking place to find a biological solution rather than a chemical one. I am not able specifically to answer about the European damage. I shall write to my noble friend.

My Lords, is the Minister aware that I have seen quantities of Japanese knotweed marching up the embankment of the Piccadilly Line towards central London? Is she also aware that I observed considerable quantities in central France near Dijon? Could it possibly be a secret agricultural weapon?

My Lords, the mind boggles at the thought of Japanese knotweed marching anywhere. The serious point is that anybody who suffers from having this weed in their garden has a nasty beast to contend with. It grows to about nine feet tall and its roots go down many feet There may be those who do not like chemical solutions to these problems, but I have to say that a chemical called glyphosate has been used on Japanese knotweed with some success at Ruislip and at another site in Cheshire. Reasonable success has been achieved there; and at a place called Bay Pond total success has been achieved. I suspect that the degree of the establishment of the knotweed has a lot to do with the level of success of the chemical.

My Lords, cannot the weed be eliminated just as competently without using any chemicals by cutting it two or three times every year for two or three years?

My Lords, the noble Lord is referring to control of the weed. Cutting annually and grazing will only control the weed All the evidence shows that cutting, grazing and even cutting annually will not eliminate it.

My Lords, can the noble Baroness tell the House what Japanese knotweed looks like? We want to search our gardens to discover if it is there.

My Lords, my limited information tells me that it has a stalk rather like rhubarb; that it is pale in colour and hollow in the centre. It grows tall with clusters of leaves, and at certain times in the year it produces a white flower. That makes the weed sound attractive, but I assure your Lordships that if it is in your gardens you would not find it attractive.

My Lords, is my noble friend aware that one of the problems with knotweed is that it can force its way through tarmacadam?

My Lords, my noble friend is right That is of concern because knotweed is found on much of the derelict land in this country which is being developed. Therefore, finding a solution for its elimination rather than its control is important.