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Japanese Knotweed

Knotweed in Devon

Originally native to the countries of Japan, North China, Korea and Taiwan, Japanese Knotweed is now widespread across Europe from southern France and Northern Italy to Norway, in many states in the USA from California to Washington, throughout Canada and now New Zealand where it is spreading rapidly and causing enormous problems. In its non-native situation it has no natural diseases or grazers and it flourishes.

In Britain it has now been recorded in over 50% of the 10 km squares used to map plant distribution. The only place it is not found is the Orkney Islands.

Devon is experiencing its own problems with the plant and it now occurs in most parts of the county. It is mainly found in gardens, on road verges, river banks, railway embankments and waste ground. Japanese Knotweed on the River Exe

Distribution map

This first map shows the known distribution of Japanese Knotweed in Devon in 2011. It occurs in gardens, on road verges, railway embankments, riverbanks and waste ground.

This second map shows the currently known distribution of other invasive knotweeds in Devon. However, this is likely to significantly under-estimate the extent of some of these lesser known knotweeds, so this map will change as our knowledge improves.

Recording

Without surveying and recording the distribution of Japanese Knotweed there is no way of knowing where it occurs, whether it is increasing and the typical habitats it colonises. Knowing the full extent of the problem of Japanese Knotweed colonisation in the county will help the Devon Knotweed Forum identify priorities for control and management. It is therefore important to report any sightings of the plant in the county to the Devon Biodiversity Records Centre.

If you know of a colony of Japanese Knotweed (or one of its relatives) in Devon please record its location and associated details using our recording form - click on the 'Recording Knotweed in Devon' link below.

Gallery

Welcome to the ‘Rogues Gallery’ which contains pictures of Japanese Knotweed around Devon. This is intended to give you a flavour of the types of places it is found in the county, it is by no means a comprehensive collection of pictures.

Japanese Knotweed in PlymouthJapanese Knotweed in ExeterJapanese Knotweed on the banks of the River Exe in ExeterJapanese Knotweed on a riverbank on DartmoorJapanese Knotweed on a road verge
Japanese Knotweed in a garden on DartmoorJapanese Knotweed in a woodland on DartmoorJapanese Knotweed on a road vergeJapanese Knotweed in a car park on DartmoorJapanese Knotweed at a pub in Exeter
Japanese Knotweed in a garden at Newton AbbotJapanese Knotweed in Newton AbbotJapanese Knotweed next to a cycle path near Newton AbbotJapanese KnotweedJapanese Knotweed on a road verge

Japanese Knotweed Homepage