HIMALAYAN KNOTWEED AT OTTERHEAD

Himalayan Knotweed (Polygonum polystachyum) has narrow pointed leaves, one of the easiest ways of distinguishing this invasive perennial from the more common Japanese Knotweed.

From small beginnings as photographed on 9 May 2008, the canes will reach five feet or more by the end of the growing season. It is most important not to disturb the underground roots or rhizomes as this will almost certainly lead to propagation and possibly contamination of other areas. Similarly, when the plants are growing by watercourses, bank erosion can result in root propagation; fortunately this knotweed is not close to the River Otter at Otterhead. 

Probably grown in the gardens at Otterhead as an ornamental plant for more than a century but whether the plants would be of sufficient interest to retain their place in a present-day garden, even if not invasive, is debatable. However, Otterhead has a now notorious garden plant introduced by the Victorians and deliberately planted in what was formerly a notable Victorian garden and it does at least have some heritage value, so while this stand of knotweed needs to be reduced, it and two other much smaller stands may have value as an education resource providing they are carefully monitored.

Himalayan Knotweed: emerging young canes 

Himalayan Knotweed: by the Otterhead Back Drive 23 June 2008

Coming into flower 19 August 2008 

Flowers 19 August 2008