Himalayan balsam

Beautiful but not welcome

The example above was found beside the river Derwent in Forge Valley, North Yorkshire.

Introduced to the UK in 1839, Himalayan balsam is now a naturalised plant, found especially on riverbanks (in this case the River Derwent, North Yorkshire) and in waste areas where it has become a problem weed.

Himalayan balsam tolerates low light levels and also shades out other vegetation, so gradually impoverishing habitats by killing off other plants.Himalayan balsam is considered an invasive non-native plant and is listed on Schedule 9. Under the provisions made within Schedule 9 of the Wildlife and Countryside Act 1981.

The flowers of Himalayan balsam produce large amounts of nectar and are therefore very attractive to numerous bee species.

Himalayan balsam is a tall growing annual, 2-3m (6-10ft) in height. Between June and October it produces clusters of purplish pink (or rarely white) helmet-shaped flowers.

The flowers are followed by seed pods that open explosively when ripe. Each plant can produce up to 800 seeds. These are dispersed widely as the ripe seedpods shoot their seeds up to 7m (22ft) away. Once established in the catchment of a river the seeds, which can remain viable for two years, are transported further afield by water.