Himalayan Balsam (Impatiens glandulifera)
Native to western Himalayas, Himalayan Balsam, was introduced in the British Isles in 1839 and is now widespread throughout the country. Normally found along riverbanks but it is not restricted to such areas and prefers damp soil. It can grow up to 2-3 metres tall and is the tallest annual in the U.K, with pink / purple flowers from June to October.
Very easily spread along water courses due to its exploding seed pods. Himalayan Balsam, due to its size and density of plants growing in any given area will out compete and displace native vegetation, reducing biodiversity. Its flowers have the greatest nectar content of any plant in Europe, therefore attracting pollinators that would normally pollinate native species; again reducing species diversity. It causes erosion of river banks in winter due to lack of native vegetation and bare soil. Its exploding seed pods have a spread of up to 7 metres from the plant and are viable for 2-3 years making short term control difficult.
Due to its usual close proximity to rivers, access can sometimes be difficult. Himalayan Balsam has a shallow root system and can be hand pulled over several years to help control spread, but beware of upstream infestations which could render your efforts futile.
Herbicide application: Glyphosate .
Listed on schedule 9 of the Wildlife and Countryside Act 1981, it is an offence to deliberately cause the plant to grow in the wild.