Himalayan balsam

Himalayan balsam (Impatiens glandulifera) is one of the worst invasive plant species in the UK. It can grow from a seed to full height in one growing season and has projectile seeds that can be released up to 4m away. Its preferred habitat site is by rivers and it uses them for easy dispersal downstream to other sites. It can also grow up to 2.5m high, outcompeting other wild plants for light and dominating the area.

It also has a ten times higher rate of nectar production compared to the next best UK competitor. This may sound good - lots of food for bees! However, through this it swamps the rest of the pollen market and takes visitors away from native plants. For example a study found that some wild plants in the genus Stachys located in the same habitat as Himalayan baslam got 50% fewer visitors. Less visitors means less seed set for plants - so lower reproductive success for the natives and even higher reproductive success for the balsam. 

Due to these factors, Schedule 9 of the Wildlife and Countryside Act in England and Wales states that is is illegal to plant or facilitate the spread of this species. 

It is REALLY fun to pop the seed pods though...