Himalayan balsam is the tallest growing annual plant in the United Kingdom and is highly invasive due to its unique seed distribution method and its ability to grow 3 meters in height in a 3 month period.
It is commonly found adjacent to watercourses, in damp ground and increasingly on roadside verges. The plant has an explosive mechanism by which ripe seeds are hurled from the plant, to enlarge the colony or be carried away by water to fresh ground.
In the case of Himalayan Balsam, seeds may be thrown 2 metres. As it is an annual, it has no other reproductive method other than seed, and thus prevention of seeding is the key to control.