Himalayan Balsam Impatiens glandulifera (hereafter I. glandulifera) is a non-native invasive plant first introduced to the UK in 1839. It is the largest annual plant in Britain, growing up to 2.5m high from seed in a single season. The plant has green leaves with serrated edges, large pink-purple flowers which look like policeman’s helmets and a stem which has a slight red colouration.
I. glandulifera is typically found on the banks of streams and rivers and has a highly effective seed dispersal mechanism, allowing it to project its seeds up to four metres. Ejected seeds can fall into the water before being transported downstream, allowing for colonisation there. Given the unique seed dispersal mechanism, the plant can spread quickly, often forming dense stands which can influence the native plant community. Being a shallow-rooted annual plant, it dies off during the winter months leaving exposed river banks which are susceptible to erosion during high flows. Inputs of fine sediments into rivers, due to the impacts of I. glandulifera or otherwise, can have significant detrimental impacts on a variety of aquatic life, including but not limited to invertebrates and redd-building fishes.
I. glandulifera is listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales. This means it is an offence to plant or encourage the spread of this species in the wild.
Great care is required to avoid spread when managing I. glandulifera. Mechanical (manual removal and strimming), chemical (herbicide) and biological (balsam rust) methods exist and can be used to manage I. glandulifera populations. More information on the benefits and disbenefits of each of the methods can be found using the below links.