Managing highly invasive Himalayan Balsam
H
imalayan Balsam, as the name suggests, is native to the foothills of the Himalayas and was introduced to the UK as a garden plant in the 1800s. Being highly invasive it quickly escaped and became widespread along rivers and ditches where it is a common feature during the summer months. It is listed under Schedule 9 of the Wildlife and Countryside Act 1981 which means it is an offence to plant or allow this species to grow in the wild. The plant is easily identified by its pink-purple sweet-smelling flowers, matt green leaves with finely serrated edges, and tall hollow stems. Germination occurs during early spring and the plant grows rapidly up to three metres high and flowers through the summer. From late spring/early summer seed pods form and these explode seeds over a wide distance, so managing the plant before the pods form is vital. Himalayan Balsam poses no physical risk or danger to humans or animals, but its vigorous growth outcompetes native plants for light, nutrients, space and pollinators, and when it dies back in the autumn it leaves bare banks which are susceptible to erosion leading to an increase in flood risk and a loss of habitat. In addition, the plants have very shallow root systems and can easily become washed away during flood conditions, forming blockages in the channel. Each plant forms many seed pods which each contain thousands of seeds and these can remain viable in the
18 Completely Bromsgrove
soil for up to two years, helping the plant to remain established over subsequent years. Management of Himalayan Balsam is in theory relatively easy, in that it just needs to be pulled or cut before the seed pods form, but to eradicate the plant completely from an area is difficult as it requires constant and prolonged management over the entire catchment, in areas that are often difficult to reach. The Environment Agency estimated in 2003 that it would cost £300 million to eradicate this plant from then UK entirely. In 2014 Defra approved the use of a rust fungus which impacts only Himalayan Balsam and weakens the plant during the growing season – it is hoped that over time this fungus will spread nationwide and help to provide a natural control to this invasive plant. What can you do? Next time you’re walking along a riverbank and spot this flower, if the seed pods haven’t yet formed grasp the stems low down on the plant and pull them out from the roots or snap the stem at the lowest node – the plant can then be composted or burned.
