Tackling the alien invasion
Introduced to the UK in 1839 by Victorian gardeners who found the pink flowers attractive, Himalayan balsam has become a naturalised plant and a major weed problem, especially on riverbanks, waste land and even in gardens. It grows rapidly and spreads quickly, smothering other vegetation as it goes, impeding water flow and leaving river banks bare in winter increasing the chances of flooding.
Each plant can produce up to 800 seeds. These are dispersed widely as the ripe seedpods explode shooting them up to 7m (22ft) away. Once established in the catchment of a river the seeds, which can remain viable for two years, are transported further afield by water. Himalayan balsam has the ability to grow almost anywhere and a nationwide programme of eradication is currently being rolled-out.
In the south west there is a focus on river courses, including intensive efforts on the Camel, Tamar, Lynher and Otter. Clinton Devon Estates’ staff have been addressing the issue over many years in key conservation and forestry areas, and continue to work in partnership with other members of the community to ensure that the spread is controlled. Before tackling the main Otter River, the strategy is to drive the invasive back down the tributaries.
In early summer 2013, nearly 20 staff from the Estate offices and farms joined 40 Royal Marines from the Commando Training Centre at Lymptstone (CTCRM) and 12 volunteers from the Otter Valley Association to control the weed on some of the tributaries of the Otter River using non-chemical means, including pulling. The strategy is to slowly drive back the balsam down to the main valley area.
Clinton Devon Estates is developing an ongoing policy which outlines the environmental impact of this invasive species, its responsibilities as a landowner and how the organisation intends to deal with it in future years.
Dr Sam Bridgewater, Nature Conservation Manager for Clinton Devon Estates comments: “We don’t want to use chemical control near streams, and hand pulling is very labour intensive. Taking a partnership approach and pooling resources is the best way to tackle this problem.”