How Norfolk Wildlife Trust volunteers are taking on the plant invaders
PUBLISHED: 10:51 09 June 2018
Since its introduction to Britain, Himalayan Balsam has spread throughout the country, says Norfolk Wildlife Trust's Reserves Manager, Steve Collin, invading wet, wild places and taking over swathes of our countryside…
The plant originated from the Himalayan mountains but, in 1839, was bought here as an exotic addition to gardens. With its tall stature and fine display of pink or purple flowers it is easy to see why this fast-growing plant was popular and widely planted.
But as the scientific name Impatiens glandulifera suggests, this is not a patient plant and it soon escaped the garden borders. Creeping along ditches and waterways, silently spreading itself.
The plant is easily recognised as it does look ‘out of place’ in our countryside. It can grow well over head height with a succulent hollow stem that is green in spring and turns red as summer progresses. The simple green leaves have saw-like serrations, tinged with red and usually grow in whorls of three. Other names for balsam include ‘gnomes hatstand’, ‘policeman’s helmet’ and ‘bobby tops’ as the purple or pink (rarely white) flowers resemble small hats.
But don’t be fooled by its pretty flowers. Balsam is aggressively competitive and very fast growing - quickly shading out native plants - resulting in the loss of biodiversity and even riverbank erosion. Colonising some of our most important sites for wildlife and suppressing rare and beautiful plants, such as marsh orchid and bog bean. It does, however, produce lots of nectar which is very attractive to pollinating insects. Bumblebees can often be seen feeding on them, with only their back end protruding from the flowers, hence another name for balsam: ‘beesbums’. But worryingly even this is thought to distract insects from visiting native wildflowers which may, in turn, go un-pollinated.
Himalayan balsam in an annual, which means it grows, flowers, and sets seed all in one season. It is not hardy and was first introduced as a greenhouse plant. The first shoots can be seen in mid-May and grow rapidly until the first frosts of autumn cause it to die back. The seed waits for winter to end and the soil to warm in spring before germinating to continue the cycle.
After the flowers are pollinated, seeds form and ripen in pods. These ripe seed pods explode when touched or are knocked by the wind, shooting seeds five metres or more, giving rise to other common names for balsam, such as ‘Jumping Jacks’ and ‘Touch-me-not’. With each plant capable of producing as many as 800 seeds that remain viable for two years, it soon invades, smothering riverbanks, marshes and other damp ground.
Himalayan balsam is so invasive that, in UK law, it is illegal to plant or encourage it to grow in the wild. And gardeners that grow the plant are encouraged to prevent it escaping their property. But being listed in the Countryside and Wildlife Act is not enough to stop the balsam advance. Every summer, teams of conservation volunteers give their time to win back our countryside.
Norfolk Conservation Corps and Norfolk Environmental Weekenders (NEWS) are two such groups that work tirelessly to rid Norfolk Wildlife Trust nature reserves and other important
sites for wildlife of the balsam menace.
Strimming, scything or pulling up by the roots effectively kill Himalayan balsam but the scale of the task and nature of the habitats, with swampy ground or steep riverbanks, make this very labour intensive work. And time spent attacking balsam is time not spent on other important wildlife conservation tasks. Volunteer groups are always after new recruits to help the fight.
Prevention is better than cure, so plants need to be cut or pulled before seed is set. Once balsam is allowed to disperse its high velocity seed, rivers and streams carry it to other sites downstream and so the cycle continues. Only cooperation between landowners and countryside managers to coordinate efforts, and maybe even a national campaign, will effectively control the problem and rid us of this ‘impatient aggressor’.