Himalayan balsam: the weed used in Hertfordshire gin
PUBLISHED: 10:42 07 August 2018 | UPDATED: 16:59 07 August 2018
How to tackle one of the most invasive plant species in the UK has resulted in innovative solutions, writes Charlotte Hussey of Herts and Middlesex Wildlife Trust
Himalayan balsam, a relative of the busy Lizzie, was introduced to Britain as a garden plant in the 19th century. Prized for its signature drooping pink flowers, this prolific plant soon escaped the confines of the Victorian garden and is now causing serious conservation problems.
It grows quickly between May and August and can reach heights of up to 10ft. By late summer explosive pods have developed, which can fire seeds up to 22ft away. Seeds are also spread easily along waterways and this has resulted in Himalayan balsam becoming widely naturalised along riverbanks. This is especially problematic as it invades wet habitat quickly at the expense of other, native flowers that are crowded out and unable to access essential sunlight and soil nutrients. When the balsam dies back over winter, it leaves river banks bare and vulnerable to erosion. This is a critical issue for water voles as they rely on grasses and other bankside plants to feed on during winter and early spring. Heavy infestations of balsam mean there is no bankside food for them.
Over the winter, animals that would usually shelter in our native plants no longer have suitable habitat, and the eroding river banks mean that increased sediment makes its way into rivers, silting the bare gravels in chalk streams and making them unsuitable habitat for fish such as brown trout to lay their eggs.
Controlling Himalayan balsam
To combat this ongoing problem, Herts and Middlesex Wildlife Trust, after checking for breeding birds, coordinates volunteer Himalayan balsam pulling work parties every summer before the seeds develop and spread. The plant is surprisingly easy to pull up and huge areas can be cleared in just a few hours. The plants are typically piled up after they are pulled, where they die before they have a chance to set seed. As Himalayan balsam is so prolific, pulling the plant – or ‘balsam bashing’ as it has become known – needs to be done regularly.
Non-native species arrive in the UK without their natural enemies – insects, plants or animals – that keep each other in check in their native countries. This means that Himalayan balsam has been able to spread and smother other plants with no resistance.
Over the past few years, biological control has been researched by the Centre for Agriculture and Biosciences International. It aims to find something that exclusively attacks the species. In 2010 a rust fungus was observed causing significant impacts on the balsam in the Indian Himalayas.
Following extensive lab testing, the rust fungus has been released on specific sites around the UK, including nearby Middlesex.
The results are encouraging and provide evidence that the fungus is well capable of establishment in the UK. It’s spread and impact will be monitored over the next few years and it will hopefully lead to successful management of this noxious weed.
An unlikely ally
Last year an idea to use the discarded plant from balsam bashing sessions was developed by the trust in partnership with Wilstone-based Puddingstone Distillery, which developed a recipe for a world-first gin that used Himalayan balsam as one of its botanicals.
Distillery owners Ben and Kate Marston used the petals of the balsam to add both flavour and a delicate pink colour to the gin. Puddingstone Distillery donates £2 to the trust for every bottle of the special edition gin sold.
The gin has been a roaring success and after a long wait over winter, it’s back for a limited time. To further improve its green credentials, it now has a fully biodegradable anti-tamper seal.
Get your hands on a bottle at puddingstonedistillery.com