Today’s Story from the Museum Floor by Bryony from the Visitor Team is the second part of the post about Himalayan Balsam. Here we look at how best to get rid of this invasive species.
For more information on our Botany collections please see the curator’s blog.
Himalayan Balsam, although it might look pretty, this invasive species has been causing all number of problems for the UK’s wildlife. (Source)
Invasive Species: Oh dear, Oh dear!
Invasive species are those that have not only been introduced to an ecosystem from other ecosystems, but that have found their perfect conditions, much to the detriment of the native species they share that ecosystem with. Introduced species don’t necessarily become invasive – the rabbit, for example, is quite naturalised in the UK, but is actually a species from Southern Europe from where it was brought by the Romans.
See? It looks so innocent, and you’d never suspect a thing… A taxidermy rabbit in our British Wildlife case, Living Worlds, Manchester Museum.
A pretty tough one
Himalayan balsam is maybe the least well-known of the four major invasive plant species present in the UK, but the estimated cost of its eradication would be up to £300 million – a large sum by any reckoning. This is because removing it would be extremely labour-intensive.
Burning it doesn’t work, as its thick stems suck up and retain large amounts water from its surrounding environment, making them essentially fireproof.
Herbicides are also a bad idea near waterways – anything that would kill Himalayan balsam would kill many other things, and would easily get washed into the river when it rained. It is still possible to control it this way of course – the UK Environment Agency tightly controls who is allowed to do this and which pesticides can be used, so permission must always be obtained from them before anything could happen – but the usual herbicide methods such as spraying carry a particularly high risk of spreading to the water. There are other ways to apply herbicides that reduce this risk, such as injecting it directly into the stem of each balsam plant, but as you might imagine, this is both time-consuming and expensive.
A Japanese knotweed having its stem injected – this can only be done by someone with a license to handle herbicides. (Source)
There is research currently being done into the possibility of using a rust fungus from the Himalayas (with the scientific name Puccinia komarovii) that might target Himalayan balsam, as a method of biological control. However, as we’ve seen on this blog before, once a new species is introduced, even to solve a problem, you need to be very careful that it won’t cause a problem for anything else before you set it loose (see ‘War of the Snails’, Round One, Two and Three). After all, at least we can see balsam easily – a fungus, once loose, would be much harder to track and stop. Research on this method began in 2006, and is still ongoing.
It is quite a three pipe problem…
So what alternative does that leave us? Well, you’ve been given a clue to this already in the previous post – did you pick up on it?
This picture also shows the thick, watery stems that make it so hard to get rid of. (source)
Due to its shallow root system, it is very easy to simply pull up and out of the ground. This is known as ‘balsam-bashing’, and is the only current effective method to combat this species. This means people pulling each plant up by hand, but it’s surprisingly easy (you can pull out a six-foot plant one-handed). Concerted efforts – making sure to get all the balsam up every year before they have time to flower and seed – can clear an area of its balsam in just three years.
Himalayan balsam from Surrey. Nature’s Library, Manchester Museum
And that’s why we have a specimen on display in the Museum. Next time you’re passing by a river, or passing by this case on Nature’s Library, remember that the history of this little plant is more than what it seems!
Bryony Rigby
Find out more:
The Economic Cost of Invasive Species on Great Britain
Biological control of Himalayan balsam
Stories from the Museum Floor 