From The Himalayas To Here: Part 1 – Himalayan Balsam

Today is International Museums Day, and this is quite a fitting celebration for Manchester Museum. The objects in our collection come from all over the world and are connected by the very different journeys that they have made to Manchester, as we aim to promote and understanding between cultures and work towards a sustainable world.

Earlier this month, we were delighted to announce our large grant from the Heritage Lotteries Fund, which together with the support from the Treasury and awards and donations by key individuals, Trusts and Foundations will see Manchester Museum undergo a major transformation, opening a South Asia gallery, a new Temporary Exhibitions Gallery and the Dr Lee Kai Hung Chinese Culture Gallery in late 2020.

Today’s post is part of a series focusing Asia, exploring the objects that are currently on display that relate to this fascinating region of the world. 

For more about the ways that Manchester Museum is changing, have a look at the Courtyard Project blog.

From The Himalayas To Here

Himalayan Balsam

Invasive species are those species that have come from a different ecosystem to ours, disrupting our own native ecosystem and affecting our wild flora and fauna. Some examples will be household names to many of us, such as the grey squirrel, Japanese knotweed, and mink, but have you ever seen a sight like this?

Himalayan balsam along river 2Does it look familiar? (Source: Lancashire Invasive Species Project)

Yes, this plant may be very familiar if you’ve ever taken a walk alongside a river in summer, but this is no native species. Its name is Himalayan balsam.

Himalayan balsam (also known as kiss-me-on-the-mountain, or policeman’s helmet, or even Impatiens glandulifera if you are using the proper scientific term) originally came from the Himalayas, a mountain range that has the Tibet region of China on one side, and India and Pakistan on the other.

It’s been here for a long time – it began as a garden plant, first arriving on our shores in 1839, before escaping and spreading to all corners of the UK, particularly alongside water, although there’s evidence that it’s now adapting to drier conditions than it is restricted to in its native range, allowing it to spread even further.

This, of course, initially bought it some favour – it was a popular garden plant for a long time, due to its ability to form verdant clumps almost anywhere, even on poor ground. It started off in the gardens of the wealthy, who could first afford to import plants from far-away lands, but later became a very common plant for all gardeners. It was first recorded growing wild here in 1855.

Explosive Seeds

It also became popular because generations of people have taken great joy in touching the seed pods, which react a little… explosively. When disturbed, these seed pods suddenly open and curl back, flinging the seeds many metres away from the parent plant. Although this is fun to do, the consequences are that around 16 seeds at a time will be dispersed and more plants will grow – it is now actually illegal to propagate these plants in the UK, so watch out if you’re thinking of trying it out! Here’s a video instead:

Seed pods exploding – it moves very quickly, but see if you can see what happens. Of course, particularly along rivers, the seeds often get carried downriver and spread to other areas.

The Main Issues

Of course, this all works well in its native habitat, where there are natural controls on its numbers, whether through creatures eating it; having a fair competition with other plants for pollinators; or being a similar height to many other native species in the habitat, so facing a fair competition for light. Quite simply, it fits in there. But here…

Firstly, although it is eaten by animals like cows, sheep and deer, they don’t particularly favour this plant (they have no evolutionary reason to) and it grows in some difficult-to-reach areas, so they can’t make a significant dent in its numbers.

Secondly, the sickly-sweet smell it gives off is a symptom of one of the issues that makes it both a threat to our native species and such a prolific spreader – its nectar is much, much sweeter than our UK plants. This means pollinating insects love this plant, and will visit it often, ignoring the native plant species that would usually rely on them to produce their seeds.

And thirdly, this plant is also much taller than our native herbaceous plants (it can grow to over two metres in height) so the moment it surpasses our native species and unfurls its leaves, that’s the end for our native plants having any access to sunlight. This means that it can easily form a monoculture, with large areas having no other plant species at all.

Himalayan balsam, with a bee vising the flower, left, and right, an example of a large monoculture of balsam, not an uncommon sight in the UK. This is what it looks like before it flowers, particularly in the spring. (Source: NaturePhoto and Himalayan Balsam)

That isn’t the end to the problems it causes, of course – as well as being a huge problem for our native plants, the monocultures lead to loss of animal species too, as some species (e.g. many butterflies) rely on a specific food plant and they disappear when their plant disappears. Balsam also has a very shallow root system, and when there are no deeper-rooted plants mixed in to hold everything together, soil erosion and riverbank collapse is inevitable.

Phew! That’s quite a few problems for one little plant. But what can we do about it?

Stay tuned for the next instalment to find out…

Bryony Rigby

P.S. Want to find out more?
https://commonbynature.co.uk/2016/07/11/a-spotlight-on-himalayan-balsam/
https://www.cabi.org/projects/project?pid=32944
https://www.welshwildlife.org/wildlifeblog/himalayan-balsam-problems-brought/

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