Himalayan Balsam (Impatiens glandulifera) is known to many people as an attractive plant with a familiar sweet scent, and a reputation for being a good nectar source for bees. However, despite the plant being valued for these reasons, Himalayan Balsam is actually one of the most problematic weed plants that we have in the UK.
It is a non-native species that was taken from its natural home in the Western Himalayas and was brought to the UK in 1839 to look pretty in our gardens. It goes by the different names of Kiss-me-on-the-mountain, Indian Balsam and Policeman’s Helmet, amongst others, but is distinctive in its appearance, having pinkish flowers, oblong jagged-edged leaves and a pink tinged succulent stem.
The green seed pods are also quite unique, holding up to 16 seeds each, which they can fling up to 7 metres away when touched. One Himalayan Balsam plant is said to be able to spread 2,500 seeds alone!
It is no surprise that it has spread so successfully and is now common all over the UK. None of our native wildlife eats enough Balsam to be able to control it in that way and our native wild flowers can’t compete with it.
Himalayan Balsam grows particularly well in damp places, and is commonly found spreading along river banks where it can float its seeds downstream to colonise new areas. It grows up to 3 metres high, shading out the plants beneath it so that only crowds of tall Balsam are left growing. When these die out in the autumn, the ground is left bare and vulnerable to erosion.
In the UK it is illegal to plant Himalayan Balsam in the wild or to allow it to spread into the wild. The plant can be eradicated by licenced practitioners using chemical control in certain places, but this is limited to places that are not near rivers, where Balsam often grows. This method may also result in non-target plants being killed.
Cutting the Himalayan Balsam below the lowest node of the plant is also an option, but mostly Balsam is pulled from the ground by hand. This manual method is easy because the plants have shallow roots, but this is very time consuming and needs to be done in the small window of time from when they first come up, to before they start to flower.
To stop Himalayan Balsam’s prolific spread there needs to be catchment scale, widespread control, which needs to be repeated in order that seeds in the seed bank cannot just repopulate the areas that have been cleared. The seeds only survive for up to 18 months so it is estimated that Himalayan Balsam can be removed completely from an area within 2 years if repeated control efforts are made and there is no re-introduction of the plant from nearby sites.
Traditional methods are inadequate for stopping the spread of Himalayan Balsam in the UK. Using the methods we currently have, the Environment Agency has estimated the cost of eradication of Himalayan Balsam from the UK would be around £300 million. DEFRA is now considering release of a rust fungus (Puccinia komarovii var. glandulifera) which has been shown to weaken Himalayan Balsam and reduce its competitive advantage. There is certainly a chance that this bio-control method could help to reduce spread of Balsam; however, if the decision is made to release the rust fungi then it would be irreversible.
To eradicate the Himalayan Balsam from our Nature Reserves the Wildlife Trust of South and West Wales has been holding annual ‘Balsam Bashes’ with groups of volunteers to manually remove the plants from the ground. At the moment, this is the best defence we have against the spread of Balsam, so it is vital work if we want to continue to see our native wildflowers in bloom. Hopefully the future holds a better solution for controlling this invasive plant in the UK, but for now, we need all the help we can get.
Visit our events page to learn more about volunteering on our Friday Balsam Bashes at Parc Slip, or email Lorna Baggett on email@example.com to find out other ways to help.