Once upon a time…
Lizzie was an old and dear friend. One day she introduced me to Laya, one of her close relatives from India. Laya was very nice – tall and elegant and in many ways very similar to dear old Lizzie. When Laya mentioned that she was looking for somewhere to stay I offered her my spare room. All seemed well until I discovered that Laya had spread her stuff into the living room, then the bathroom and then the kitchen. Just when I thought that I should probably do something about it Laya brought in the rest of her family – and there were literally thousands of them. All tall, all elegant and all determined to kick me out of my own house. Before long they had taken over the garden, the house next door and the house next door to that. Then the entire street disappeared and everyone in it. Even dear friend Lizzie doesn’t seem to be answering her phone these days.
That is the story of Himalayan Balsam (Impatiens glandulifera) A.K.A The Policeman’s Helmet, Indian Touch-Me-Not, Pink Peril, Poor Man’s Orchid or Ornamental Jewelweed.
This tall succulent annual was first introduced into Kew Gardens in 1839 as a greenhouse plant. As a taller cousin of the bedding plant Impatiens, our familiar friend “Busy Lizzy”, nobody thought much of Himalayan Balsam – until it escaped into the wild. There this attractive and willowy stranger revealed her true colours – as a rampant bruiser.
Preferring moist sites Himalayan Balsam has now spread itself along river banks, canals and ditches including, without any doubt, one very near you. It works by crowding out and effectively suffocating other plants. An extensive stand of Himalayan Balsam may reduce species richness by 25%. When it dies off in the winter the riverbanks that it once occupied are left bare and vulnerable to erosion. Himalayan Balsam also produces vast amounts of nectar which bees seem to prefer to the home-grown variety, severely reducing the pollination of our own indigenous plants. Laya also carries a blunderbuss. In the autumn, about 12-14 weeks after flowering, Himalayan Balsam spreads vast quantities of seeds – up to 800 from a single plant – by firing them from seed capsules up to 7 metres from the mother plant. The name ‘impatiens’ comes from this ‘impatient’ release of seeds.
Conservation groups like the National Trust, British Waterways and the Environment Agency have declared war on tall and elegant Laya. Local groups too, like the Cole Park Allotments Association and the Tidal Crane Association, have held bouts of “Balsam Bashing” this year. Although Himalayan Balsam can be killed by weedkillers like Glyphosate the preferred method is to grab hold of the plant at ground level below the lowest node and pull it up. Then compost it or just leave it lying on the ground away from any running water until it rots down. Do not be tempted to throw the stems into rivers or ditches. The seeds can survive up to 2 years and will just take root elsewhere. The most important thing is to do this before the balsam has set seed. If you try to exterminate this most invasive of plants after seed set all you will be doing is making trouble for yourself – and the people next door – and the people next door to them – and the people next door to them…
As well as producing a natural yellow dye the stems of Himalayan Balsam can be eaten after boiling. Encouraged by this – and a relaxed “Eat your Enemy” policy – the Bionic Control of Invasive Weeds Laboratory in Wiesbaden, Germany is setting up a project to conserve local biodiversity by developing food products made from the plant. Eventually, if all goes well, this project will have the Himalayan Balsam financing its own eradication. Another helping of Impatiens, Lizzie?
— from Martyn Day