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With other volunteers I recently spent a day “balsam-bashing” in a local nature reserve. We were trying to control the invasive Himalayan balsam (Impatiens glandulifera).
The event had been organised by Thames21, a charity that works with communities across Greater London to improve the city’s rivers, canals, ponds and lakes for people and wildlife.
Himalayan balsam is a pernicious garden escapee that has become widely established alongside Britain’s waterways, where it chokes most native plants — apart from stinging nettles, which seem to thrive in its company.
The plant is an annual that can reach a height of 2m or more. After flowering between June and October, it forms seed pods, up to 3cm long, which when ripe will dehisce when disturbed, or when exposed to hot sunshine, hurling their seeds up to 7m away.
The best way to eliminate the plant is to pull it up by the roots, which is usually easy when the soil is moist after a period of rain. Alternatively, the plants can be chopped down before they start to spread their seeds.
The plant’s means of seed dispersal is the origin of the generic name Impatiens, meaning “impatient”. Because of this supposed characteristic, the plant has been used in Bach Flower Remedies, where it is prescribed for impetuosity, irritability and extreme mental tension. It is also one of the five ingredients of the Bach “rescue remedy”, promoted for use in traumatic situations such as stress, emergencies and the receipt of bad news, or to “restore mental balance” before an examination or a job interview.
Himalayan balsam has culinary uses too. Its young leaves and shoots, its pink petals, its green seed pods and its seeds are all edible. The raw seeds are said to taste like hazelnuts.
It has been suggested that an effective way to control the plant might be to encourage people to harvest it as a food product before it can spread its seeds.