Invasive Aliens

24 July 2020

At this time of the year we usually try to take care of some of the unwanted green invaders. Giant Hogweed and Himalayan Balsam.

Giant Hogweed was introduced to Britain in the 19th Century and proved to be very invasive along riverbanks and water crossings. With a height of 2-5 metres, a mature plant is easily recognisable with bright green stems and an extensive dark reddish-purple splotches and prominent course white hairs. The flowers are displayed white in an umbrella shape, around 100cm in diameter across the flat top. The seeds are produced in vast numbers, 10k-50k per plant during the summer, and can remain alive in the seed bank for up to five years. This plant is phototoxic and if a person touches or is touched by this plant on bare skin it can result in painful blisters and scares. This serious reaction is due to the sap contained in the leaves, roots, stems, seeds and the flowers of the plant.

The second plant we are tackling is the Himalayan Balsam. Again, introduced into gardens in the 19th Century this plant survives extremely well on wet ground surrounding riverbanks. Unlike the giant Hogweed you can remove the Balsam by removing the roots by wearing gloves. Up to two metres in height with a soft green or red tinged stem, the Balsam has pink flowers in the shape of a hood that can be three to four centimetres tall and two centimetres broad. The plant forms seedpods that explode when disturbed, scattering seeds up to seven metres. Easily breakable, the plant will produce a large distinctive pop if not pulled all the way to the roots. Recipes do exist to turn the flower of the Himalayan Balsam into jams and parfaits, but for once I will leave this to the much more adventurous wild gatherer.

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