Impatiens glandulifera a.k.a. Policeman's Helmet, Poor Man's Orchid, bee-bums
Himalayan Balsam, or Indian Balsam, is a species on the run! Victorian flower collectors introduced this attractive plant into the Britain from the Himalayas in 1839. It has since escaped the garden and now threatens many natural wetland habitats where it competes with native plants for pollinators and its vigorous growth chokes that of smaller natural species. It is now common all over the British Isles, many parts of temperate Europe and the USA.
Himalayan Balsam is an annual plant, growing up to 2m high and bears many large white, pink or purple flowers from July to October. The stems are deep red, the leaves dark green and serrated, and the flowers are hooded, somewhat orchid-like and shaped like an old fashioned British Bobby's hat, hence one of the other common names, the Policeman's Helmet. One can easily see why the Victorians loved it so much! (Incidently, the colloquial name bee-bums somes from the fact that there are almost always the one or more bees' nether regions poking out of the flowers. The flowers are much richer in sugary nectar than all the natural species, so the bees are more attracted there than elswhere)
Although the plant dies usually within a year, each one is easily capable of producing well over 2000 seeds, which spread with ease down waterways, rivers and ditches, and can take root even under water. Belonging to the impatiens family, the seed pods, when ripe, dehisce scattering the seeds far and wide - it can be great fun to gently touch a ripe pod and watch as it explode, turning itself inside out flinging the seeds as it goes.
Paradoxically, the natural vigour of the Himalayan Balsam may lead to its own downfall. It is much maligned by conservationists, and working parties are regularly sent out to remove as much of it as possible from open countryside. It will remain a popular garden plant, however, so it is unlikely that it will ever become endangered.
I'm trying to establish whether the gorgeous heavy perfume I smelled one August night was in fact coming from this plant, or something else hidden away in a garden. My research has so far drawn a blank. Anyone?