When we did our l[url=http://www.blipfoto.com/entry/2051335]itter picking[/url] the other day, the Keep Wales Tidy chap pointed out this plant to us. It is Himalayan balsam, an invasive species. It grows tall, very quickly and has an aggressive seed dispersal technique. Good from an evolutionary perspective but bad from an ecodiversity point of view. So I pull it up whenever I see it, here is a pile that has suffered my wrath.
The [url=http://en.wikipedia.org/wiki/Himalayan_Balsam]wikipedia entry[/url] tells us that it was deliberately introduced into the UK because it was so easy to grow. It was promoted with the marvellous phrase of its “”splendid invasiveness”.