Himalayan Balsam in Europe

Abstract

The Himalayan balsam is a tall, annual, late-blooming plant. It forms dense stands in favorable environs, mostly riverbanks. It’s seen as a troublesome invader in many countries as it’s claimed to outcompete native plants and lure pollinators away from them. Some of those claims are critically reviewed in the chapter. In some European countries such as the UK and the Czech Republic, the Himalayan balsam has had time to occupy most of the suitable riverbanks. In others, such as Sweden and France, the coverage is still much smaller. Currently, the riverside spread continues practically everywhere—and not at a slow pace—and there is nothing to strongly indicate that this trend would soon be broken. Thus, one has to postulate that suitable habitats along more or less all rivers will eventually be invaded. Once a specific site is colonized, however, it need not be so for long. As the river Ruhr case shows, the dynamic of these habitats may make for rapid shifts in dominating species. In other cases, such as the Swedish Suseån, Himalayan balsam stands can be permanent features on a timescale of almost a century.