Know your foreign invaders
Rhododendron can get out of hand and become invasive
Alien plants regularly make headlines, when their possible threat to our native plants or to the wider environment makes alarming news.
An alien plant is one that occurs naturally elsewhere. There have been countless introductions of aliens into our gardens over the centuries. It’s estimated that a mere 1,500 plants are â– trulynativetoBritain, whereas as many as 26,000 species from elsewhere grow here, and our gardens would be
impoverished without them.
The crucial factor is whether the alien is well-behaved or likely to become an invasive menace in theUK. The pretty little azolla fern, for example, once a popular garden pond plant and widely farmed as a protein source and nutrient in paddy fields, has escaped into the wild, choking ponds and other water courses and competing ruthlessly with native plants.
It is now classified in the UK as an unwelcome alien, its sale discouraged under various Codes of Practice, together with other invasive marginal and aquatic plants including
Himalayan balsam, floating pennywort and water primrose. Japanese knotweed is even less welcome: its release into the wild is an offence, and plants need secure disposal as controlled waste at registered council sites.
Rhododendron ponticum, Spanish bluebells and buddleias are all lovely plants that may become foreign invaders in the wider environment, potentially dominating important ecosystems. The remedy is not for gardeners to abandon growing aliens, but to simply limit their spread and escape into the wild.