Imagine a summer stroll along a local riverbank or footbath. With councils cutting back on maintenance, things are lusher and wilder than ever: you might spot oversized leaves topped with plumes of creamy blooms, intricate purple blossom with an appley scent, or giant towering lacy white flowers. Idyllic, no? Well, that’s Japanese knotweed, Himalayan balsam and giant hogweed, three of the UK’s worst invasive species. Every summer brings fresh horror stories about these biodiversity-bashing bullies, especially knotweed: “I don’t feel very safe near it,” a Croydon woman whose garden is overrun said recently; homeowners in Llanelli are watching, helpless, as a forest of knotweed creeps ever closer.
How worried should we be? From the tens of thousands of non-native species grown in British gardens, only a tiny proportion escape to become invasive. Yet the expression “Invasive non-natives” has a sort of… Farage-y quality. Alien plants, coming over here, taking our nutrients, confusing our pollinators and destroying our biodiversity? It’s the stuff of nightmares: time to take back control. The truth, predictably, is less alarmist. Alastair Fitter, plant ecologist and author of The Wild Flowers of Britain and Ireland, explains, “Any time you bring in a new garden plant, you’re running a roughly 1/1000 chance of it becoming a pest.” Moreover, most pollinators don’t care what they pollinate, and non-natives add colour and beauty to our environment: “There are lots of non-native plants people admire: we rather like having meadows of fritillaries.”
