The Victorians' pride at the effortless movement of plants around the world during the late 19th century was having an unwelcome side effect. Invasive species were beginning to wipe out native populations of plants. With no natural predators to control them, one man's flower was turning into another man's weed. Prof Kathy Willis hears how during the late 1800s, many invasive species from Japanese knot weed to Himalayan balsam to water hyacinth came from deliberate introductions and asks if today, trying to control them is ultimately futile? As historian Jim Endersby explains both Charles Darwin and Kew's director Joseph Hooker were the first to examine the impact of invasives, having noticed on the island of St Helena and Ascension Island the effect on native plants. One of the current biggest invaders is lantana, familiar to British gardeners as a small pot plant. As Shonil Baghwat of the Open University reveals, since its introduction to Kolkata Botanical garden in the 1870s it decimated native teak plantations. But today opportunities exist to exploit its presence for the wood, basketry and paper industries. And Kathy Willis hears from Kew conservationist Colin Clubbe on the extent to which we should view invasive plants in our ecosystems as part of a strategy to maintain resilience to environmental change in the future. Producer Adrian Washbourne.