The world has more than 380,000 plant species. Scientists working on the Plants Under Pressure project discovered that 1 in 5 is at risk of extinction.
Watch the video to find out what their research revealed about threatened plants and where the extinction hotspots are.
Natural History Museum plant expert Neil Brummitt explains how the research relied on the extensive historical plant collections at the Museum and the Royal Botanic Gardens, Kew.
Their results will help experts monitor the status of plants over time and try to reduce the loss of the planet's biodiversity.