Since it was introduced to the UK in 1850, Japanese knotweed has gone from novel ornamental plant to rampant invasive species. Madeleine Finlay speaks to journalist Samanth Subramanian about the huge costs associated with finding it on a property, and Dr Sophie Hocking explains what the plant, and our attempts to control it, might be doing to the environment.. Help support our independent journalism at theguardian.com/sciencepod