Well, according to the FT Magazine article, Defining Moment – Japanese knotweed invades Britain, he was the person responsible for introducing Japanese knotweed to the British Isles, way back on 9 August 1850.
Mind you, he also got up to some fairly dodgy dealings in its native Japan. Perhaps as some sort of atonement he then gave them the piano, but I think he was dead before the magnitude of introducing one of Britain’s most pernicious weeds was realised.