Phillipp Franz Balthasar von Siebold, the physician and botanist, bought Japanese knotweed to Europe. Von Siebold travelled across Japan for 8 years before returning to Europe, bringing hundreds of samples with him, including Japanese knotweed. A specimen was donated to the Botanic Gardens in Kew in 1850 and from there, the plant has spread. Japanese knotweed is now found UK wide, with the weed spreading thanks to the rail and water networks. Also, Japanese knotweed is also found in Ireland, with the first record of the plant found in the country in 1872.
Japanese knotweed is still most prevalent in the UK, due to the plant’s popularity in the late Victorian era in themed gardens.