India, April 26 -- A perennial plant with small, cream flowers, native to Japan, China and Korea, it looks harmless enough. Yet the Japanese knotweed is currently devaluing land and property in the UK and Ireland. It is also rampant in parts of Europe, New Zealand and North America. It was introduced on these continents in the 19th century, as an ornamental plant and because it had proven effective in fortifying embankments and preventing erosion. Botanists were fascinated by its ability to withstand high temperatures and drought, thrive in different soil types and amid salinity. They studied its breeding patterns, hardy seeds and hardier roots. These have since invaded building foundations, walls, drains, roads, pavements and retaining wal...