Invasive plants spread fast in billion-dollar threat - study

The invaders include water hyacinth from the Amazon, which has spread to about 50 nations where it crowds out local plants, while Japanese knotweed has fast-growing roots that have destabilised buildings in North America and Europe. The spread of alien plants was likely to increase with rising trade and travel by emerging nations led by China, it said. "North America has had most – many came from Europe after Columbus because colonists brought plants with them," lead author Mark van Kleune