Invaders From......

.... Paddling down the R.Tees near Newsham we came across this tropical rain forest.  Alas, it consists of mainly three introduced species and non of them from the tropics

:-

Giant Hogweed, from Southern Russian/Caucasus
Japanese Knotweed, from errrr??? Japan!
Himalayan Balsam, from ????  Oh, yes - the Himalayan mountains.

All three species spread easily down rivers and in some areas, such as this on the Tees forms dense stands eliminating all native species.