exotic

(alien)  Describing  an  organism that has originated from another region and is not native to the area in question.   The   term   is   used   especially   of tropical plants grown in greenhouses or indoors in temperate regions. An exotic plant  that has  become  adapted  to  its new environment and can grow successfully without help from man is termed naturalized.  An example in the UK is the  monkey  flower  (Mimulus guttatus), which  originated from North  America. Many naturalized plants are garden escapes.