India, April 26 -- I t's a tall tree that grows fast, is incredibly hardy, and appears to repel insects. Intrigued by these qualities, European explorers took saplings home, starting in the 1700s. The Ailanthus altissima or Tree of Heaven is now among the 10 most widespread invasive alien species worldwide, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). It is more than somewhat unstoppable. It produces hardy winged seeds - as many as 325,000 per mature tree annually - and can also reproduce asexually by cloning itself via a powerful root-sucker system. In this way, it forms dense thickets. It resprouts vigorously after cutting or a fire. Around the world, it is crowding out native ...