The tree of heaven, Ailanthus altissima, is considered a neophyte in Switzerland, a species recently introduced to the region. However, it is difficult to combat because it is very persistent. Poor soil, drought or even road salt have little effect on it. Air pollution is not a problem either. And it looks pretty. This is why the tree of heaven was introduced to Europe from China as an ornamental plant in the 18th century. Today, however, the tree, which can grow up to 30 metres tall, is considered an invasive species. Young trees of heaven grow quickly – two to three metres a year – and spread rapidly. The winged seeds of the female trees are carried away by the wind. The downside: the undemanding trees displace native species. Another problem, particularly in cities and along roads, is that the fast-growing shoots cause damage to squares and other buildings. Contact with the bark or leaves can cause skin irritation, while the pollen can trigger allergic reactions. In Ticino ...
