It used to be customary in Japan to plant a paulowna tree – or kiri tree, as they're known in Japanese – after the birth of a daughter. When the girl grew up and got married, the tree, which in that time had reached a very large height, was chopped down and used to make cupboards and trunks to store the brides many silk kimonos.

These days tree-planting space in Japan is at a premium, but in Europe there is plenty of room. Now two graduate students from the University of Bonn want to plant their own kiri trees on large plantations in Germany and the rest of the EU. They've created a company called We-grow, and are hoping to lure investors with the promise of money that, quite literally, will be growing on trees.