Biological concrete...

'Scientists at a Spanish university are developing a new type of concrete that captures rainwater to create living walls of moss and fungi.

Unlike existing vertical garden systems which require complex supporting structures, the new "biological concrete" supports the growth of organisms on its own surface, according to researchers from Universitat Politècnica de Catalunya in Barcelona.'

http://www.dezeen.com/2013/01/03/spanish-researchers-develop-biological-concrete-for-moss-covered-walls/