From Der Spiegel:
The Vertical Forest, two towers currently under construction in Italy's second-largest city, won't be the modern standard of urban housing, characterized by concrete, steel and glass. Instead, the residential buildings in the central Isola district will be covered in vegetation -- 730 trees, 5,000 shrubs and 11,000 plants, to be exact.
... In addition to being pleasant to behold, the two towers will help purify the city air, increase bio-diversity and protect residents from the sun and noise pollution, they say. At 80 meters and 112 meters (262 feet and 367 feet) tall, they are also an "anti-sprawl measure."
According to Boeri Studio, the vegetation on the buildings will be equal to a hectare of forest, serving as an "ecology billboard."
... Once the project is finished later this year, they will be watered mainly with gray water produced by residents, and tree care will be managed by building staff at the towers, which are part of a larger urban renewal and development project called Porta Nuova.