Generally in architecture when someone refers to a building as ‘green’ they are referring to the fact that the buildings are built with environmental requirements and the conservation of energy in mind. In this recent WSJ article by Ken Wells he talk about structures that are green in a different way. A biophilic way.
Biophilia as defined by Merriam-Webster is “a hypothetical human tendency to interact or be closely associated with other forms of life in nature”. So when it comes to architectural and interior design it refers to incorporating or surrounding the structures with greenery/nature. Bringing the outdoors indoors. This way of designing can have a advantageous results in energy savings and the general beautiful aesthetic it brings to the design of the building and interior.
A simple google search of “vertical forest” will yield results of the Bosco Verticale building (which translates to Vertical Forest) in Milan and structures similar to it.