it's actuallmore natural than with soil.
the selection of plants is bassed on several factors:
1.what's the local clymates
2.how much sun exposure the surface.
3.is there any particular micro clymates?
4.such as high buildings creating strong wind along wall
the concept of it dates back to 600BC with the hanging garden of babylon.
the larger vertical garden concept has been utilized with innovative hidroponic tecnology.
There are two main categories of green walls: green façades and living walls. Green façades are made up of climbing plants either growing directly on a wall or, more recently, specially designed supporting structures. The plant shoot system grows up the side of the building while being rooted in the ground. With a living wall the modular panels are often made of stainless steel containers, geotextiles, irrigation systems, a growing medium and vegetation.
There are three types of growth media used in living walls: loose mat,mat media ,and structural media.