A green wall is a vertical built structure intentionally covered by vegetation. Green walls include a vertically applied growth medium such as soil, substitute substrate, or hydroculture felt; as well as an integrated hydration and fertigation delivery system. They are also referred to as living walls or vertical gardens, and widely associated with the delivery of many beneficial ecosystem services.Green walls differ from the more established vertical greening typology of 'green facades' as they have the growth medium supported on the vertical face of the host wall (as described below), while green facades have the growth medium only at the base (either in a container or as a ground bed). Green facades typically support climbing plants that climb up the vertical face of the host wall, while green walls can accommodate a variety of plant species. Green walls may be implanted indoors or outdoors; as freestanding installations or attached to existing host walls; and applied in a variety of sizes.
Stanley Hart White, a Professor of Landscape Architecture at the University of Illinois from 1922 to 1959, patented a 'vegetation-Bearing Architectonic Structure and System' in 1938, though his invention did not progress beyond prototypes in his backyard in Urbana, Illinois. The popularising of green walls is often credited to Patrick Blanc, a French botanist specialised in tropical forest undergrowth. He worked with architect Adrien Fainsilber and engineer Peter Rice to implement the first successful large indoor green wall or Mur Vegetal in 1986 at the Cité des Sciences et de l'Industrie in Paris, and has since been involved with the design and implementation of a number of notable installations (e.g.