Outside green walls – an introduction
Vertical gardens or green walls describe are artificial ecosystems, designed either as aesthetic elements, as part of a so-called urban gardening, sometimes as works of art using the plants or with specific intention of retaining sound or regulate heat.
In the latter case, these walls, such as vegetated terraces or fences, helps to improve the characteristics of a building, and perhaps to restore green areas, particularly in the city.
They can serve as a refuge for birds, insects, but they can also play a role in the microclimate, water purification, sound control and urban air quality. Its horizontal equivalent is a green roof.
History of the vertical garden
Natural colonization by plants on walls is usually considered a problem, the roots damaging the foundations of the building when they are wet. This, under certain conditions, can take off the bricks or contribute moisture to the wall. In the humid areas, some trees can quickly colonize and cover architectures -such as for example the temples in Thailand.
There are some artificial architectural structures, concrete or stone masonry units covered with moss and plants that have existed for over 200 years. These are mainly found in a few large parks typically surrounded with fountains or waterfalls.
This construction is especially found in French gardens in the nineteenth century.
Green walls were then developed in some zoos, and for the set of terrariums, generally using tropical species. This is before the French botanist and scientist Patrick Blanc created, tested and developed his concept of green wall.
Some other techniques of walls where plants grow independently, were developed by designers and landscape architects as new methods for interior spaces.
For instance, Fedor van der Valk has invented mini indoor hanging garden (“String Gardens”) that seem to float in the air supporting cascades of greenery. The New Zealand Patrick Morris was able to give the impression that the ceiling is covered with plants. Many examples of interior walls are now available.
Several Principles of green wall
Green walls or vertical garden can be arranged both outside and inside buildings, with or without artificial source of light.
The principle relies on the fact that without human intervention, in the presence of clean air and sufficient moisture in the air, plants will develop by themselves. In the case where the wall is dry, or a drier atmosphere, it can also be colonized by vines and ivies
Several approaches exist, from the insertion of plants adapted to dry environments which create a structure like a “rock garden” to very sophisticated techniques optimizing the colonization and growth of plants with substrates capable of absorbing and releasing water like coconut fibers.
Or with plastic in which water circulates enriched with nutrients.
In the latter two cases, irrigation works in a closed circuit, and must be adapted to the context and seasonal climate, the watering system is more or less automated depending on the case, as well as the nutrient. An automatic watering systems is one of the core elements of your vertical garden or green wall.
Many tropical plants grow in the shade and need few nutrients, but require soft, pure water (eg rainwater).