French botanist Patrick Blanc did not, as many people believe, invent the green wall system. This was down to Professor Stanley Hart White, who in 1938 patented a “Vegetation-Bearing Architectonic Structure and System”, using “Botanical Bricks”, which could be built to any height to create an instant landscaping effect on vertical surfaces.
Professor White’s ideas predated those of Patrick Blanc by some 50 years. However, Blanc is credited with being the innovator of the modern irrigated system, in which a nutrient-rich solution is fed to plants embedded in a natural or man-made growing media.
A botanical mind
A world-renowned tropical botanist, Blanc noticed how rain forest species were able to grow perfectly well on vertical surfaces even without being rooted in soil. He suggested that the soil itself is simply a mechanical support; what plants needed for life were the water and dissolved minerals, plus sunlight and carbon dioxide for photosynthesis. In tropical rain forests, where rainwater was constantly available, plants had adapted to grow on tree trunks, rocks and other surfaces above ground.
Blanc set to recreating this environment artificially, using polyamide felt matting as a growing medium, emulating the moss-covered surfaces found in the wild. Other solutions – such as modular systems using natural substrate – have since evolved. However, Blanc’s idea of automated drip-feed irrigation, with a system of pipes delivering nutrient to the substrate, utilising capillary action and gravity within a closed system, is scientifically sound and widely employed.
Typical installation of a vertical modular system
With any vertical garden, the building must be protected against moisture with PVC or similar membrane. A framework goes over this, to which the pre-planted modules are fitted.
The living wall is built from the bottom upwards, incorporating pipework and drainage channels into each module. A mechanical irrigation system automatically feeds water and nutrients from the top downwards, as in nature with the fluid trickling through the channels to the ground, where it is collected and recirculated.
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