Plant walls, also known as green walls, vertical gardens, green facades or living walls are structures that allow for vertical plant growth on structures like walls or trellises. These can be found in various spaces, including commercial buildings, residences and public areas. Vertical gardens can be found in both interior and exterior environments. Based on the project’s design requirements, different systems can be used to set up a plant wall. Besides the aesthetic appeal they provide, green walls also come with many benefits, particularly for those that inhabit the surrounding space.
A history of green walls
While often thought of as a modern system, the first plant walls were likely the hanging gardens of Ancient Babylon, in present-day Iraq. Historical records show that King Nebuchadnezzar II had them built for his wife in 600 B.C.E. Spring water flowed from the top of the palace walls and trickled down into the many terrace gardens, keeping the plants lush and flowering. This palace is likely to have been the first building with an in-built irrigation system.
The development of modern green wall systems is credited to Stanley Hart White, a landscape architecture professor at the University of Illinois. In the 1930s, he tested various prototypes of green wall systems in his backyard. Later on, in 1938, he patented his system under the name “Botanical Bricks.” These were modular plant units that could be stacked up to great heights. In 1988, the invention was popularized by French botanist Patrick Blanc. Blanc set up a vertical garden at the Paris Museum of Science and Industry, which brought this concept to the public.
How do green walls work?
Most living walls fall under one of three categories. These are panel or modular systems, felt systems and trellis systems. Designers will opt for one of these solutions based on a project’s location, scale, vertical structure and purpose.
Panels, modules or trays
These systems use wall panels or trays with pre-planted or prepped vegetation. This is usually grown in a nursery first and then incorporated into the panels before the installation onto an existing wall or prefabricated vertical structure. Hence, the method allows for lush, fully-grown plants to be installed on the wall, as opposed to them growing on-site over some time.
Once installed, this system is typically the easiest to maintain. This is because if plants in one unit start to wilt or become sick, that specific module or tray can be swapped out for another one with healthier vegetation, without disrupting the entire system. Additionally, for resource-conserving irrigation, vegetation can be watered through greywater pipes that run behind the panels, which helps cut down costs and conserves fresh water.
Panel systems are useful because they can be installed in both indoor and outdoor environments. They also work well irrespective of the climate and vegetation can be carefully selected to meet various design and site-specific needs. In fact, panels can feature a diversified plant palette, allowing vegetation with differing growth needs, such as water level and growing medium, to grow in a single space. Further, these qualities make them useful for brand statements and custom designs.
These green walls are similar to panel systems, except these wall panels have felt pockets that can be filled with growing medium. Seedlings from a nursery are then replanted into these pockets, which grow to form part of the larger system. Oftentimes, these types of plant walls are watered using an irrigation system that is built into the wall. This ensures that the plants remain hydrated by absorbing moisture that is distributed into the felt pockets.
Similar to the modular units, maintenance can be relatively easy. This is because maintenance is localized and can easily be done by swapping out plants or felt pocket panels that need to be changed.
This system is most commonly used in exterior environments and is often projected off a wall or vertical surface. A secondary structure, typically a lattice made from metal or wood, is set up to serve as a framework for vegetation. Then, plants rooted in the ground or pots grow upwards and attach themselves to this vertical framework. Through their growth, the vegetation climbs upwards to fill up the gaps within the latticed structure of the trellis, creating a thick, hedge-like form of greenery.
Trellis systems can be more challenging to maintain. They often require external irrigation systems that are not integrated into their structural frame. Furthermore, as the plants grow, they need extra pruning and care to prevent overgrowth. This can make them hard to manage over time, as they become more densely woven into the “fabric” of the trellis.
What are the benefits of green walls?
Like any biophilic design feature, living walls have several benefits for those in the vicinity. Besides creating a visually-appealing environment, plant walls can have very practical and tangible effects on the surroundings.
One of the key benefits is that green walls create their own microclimate. This is a multi-faceted component, as these microclimates regulate temperatures and serve as a space that small plants, animals and other organisms can inhabit. By creating a microclimate, plant walls are excellent at improving biodiversity outdoors. They are also useful for reducing interior and exterior temperatures and creating temperature differences of several degrees.
For green facades, the plants prevent building surfaces from absorbing and re-radiating solar energy into the surroundings. Doing this helps mitigate the urban heat island effect. This means that cities, which are typically warmer than suburban and rural areas, can benefit from these microclimates, which regulate temperatures and create hubs for living creatures to thrive.
In addition to creating microclimates, green walls are excellent at boosting health and well-being. Currently, one of the most significant health-threatening concerns is the dangerous levels of pollutants and microparticles in urban environments. To combat this, plants are excellent at capturing these toxins through natural processes and cleaning the air we breathe. Additionally, biophilic design features like green walls have been shown to improve overall health and well-being, especially by lowering stress levels, boosting moods and enhancing mental well-being.
Alongside improving physical and psychological health, green infrastructure is beneficial for creating conducive living and working environments. The biophilic qualities have been shown to boost productivity and creativity. Meanwhile, the natural cushioning properties of the plants help dampen sounds for a more peaceful environment.
Biophilia is the key for future designs
Through these aforementioned benefits, it can be understood that biophilia is a key design strategy to support the health and well-being of living organisms in cities. By incorporating green infrastructure like green walls into urban and architectural designs, the aesthetic possibilities and socio-environmental benefits are endless.
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