Known by several names including green walls, living walls, or vertical gardens, these architectural elements can be found on exteriors or interiors of buildings, and can range in size from just a few square feet to entire walls in atrium spaces. They were first developed by Stanley Hart White, a professor of landscape architecture at the University of Illinois, in 1938; he created a patent for his "vegetation-bearing architectonic structure and system," but the invention didn’t really take off.
The Rise of the Vertical Garden
Fast forward about seven or eight decades, and living walls are some of the most popular, vibrant ways to incorporate plants and greenery indoors and out, often in aesthetically pleasing ways. A green wall is essentially a wall, or part of a wall, that is covered with greenery growing in soil or another type of substrate. Most living walls also incorporate an integrated water delivery system because the classic method of watering plants with a watering can or hose isn’t efficient for vertical walls.
When used on the exterior of buildings, vertical gardens are most frequently found in cities, where the plants act as an additional layer of insulation and help reduce the overall temperatures of the building from solar radiation or prevent warm air from leaving the building. Some research has also shown that living walls may help purify gray water, or gently used water from bathroom sinks, showers, tubs, and washing machines.
When vertical gardens are used on the interiors of buildings, they can help improve air quality not only because plants naturally remove carbon dioxide and produce oxygen-rich air, but also because plants can filter the air around them by absorbing and cleaning pollutants. When they’re used inside, living green walls frequently act as a three-dimensional, living piece of artwork, providing an aesthetic component as well as a health element.
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How to Plant a Living Wall
Living walls are typically constructed similar to green roofs, where modular panels hold the growing medium that can be either loose soil, mat media, or structural media.
In order to create a living wall with loose media, loose soil is poured onto a shelf or into a bag, which is then attached to the wall. While these systems can be straightforward to install, the media must be replaced at least once a year for exterior installations and every two years for interior uses because wind and rain can drain or blow away the soil. Because of this, loose media systems are probably best for small-scale living walls or home gardeners.
Mat media systems are usually composed of thin-coir fiber or felt mats of multiple layers which are best for interior use and with smaller plants. Because the mats, despite their layers, are not very sturdy, they cannot support larger plants with thicker, longer roots that could potentially rip the mats and compromise their integrity. Although these mat systems are easy to install, the thinness of the mat makes them unable to hold much water, and therefore they aren’t very water-efficient. However, for smaller installations with smaller plants, they can be a great solution.
For sheet media systems, the living wall is made of an egg crate-type of pattern on a plastic sheet that can be used for both outdoor roof gardens and vertical walls. Because of the added depth and texture of the sheet media systems, they are able to hold significantly more water than the mat media system, and can last up to 20 years because the plastic isn’t biodegradable.
Finally, living green walls that use structural media employ a type of block of soil or growing media that can vary in size, shape, and thickness. Because of the flexibility in the dimensions and shapes of the blocks, the media can be specifically designed to accommodate certain types of plants that require thicker or thinner media. Another advantage to structural media living walls are their long life—they can last up to 10 to 15 years before needing to be replaced or repaired.