Although the cityscape is where vertical gardens have the most impact, they are not irrelevant in the home garden.
Blanc's vertical garden on the Caixa Forum Museum, Madrid
There’s a fine line between a fad and a shift in the way we do things, and a lot of common ground in between. The green-wall craze is no different, except the real deal requires no ground or even soil. With so many versions on the market, the concept deserves further exploration.
Vertical-wall gardens originated with a 13-year-old Parisian boy with a passion for tropical species. He noticed aquatic plants growing out of his aquarium and began to train them up his bedroom walls. Then he developed different support methods for the plants and their roots as they outgrew the fish tank, pumping water from his aquarium to irrigate what was fast becoming his bedroom jungle.
That boy, Patrick Blanc, is now nearing 60. With flamboyant green hair and eccentrically long fingernails, he is still exploring the limits of this idea with a brilliant flair that has evolved as organically as the walls themselves. The result – a fusion of science, art and nature – is breathtakingly beautiful.
As a schoolboy, he travelled to Malaysia with his parents. Here were the orchids and begonias he had admired at floral exhibitions, but the form and context of these same flowers growing naturally in a forest were an inspiration.
Understanding the origin of plants is critical to the development of the green-wall system. Blanc went on to study botany, gaining a doctorate and critical acclaim for his work with tropical plants, particularly those living in the understorey – where epiphytes grow on trees and ecologies exist on rock formations – and in cracks and crevices that are the environments mimicked by his walls.
He studied plants in Malaysia where, because of the high rainfall, about 2500 of 8000 endemic species can be found growing naturally with no soil. This inspired the basis for the hydroponic nature of the green-wall system.
He also observed that where plants are grown on a surface rather than in a medium, greater biodiversity occurs, as plant size is limited, which in turn limits competition. The size of the plant is limited by the reduced root volume, but not at the expense of its general health or vigour as long as the flow of water and nutrients is consistent. Think of a bonsai.
Increased biodiversity is a key theme in Blanc’s walls and one of the most exciting aspects of his work.
His first green walls were developed at home and for enthusiastic friends. His first public wall was a spiral tower planted on both sides at the Chaumont Garden Festival in 1996, a permanent installation that’s still growing well. This was really the launch of the phenomenon. From here, his work began to spread until it was covering skyscrapers.
Collaborations between architects and other creatives continue to bring the walls to life in a range of contexts, from the interiors of yachts and car-parking buildings to airport lounges. Indoors, specialised lighting is required to enable the plants to grow.
The system, which is patented to Blanc, is simple. Metal brackets and a waterproof membrane allow it to be attached to any building, old or new, without damaging the integrity of the structure. The plants or cuttings are placed in pockets – mimicking crevices – cut in felt made from 100% recycled synthetic materials.
The felt mimics the layer of moss and humus that is a building block of a stone ecology and creates an appropriate surface for the plants to grow on. It also disperses and regulates nutrient-rich water. Excess water is collected and redistributed to other garden areas. The double-layered felt is only 6mm-thick, ensuring it is lightweight even when holding water, allowing Blanc’s gardens to reach as high as a project requires.
This non-biodegradable material absorbs pollution, which is absorbed by the plants as they grow. As with all hydroponic systems, the plants need a carefully calculated liquid feed added regularly to the irrigation. The water is supplied from tanks, which can be filled with rainwater or waste water from the building. The walls also act as a default insulation system that heats in winter and cools in summer.
The benefits of turning the external layer of vertical concrete into a fresh-air factory are obvious, but the walls can also become holding banks for a diverse range of endangered species. These complex plantings respond well to the various conditions found on a flat wall; for example, high areas require plants tolerant of exposure to greater extremes, and street-level plantings possibly need to be tolerant of low light. It also means the walls find their own natural balance, unlike a monoculture, which is more vulnerable to disease and more inclined to nutrient imbalance.
Green walls installed on tall buildings are maintained using the same built-in mechanical systems used for washing the high windows. A well-designed planting plan should need maintenance only twice a year.
Although the cityscape is where vertical gardens have the most impact, they are not irrelevant in the home garden, where some of the more affordable systems can be used. For example, Gabian-style boxes, which effectively act as soil-filled building blocks, are an enjoyable way to apply some aspects of Blanc’s vision to the suburban garden. These boxes are suitable for creating a feature wall that is a living work of art. Equally, they are an effective way to increase food production on a north-facing vertical plane.
Also available are woollen pockets, which can be used to create a similar effect on an existing wall. Remember, though, that these soil-based systems are effectively the same as pot plants and need to be maintained in a similar way.
Blanc’s work continues in countries around the globe, with commissions on every continent. He combines this with his fieldwork, which he puts before the art. Appropriately, he even has a plant, Begonia blancii, named after him. He discovered it in the Bolivian wilderness on one of his expeditions.
When we take inspiration from his creations, we can do so with an understanding of the great plantsmanship, artistry and vision he has shared with the world, even if ours is on a humbler scale.