The benefits of green walls make them worth investigation by all green-space professionals, says Miranda Kimberley.
Living or green walls have been a buzzword for some time now and they are no longer a completely new way of planting. However, there are many of us in green-space management, including head gardeners like me, who have never installed one. So this article is aimed at the novice who has been asked to start researching what is out there and perhaps to include one in their garden or landscape.
I recently attended a talk in London by Patrick Blanc, perhaps the most famous exponent of green walls. I had no idea that he is actually a tropical botanist, still working at a university, whose interest in growing plants above an aquarium and purifying the water started this foray into living walls. He has been creating these green walls now for more than 30 years and some of them are higher than 40m tall, designed in a highly artistic style with ribbons of colour and texture.
Blanc started experimenting with green walls in around 1995, with his first commercial green wall — for the Pershing Hall Hotel, Paris — installed in 2001. Now there are more than 200 providers of living wall systems around the world, with at least 30 different systems, most of them patented, as is Blanc’s original hydroponic system.
There are several different ways to install a green wall. First, a support system is built against the wall, to which the living wall can be attached. The supporting materials should be water-resistant and long-lasting — all living walls incorporate an irrigation system on which the plants rely. Many companies use a waterproof membrane or insulation layer between the supporting wall and the living wall.
The actual living wall itself can be made of many different materials. It depends whether they will be
soil-based or hydroponic. Soil-based systems generally use fabric pockets or rigid plastic panels that either have individual cells or troughs. Using individual cells means plants that are not thriving can be lifted out and replaced easily. Using soil can obviously make the structure very heavy, so lighter growing media are often incorporated.
The hydroponic systems may use horticultural felt or modular panels of rock wool or another light medium. They often incorporate water recycling and careful addition of nutrients to the water. These systems obviously absolutely rely on the water and nutrients, so the irrigation needs to be regularly checked and maintained. Failure would lead to quick plant death.
The really clever systems incorporate fish so that the nutrients added to the water by them benefit the plants above and the plants oxygenate the water for the fish below. This is known as aquaponics.