Scrolling through my social media feed recently, I was stopped in my digital tracks by a truly jaw-dropping image. It was a leafy mountainside in Shengshan, China, where what looked like well over 100 houses were entirely wrapped in living green. After being abandoned in the 1990s the fishing village of Houtouwan, 40 miles east of Shanghai, had been swallowed by nature, with Boston ivy covering every possible surface – roads, multistorey buildings, old gardens, the whole lot. It was like a model railway scene dusted in emerald icing sugar. It started me thinking of the buildings I see dotted round me in London covered in this exact same vine, and the incredible impact this could have if climbers like this were planted across our cities.
Aside from the magical aesthetic appearance, we now know that healing times in hospitals can be shorter for patients looking out at green views than for those looking out on brick walls. Exercising in green spaces not only feels easier, but can even burn more calories per session, for a range of complex reasons we have yet to fully understand. In a densely populated urban environment where space is at a premium, greening vertical surfaces is a really neat way of adding enormous amounts of nature without taking up any extra land footprint.
But what effect does this have on the building underneath, and how practical is the idea? It was once assumed that climbing plants damaged building facades, but scientific research – including some really interesting work by the Royal Horticultural Society and the University of Reading – suggests the exact opposite. As long as the brickwork is in good condition at the time of planting, the leaves of climbing plants create a protective skin that shields the building’s surface from rain, heat and cold, all at far less maintenance cost than most horizontal green spaces.
The shading effect of foliage can cool building interiors by as much as 7C in summer, and the insulating effect of plants such as ivy can reduce heating bills by as much as 20% in winter. Plants, being living pumps, actually draw moisture away from the brickwork through both the action of their roots and the rainshadow created by their leaves, helping significantly reduce the risk of damage caused by damp. They can even mop up airborne pollution and reduce noise. And ivy – as it is in leaf all year round – is seemingly one of the most effective species across trials.
Imagine there was a revolutionary building material that could reduce our energy bills, cool overheated city centres, beautify buildings and even improve our health, all at a fraction of the cost of most traditional solutions. Now imagine that this natural material was also self-cleaning and automatically regenerating, and could boost biodiversity, too. It would probably make headline news. Yet climbing plants have been right in front of us all this time.
Follow James on Twitter @Botanygeek
