I AM always surprised by how often gardening, a pursuit ostensibly all about communing with nature, can be so driven by fear. One of the most common questions I get from concerned gardeners is how to remove the supposed scourge of climbing plants, like ivy, from walls. The thinking behind this is that climbers shatter brickwork and can cause profound structural damage to buildings. But when you actually look at the science, very few of these fears are based on any evidence. And frequently, the exact opposite is true.
In a 2020 from the Royal Horticultural Society and the University of Reading, both in the UK, a range of climbing plants were found to have a protective effect on model brick buildings constructed for the experiment. The shade cast by the plants’ leaves cooled the surface of the buildings in the summer by as much as 5.7°C, reducing the wide swings between day and night temperatures – a key driver of surface structural damage.
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Despite concerns that plants trap moisture against brickwork, leading to damp issues, the same trial found this wasn’t the case. Ivy didn’t significantly raise humidity levels – rather, it helped stabilise them, minimising fluctuations that could damage the buildings’ surfaces. The living coating also lowered summer temperatures inside the buildings by up to 7.2°C, and was even projected to reduce heating bills by as much as 20 per cent in the winter.
It is worth bearing in mind that these results were from brand new, model buildings with pristine brickwork. What about real-world, well-used buildings, whose exteriors may have already experienced centuries of environmental damage?
Well, another , this one from 2011, found that in five historic buildings across England, bare walls experienced average maximum temperatures 36 per cent higher and minimum temperatures 15 per cent lower compared with those coated in a protective shroud of leaves.
The researchers concluded that the living insulation provided by ivy would “reduce the likelihood of frost and salt deterioration to the building materials, thus contributing to their conservation”. They also , in another study, that the leaves’ ability to trap pollution could reduce the damage this can cause to historical walls, and even reduce human exposure to the noxious compounds in vehicle pollutants.
Imagine if there was a new material that could cool cities and cut energy bills, all while looking beautiful and costing a fraction of the price of alternatives. Did I mention it was also self-cleaning and carbon negative? The truth is that we have had this miracle material all along, but rather than appreciating it, we have spent huge amounts of time worrying about how to rip it out.
James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, in London, he shares his tiny
flat with more than 500 houseplants. You can follow him on X and Instagram @botanygeek
For other projects visit newscientist.com/maker.
