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The myth

Ivy causes decay in the walls of buildings on which it grows.


The “truth”

Not only does ivy not generally harm buildings, according to research commissioned by English Heritage, it may actually be good for them. It’s long been assumed that ivy damaged masonry as its supporting roots worked their way into the pointing, loosening the bricks. Latest findings suggest that this belief comes from observers misunderstanding the order of events – in other words, that the plant establishes especially well on already unsound walls, and then gets the blame when their decay becomes visible. A three-year study by Oxford University biogeomorpho­logists concluded that ivy-clad buildings enjoyed significant advantages over naked ones. The covering helped regulate the temperature of the masonry during brick-cracking extremes of both hot and cold weather, as well as absorbing some of the harmful pollutants in the air. The parallel myth – that ivy is a parasite which “strangles” healthy trees – has long been dismissed by arborists. Ivy isn’t parasitic, and its excessive presence on a tree is almost always a symptom, rather than a cause, of decline.


Sources

Ivy protects by regulating temperature; The Independent
Ivy offers protection; The Medieval News
Ivy can protect old walls; Science Daily
Ivy – Friend or Foe; Arbor Ecology  
Ivy proves growing worry; The Scotsman
Garden Bird News, Oct 2009


Disclaimer

The researchers pointed out that there may well be specific circumstances under which ivy is harmful to buildings, but that the old idea that it’s automatically a menace doesn’t stand up. If you have further inform­ation, please creep over to the letters page.