Monday, May 24, 2010

Oxford Study Finds that Ivy Can Protect Walls

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This article has been linked from The University of Oxford.  For original link, click here.

"The received wisdom that ivy destroys buildings has been overturned by a new study by Oxford University.

In a three-year project, Oxford researchers analysed the effects of ivy growing on buildings in five different parts of England and discovered that the plant plays a protective role. They found that an ivy canopy was like a thermal shield, combating the extremes of temperature which often cause walls to crack.

English Heritage commissioned Professor Heather Viles of Oxford University's School of Geography and the Environment to analyse the effect of common ivy (Hedera helix) to guide them in their important role as the steward of hundreds of historical sites. Professor Viles’s research team monitored the effect of ivy on walls situated in different parts of the country with varying climates and challenges.They found that ivy acted as a thermal blanket, warming up walls by an average of 15 per cent in cold weather and cooling the surface temperature of the wall in hot weather by an average of 36 per cent. The ivy was also found to absorb some of the harmful pollutants in the atmosphere. Walls where ivy was growing were less prone to the damaging effects of freezing temperatures, temperature fluctuations, pollution and salts than exposed walls without ivy.

Professor Viles said: ‘Ivy has been accused of destroying everything in its path and threatening some of our best loved heritage sites. Yet these findings suggest that there are many benefits to having ivy growing on the wall. It not only provides colourful foliage but also provides walls with weather-proofing and protection from the effects of pollution.’

Garden walls at some of Oxford University’s old colleges (Trinity, Pembroke and Worcester Colleges) as well as the Old City Wall were test sites in Oxfordshire. Elsewhere, the research team examined whether ivy at the Dover Drop Redoubt site, one of a series of forts at Dover Western Heights, was friend or foe. Other walls were tested at Byland, North Yorkshire; Nailsea near Bristol; and Leicester in the Midlands.

The Oxford team used resistivity methods to monitor wall moisture levels and fixed monitors to measure the temperature and relative humidity of the microclimate beneath the ivy canopy as compared with uncovered walls. They also conducted laboratory analyses to examine the role of ivy in more detail.

The findings suggest that ivy has protective qualities for buildings that are intact; but they also showed that where walls are already damaged ivy rapidly finds its way into existing cracks and holes in walls. The researchers have built a test wall, planting ivy at the base, at Wytham Woods in Oxfordshire. The cube-shaped wall contains different flaws so researchers can measure and compare the different deterioration rates with and without ivy.

The project provides those working for English Heritage as well as gardeners up and down the land with a better idea of how to treat ivy. Many might otherwise be unclear about whether to cut down ivy climbing up the walls of their garden and home.

Alan Cathersides, Senior Landscape Manager at English Heritage, said: ‘English Heritage are always keen to avoid unnecessary work to monuments and hope this research will lead to a more balanced approach to ivy. Removal should not be automatic as so often in the past, but a carefully considered element of long term management.’

Out of this study, English Heritage hope to issue guidelines for staff and provide guidance for the public on their website by early next year. Meanwhile, Professor Viles and Dr Troy Sternberg of Oxford's School of Geography and the Environment, and Alan Cathersides, from English Heritage, will be speaking about the project and providing practical guidance at a one-day conference on ivy at the Geological Society of London on Wednesday 19 May. "


  1. mmm, interesting Thomas, i must confess that i usually cut ivy down whenever i can, i know it provides shelter for wildlife but on trees and walls i enjoy the simplicity of bare bark and stone. i would prefer a rose or wisteria to ivy any day although ivy on a pergola vertical is interesting, but perhaps i need to review my perceptions...

  2. The study makes a good case for ivy, or any vegetative cover for that matter, as a thermal buffer but I would comment that the study takes place in England where English Ivy is native. It has devastating effects on woodlands in other parts of the world. I am not sure why it is still legal to sell here in Maryland. Chinese Wisteria is not any better.

  3. I agree: English ivy, and spreading groundcovers generally, should not be sold. Native vines like Virginia Creeper, Crossvine, or Carolina Jessamine are much better alternatives. They are less aggressive and more attractive.

  4. In agreement with Anonymous! English ivy is a huge pest, here in California, and I know it was rampant on the side of my childhood house in Maryland.

  5. mmm, being English I now feel compelled to defend our native ivy, it's lovely provided one keeps it in check and is the perfect habitat for so much wildlife...

  6. Interesting information. Too bad the ivy at Wrigley Field in Chicago can't protect the Cubs from looking so pathetic. I know this isn't a sports forum but when I read this post I imagined the wall ivy at Wrigley :-)

  7. Very interesting post, so it isn't quite as bad as we all thought!

  8. Hi Thomas,
    Interesting that ivy can protect walls...I have a question about Ivy. I live in Montana where we see some pretty strong winters. Is there a type of Ivy that would grow well here? Also I intend on growing it over and down the other side of a retaining wall... can this be done? It seems most Ivy wants to grow upward, could it grow down the other side of a wall?

  9. We have the ruin of an old Tower House on our land in Ireland, the Ivy roots have grown though the lime mortar and caused large cracks to appear in the stonework, I would suggest that your findings do not give a balanced verdict on the possible damage caused by Ivy, you give the impression that the building will be protected without stating the other detremental possibilities.

  10. The place has a decent beer selection, my husband wasn't thrilled, but they have the english/scottish standards and we did come when they were serving $3 all in all a win for us. Taxi Oxford to London


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