• Question: What makes a Mediterranean cistus plant spontaneously combust and how are its seeds flame resistant?

    Asked by botanygeek to Kate, Kieren, Nicola, Rowena, Roy on 10 Mar 2014.
    • Photo: Rowena Fletcher-Wood

      Rowena Fletcher-Wood answered on 10 Mar 2014:

      Hey, maybe this should have been in the plants section!

      I only know about cistus purpureous, which is only a related kind of rock rose. In peaty bogs you often get methane vapour which leads to shots of flames that seem to come out of nowhere and gives what looks like a low mist on the ground. I’m guessing the Mediterranean cistus also has a chemical in its leave that is very flammable. Being Mediterranean, it gets pretty hot and the chemical sets on fire.

      Flame resistant materials usually just withstand very very high temperatures, like ceramic materials. Did you know wool is supposed to be flame-resistant?

    • Photo: Kate Nicholson

      Kate Nicholson answered on 10 Mar 2014:

      I have no idea but that’s a very good question!

    • Photo: Nicola Rogers

      Nicola Rogers answered on 12 Mar 2014:

      I had to look this up as I had no idea – it seems that the plants produce an aromatic resin which coats their leaves. The aromatic compounds are quite volatile and flammable – so if the sun is shining on the plants on a hot day they can catch fire and burn the plant.

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