Against the Odds: Lichen

Here's one of my school geography lessons in action: lichens colonising our bedroom windowsill. In this context they're known as a pioneer species and as the windowsill has had no vegetation previously, this is known as a primary succession.

At school we studied this kind of colonisation on rocks and lava flows. I never expected to find it so close to home, nor happening on plastic! I wonder what kind of food the lichen is gleaning from its unusual home?

In the long term this probably isn't doing the windowsill much good, but I haven't the heart to clear it off as it's far too interesting. Many lichens are an indicator of clean air - I must look these up to see if they fall into that category.

You may also like to look at OPAL's Air Survey and the role lichens play as an indicator of clean air. Looking briefly at their lichen guide, I see the yellow lichen is a leafy Xanthoria, which is a nitrogen-loving type.

Against the Odds: an occasional series on Veg Plotting looking at plants in unexpected places.

Footnote: a few days after I scheduled this post, The Telegraph issued a photo gallery showing Digging for Victory during WWII. It includes a garden created in a bomb crater - now THAT shows gardening against the odds!


  1. Our plastic windowsills are getting what appears to be a grey mould in them. Not so pleasant. (Aren't plastic windows horrid full stop?)

    Lichens, though, are wonderful. The Common Orange type (the zanthoria you mention) - isn't that an indication, not of clean air, but of polluted - e.g. by chemicals used in farming? and traffic? We have a lot round here (Xanthoria parietina). It's pleasant and fascinating stuff. I think our air is pretty clean - it's just that this lichen likes coastal areas because of all the nitrogen released by gull excrement.

    Oh, I do like to be beside the seaside . . . Oh I do . . .

  2. I remember those geography lessons - I spent a field trip wandering around sand dunes to study succession. The more I read about lichens, the more I like them.

  3. It does look rather lovely. What harm would it do to the plastic? We are bickering about PVC windows. Had wood, needed varnishing. Have aluminium but this manufacturer has gone. Seem to be landed with PVC.

  4. Very learning more about lichens

  5. I adore lichen and would exactly as you do about cleaning it off. I very much like the yellow ones on the roofs at the seaside - I'm thinking Bexhill; and found some lovely white ones in a graveyard in Kent the other day. Not that I ever go to the trouble of learning their names - it's just their other worldly form that enchants.

  6. Esther - yes they are! Xanthoria likes nitrogen which suggests they're not clean air indicators. Though as you say, there are other sources of nitrogen. I suspect ours is from a combination of the local bypass and farmland.

    Matt - welcome! We studied sand dunes too - happy times :)

    Diana - if the action is the same as on rocks, then it'll be breaking down the plastic to obtain minerals from it. We had PVC by default because that's what tends to be used with new houses. It's the one thing I would have liked to change with our house when we bought it.

    Donna - lichens are very cool :)

    Colleen - our local wildlife trust has a graveyard conservation project in which the lichens there feature highly. Unfortunately they don't have a website - I so wanted to provide a link with this piece.

  7. Wow - I wonder if the lichen will actually decompose any of the plastic? Come to think of it, lichen can live off hardly anything as long as they have minimal light and moisture.

  8. Janet - isn't it!

    Jay - I don't know for sure, but I think it may. If it can break down rock to start soil formation, then why not plastic?


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