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!