21/08/2026
🌿 When we talk about wildlife in our cities, we usually think of birds, plants, butterflies and other insects. But how often do we stop to notice the unassuming forms of life living alongside us?
Today, in our series, we’re taking a closer look at one of these small urban inhabitants — Common Orange Lichen (Xanthoria parietina).
🔬 Did you know that a lichen isn’t actually a single organism? It’s a remarkable partnership between a fungus and a photosynthetic partner — in Xanthoria parietina, a green alga — living together as one.
🌳 Despite what you might think, Xanthoria parietina doesn’t harm the trees it grows on. It can also happily make its home on rooftops, brick walls, rocks, concrete and other hard surfaces.
🌍 Lichens can also act as natural records of air pollution. They absorb substances from the atmosphere and rainfall and can accumulate pollutants, allowing scientists to study the environmental conditions of an area.
🟠 And what about that beautiful orange colour? It comes from a pigment called parietin, which helps protect the lichen from intense sunlight and UV radiation. Historically, Xanthoria was also used to produce yellow and orange dyes for textiles.
🌿 This yellow-orange lichen was once used in traditional medicine to treat jaundice, kidney problems, toothache and coughs.
🧪 Today, scientists are investigating its chemistry, including the antibacterial properties of parietin and lichen extracts. These effects have been demonstrated in laboratory studies, although that certainly doesn’t make the lichen a medicine.
🚀 And finally, something rather unexpected: its remarkable ability to survive extreme conditions has made lichens interesting to astrobiologists. Xanthoria parietina has been studied after exposure to vacuum, extreme temperatures, UV radiation and Mars-like conditions.
✨ So next time you spot a little orange patch on a tree, wall or rooftop, take a closer look. There’s a surprisingly rich story hiding in it.
Does Common Orange Lichen grow on your roof? 🟠
