One way to get kids interested in lichen is to ask them to find the secret writing on woodland trees. The ‘writing’ is made by a lichen, Graphis scripta, which forms long narrow wiggledy black fruiting bodies (apothecia) on its pale smooth crust.

Not surprisingly, this lichen’s common names include script lichen, secret writing lichen, pencil-mark lichen, or hieroglyphics lichen. It is very common on smooth-barked deciduous trees, their twigs and branches, and can be found around the world – does the writing change its language depending on location, I wonder?

Lichens are very sensitive to air quality and, as they are able to accumulate and retain heavy metals, they are often used as a tool to monitor heavy metal pollutants in the atmosphere. Graphis scripta has been utilised in this way by scientists studying air pollution in the Indian city of Bangalore.