Circles

Phaeophyscia orbicularis

With the garden sinking down into its winter rest, it's time to turn the spotlight back on the lichens that festoon some of the trees. I introduced you to the bright orange Xanthoria parietina last winter. Today, I'm focusing on the somewhat less obvious Phaeophyscia orbicularis — the variably grey species lurking beside the Xanthoria in the picture above. Like its orange neighbour, this is a foliose lichen, which means it's rather leafy in appearance. You can easily lift a corner of the lichen with a fingernail, as much of it isn't firmly attached to the substrate underneath. It can range in colour from from light to dark grey, with multiple colours often visible within the same colony. When wet, it's reported to sometimes go green, but that's not something we've seen yet.

Phaeophyscia orbicularis often forms circular colonies (plenty of examples above) which can grow up to 3 cm (about 1.25 inches) in diameter. However, it can also grow in more diffuse colonies, like the mass on the left side of the picture above. Such colonies are irregular, flatter and pressed more closely to the substrate on which they're growing. The center of the mature colonies tends to be densely covered with lumpy, dark, rounded soralia (the structures that contain little packets of fungal and algal cells that break off to form new colonies). As would be expected in a garden surrounded by well-fertilised farm fields, Phaeophyscia orbicularis tolerates nitrogen-enriched habitats. It's common and widespread across most of Great Britain (somewhat less so in Ireland), growing on bark, twigs, stone and concrete. In our garden, it's particularly common on the bigger branches of the apple trees.