Rock Tripe
Lasallia pustulata
REACTIONS
DESCRIPTION
Lasallia pustulata is a large, leaf-like lichen that grows attached to rock at a single central point, rather like a button holding it in place. Because of this, it often looks like a floppy disc or shield sitting on the rock surface rather than being tightly crusted down.
The colour is usually grey to olive-brown, and it often appears greener after rain. The surface is uneven and covered in small bumps or blisters, which give it a slightly warty look. These bumps are one of the easiest ways to recognise it.
If you gently lift the edge (without damaging it), you’ll notice the underside is smooth and lacks the root-like structures that many leafy lichens have. The central attachment point is usually obvious.
Once you’ve seen it, it becomes quite distinctive and hard to confuse with anything else.
HABITAT
This species grows directly on rock, particularly on siliceous substrates such as acid igneous and metamorphic rocks. In North Wales it is most often found in upland and mountainous areas, where it favours exposed but stable rock faces, boulders, and outcrops. It tends to occur in well-lit situations with good air quality, often in places that experience regular moisture from rainfall, mist, or cloud cover, but it can also tolerate periods of drying due to its robust structure.
STATUS IN NORTH WALES
Locally common in upland areas
Lasallia pustulata is a characteristic species of rocky upland habitats in North Wales, particularly within areas such as Eryri. While largely absent from lowland landscapes, it can be locally abundant where suitable rock and clean air conditions coincide.
