Identification notes

It is perhaps inadvisable to look at bryophytes whilst driving, but this liverwort can be recognised easily from a distance when it forms characteristic dark purple circular patches on the bark of trees. It’s usually well pigmented but young growth may be green.

Once their characteristic morphology is known, Frullania species are easy to recognise and F. dilatata is very common in most areas. It is remarkably desiccation tolerant, hence its penchant for growing high up on the bark of trees (often with Metzgeria furcata). When dry, its shoots are characteristically dull-looking in contrast to F. tamarisci, which is shiny. The lobules on the underside of the shoot are often a similar size to its underleaves and proportionately much larger than all its near relatives. It tends to grow very closely appressed to its substrate, unlike F. tamarisci, whose shoots often grow away from it. F. dilatata is more restricted to living bark than its relatives, but does occasionally grow on basic stone.

Distribution in Great Britain and Ireland

F. dilatata is widespread in lowland areas and being very tolerant of dry conditions is often the only Frullania to be seen in the driest parts of the country. In more oceanic areas of the north and west F. tamarisci is increasingly frequent and in areas with the highest rainfall can become the commoner species. Like many epiphytes, F. dilatata is sensitive to airborne pollution and has recolonised many formerly industrial areas thanks to better air quality in recent decades.