Description: This grey, crustose epiphyte is a ‘dry-side’ species and is common on a variety of acid-barked trees. It may also occur on wooden posts and gates. However, it is especially attracted to mature oak bark. It is usual for the grey thallus to be covered in tiny black dots (pycnidia) which are not the same as discs. Discs though, can occur in suitable habitats and are flesh-coloured with a thick veil of pruina like icing sugar across the top. It is common on the sheltered faces of hedgerow and former parkland trees throughout Ireland.

Key Identification Features:

• The black pycnidia scattered over the thallus help to suggest this species, which does not always produce discs
• Look for it on the unwetted surfaces of large, well-illuminated, oak trees where it often grows mixed in with green or brown, powdery crustose species.

Original text submitted by Simon Davey

Distribution Map from NBN: Cliostomum griffithii at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Cliostomum griffithii at iNaturalist World Species Observations database.