Description: Recorded only from east Donegal, C. callosa is a rare member of the Cladonia tribe. It grows best on peaty or waterlogged surfaces including exposed peat hags. Squamules dominate the thallus but attention should be drawn to their curiously fragile brittleness, range of olive-green tones and tendency to bronze, otherwise only seen in C. strepsilis which is C+ emerald green. In C. callosa all spot tests are negative.

Key Identification Features:

• Thallus: a mat of brittle squamules, olive-green or grey-bronze, white below
• Spot tests negative; on the walls of peaty soils and hags on gritty sandstones.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Cladonia callosa at iNaturalist World Species Observations database.