Kretzschmaria …
Kretzschmaria deusta, commonly known as Brittle Cinder, is a formidable plant pathogen, one capable of inflicting serious structural damage on trees by instigating deep-seated decay in the root system and lower stem. Its fruitbodies emerge as wavy-edged cushions or crusts fused tightly to the timber they inhabit. When young, they appear grey with pale, almost luminous margins, as in the attached image. With age, however, they darken to a coal-black crust that breaks at the slightest touch, becoming so brittle and so charred in appearance that they are easily overlooked, their fungal origins nearly indistinguishable from burnt wood.
Though it may not be counted among the more glamorous woodland species, K. deusta reveals a quiet fascination when examined closely. For scale, the specimen shown, photographed in Surrey woodland, measured roughly 35 mm across, a small but telling sign of the intricate dramas unfolding within the forest’s heart.
References:
Sterry, P. and Hughes. B. (2009). Collins Complete Guide to British Mushrooms and Toadstools. London: HarperCollins, p. 328, fig. p. 329.
https://www.first-nature.com/fungi/kretzschmaria-deusta.php [Accessed, 9th December 2025].