Black witch’s butter (Exidia glandulosa) is an interesting, though little-known, tree-dwelling fungus that has stimulated people’s imagination for centuries. Its surface is usually wrinkled, while its texture is soft and springy, especially after rain. During dry periods, it can harden and shrink, only to regain its volume after rainfall.
This fungus grows mainly on dead branches of deciduous trees, most often oak and beech, as well as on dead stumps. It can be found in many parts of Poland – including forests around Bolesławiec, where it appears particularly readily in damp and shaded places.
Old legends are associated with black witch’s butter. It was called “witches’ butter” or “trolls’ butter” because its gelatinous, slimy form was associated with a strange substance left behind by supernatural beings.
As we read in Wikipedia:
In England, this species had the folk name witches’ butter. It was believed to be butter scattered at night by witches who stole milk from cows. Since witches were associated with evil and ugliness, their butter was also black, ugly and repulsive. For the same reason, in Sweden the species was known as Troll’s butter.
In times when people sought magical explanations for unusual natural phenomena, such “black butter” on trees seemed to be evidence of nocturnal activity by witches or forest creatures. In addition, the fungus can suddenly appear after rain, which only strengthened the impression that “someone” must have placed it there.
Despite its intriguing history and distinctive appearance, black witch’s butter is inedible. Although it is not poisonous, its gelatinous, rubbery texture means it is unsuitable for consumption.