# Witches’ butter (Exidia glandulosa)

**Exidia glandulosa* and *Tremella mesenterica**

**Known today as.** Black or yellow jelly fungi that swell on dead branches after rain.

Kind: Fungus

## What was it used for?

None.

## What does modern science say?

Harmless; the yellow kind is eaten in China.

## Pharmacognosy and toxicology

- **glucuronoxylomannan**: a polysaccharide of *Tremella*
- **water**: 95 per cent

**Mechanism.** Jelly fungi of no toxin and no action; the related silver ear (*Tremella fuciformis*) is a Chinese dessert whose polysaccharide holds water in cosmetics. The name is the folklore of the thing that appears overnight on a gate.

**Dose.** Harmless.

**Standing.** Inedible for texture, not for toxin.

## What lore surrounds it?

In Scandinavian folklore it was the butter of witches or trolls; found on a gate or door, it meant a spell had been laid on the house, and piercing it with pins was thought to wound the witch.

## Sources

- Kvideland, R., & Sehmsdorf, H. K. (eds.) (1988). *Scandinavian Folk Belief and Legend*.
- Phillips, R. (2006). *Mushrooms*. Macmillan.

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*Witches’ butter.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/witches-butter

Historical description, not medical advice.