Ireland's Biodiversity Awareness Campaign

Witches’ Butter - Exidia glandulosa

Witches’ Butter – Exidia glandulosa





The Witches’ Butter is a fungus that is widespread in Ireland and found throughout the year – not just at Halloween!


Fungi do not get their food from photosynthesis the way in which higher plants and algae do. Instead, they obtain their nutrition from dead or living matter through absorption of nutrients into their cells.  Simple molecules are absorbed directly but more complex ones are broken down by enzymes released by the fungus to enable absorption.



 The Witches’ Butter ‘fruiting body’ (which is the visible, spore-producing part of the fungus) is a blackish, gelatinous blob that is covered in pimples. It commonly appears in brain-like clusters on dead/decaying branches of broad-leaved trees such as oaks and beeches.  The individual fungus bodies often fuse together to create large gooey blobs that spread across the trees’ branches and trunks. When dry, the Witches’ Butter becomes thin and crusty, however with more water, it can plump up again to look like a fresh specimen.


There has been much speculation over the origin of the unusual name. Some Eastern European legends tell of the fungus appearing over the entrances of houses whose owners have been put under a witches spell. The only way to get rid of this curse is to prick the Witches’ Butter allowing the evil juices of the fungus to leak out. However, other stories claim that stabbing the fungus would cause the witch to appear. Despite its name, most scientists believe that the Witches’ Butter is inedible. Either way, it’s probably best to steer clear of the Witches Butter, especially around Halloween…!



For more information on the Witches’ Butter and Fungi in general, you can contact the following organisation:


The National Botanic Gardens of Ireland,







©2007 Department of the Environment, Heritage and Local Government