Witches' butterExidia glandulosa

Witches' butter (Exidia glandulosa), also called black witches' butter, or witch's butter in the British Mycological Society's list, is a black jelly fungus that sits in separate 'buttons' or little spinning tops on dead branches, most often of oak. Its Latin name glandulosa means 'covered in glands': the top is dotted with tiny black pimples. In dry weather it shrinks to a thin black crust, then swells and comes back to life after rain. The name 'witches' butter' is shared with other jelly fungi, including the yellow brain, which can be confusing.

How do you identify witches' butter? Fresh fruit bodies are jelly-like and rubbery, button-shaped or pressed flat at first and attached at a narrow point, then top-shaped like an upside-down cone, or almost cup-shaped, usually 1 to 5 cm across. They grow singly or in groups and sometimes partly fuse. They're dark grey to brownish grey, later brownish black, almost black. The upper surface is uneven and dotted with small black pegs, while the underside is felty with dense blackish hairs. It's fairly firm for a jelly fungus. The spore print is white. In dry weather it becomes a thin black crust on the wood that's easy to miss.

Where does it grow? On dead branches of broadleaved trees, either still attached or freshly fallen, most often oak, less often beech, hazel, alder, ash and others. It's one of the first fungi to move into dying branches and causes a white rot. As a dry crust it's present all year, and it's most noticeable as fresh black jelly from late autumn to spring, after rain and in mild spells. It's common wherever there are oaks.

Is witches' butter edible? No, it isn't eaten: it's rubbery, tasteless and too small to bother with. We found no reports of poisoning, but there's no good evidence that it's safe either.

What can you mistake it for? The closest lookalike is the black bulgar, also black, rubbery and top-shaped, and also on felled oak. But its top is completely smooth, its sides are felty dark brown, its flesh is ochre-brown and its spore print is black, so it stains your fingers. Jelly ear is ear-shaped, reddish brown with a purplish tinge, with thin, translucent lobes, and grows mainly on elder. Yellow brain, which some people also call witches' butter, is bright yellow to orange and brain-like. Outside our catalogue, the usual mix-up is warlock's butter (Exidia pithya, formerly E. nigricans), which spreads in merging, brain-like black sheets up to 30 cm and has a smooth underside. A near-identical species, Exidia truncata, with a rough rather than hairy underside, was split off in 2026 and can really only be told apart under the microscope.