Witches butter

October 30, 2011, 11:46 am
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Witches butter on branch, Rindge, New Hampshire. Source: J.Carmichael

Witches butter (scientific name: Tremella mesenterica) is a cosmopolitan jelly fungus broadly distributed in temperate regions of the world. Although often present on rotting hardwood, it actually parasitizes a true saphrophyte. Its vivid yellow-orange glistening appearance provides a dramatic highlight in predominantly brown hued winter forest floors.

For centuries, witches butter and other forest floor fungi have been associated in legendry with witchcraft, due to their haunting and slimy appearance. The very images conjure up relationships with dark forests and Halloween festivals. An alternative common name for this taxon is Yellow brain fungus.

Distribution and habitat

This species is extremely widespread occurring at elevations up to 1420 meters in Northern Europe, Taiwan, Japan, China, North America and Australia. In North America, T. mesenterica occurs primarily in low elevation hardwood forests of southern Canada and the continental United States. In Europe, the species is found chiefly in northern countries such as Finland, Sweden, Switzerland, Germany, England and Scotland. Examples of specific associations of occurrence include the Sarmatic mixed forests of northern Europe and North coast California oak woodlands. Within Australia, T. mesenterica is found mainly in near coastal areas of New South Wales, Victoria and South Australia, and southwest Queensland; the Australian habitat is chiefly rainforest and eucalyptus forest.

Physical description

T. mesenterica occurs in a convoluted and lobed clump approximately three to five cm high and five to ten cm in diameter, (Young) although multiple closely spaced clumps are not uncommon. The lobe margins are typically blunt. The organism exhibits a fleshy translucent yellow-orange color, and is moist after rains, but not viscid; upon drying, its appearance is duller. Although the species is devoid of a stem and is apparently attached directly to a rotting log, the systemic attachment is actually parasitic to Peniophora, a resupinate fungus genus, or certain species within the genera Stereum and Laeticorticium.

Witches Butter is without odor emanation or taste. The micromorphology of this species features typically smooth hyaline ellipsoidal spores of characteristic dimensions 10-15 x 8-10 microns; sporeprints are white. Basidia are longitudinally septate. and measure 20-30 x 16-21 microns. The hyaline hyphidia have very thin walls and are sparse. Sterigmata measure up to 100 microns in length.

T. mesenterica produces a sex pheromone tremerogen, a lipophilic peptide similar to the alpha factor of Schizosaccharomyces cerevisiae. Studies (Griffin) on T. mesenterica were the first to yield evidence that diffusion hormones control the fertilization process in Basidiomycota. In this process, it has been determined that the sexual forms of T. mesenterica manifest yeast-like cells and can be described as heterobasidiomycetic yeast. The sex hormones induce formation of chemicals (Khokhlov) that in turn stimulate formation of mating tubes in cells of the opposite type. It has also been demonstrated that the sex hormones induce a dramatic change in protein types produced, particularly in increased formation of acid phosphatase.

Similarly appearing taxa

Tremella aurantialis a very similar species, but has spores slightly smaller {Roberts} and more globose, with basidia which are stalked rather than sessile. This species commonly occurs in southern West Australia and may appear in conspicuously dense clusters, literally covering its substrate log. T. aurantia parasitizes the wood rotting fungus Stereum hirsutum. Dacrymyces palmatus exhibits macroscopic similarity to T. mesenterica, but it is more orange, and is a saprophage to conifers. It is also identified by a whitish attachment point to its substrate. Microscopically, a tuning-fork shaped basidia distinguishes this taxon from the cruciate shaped basidia of genus Tremella.

Ecology and conservation

Tremella Mesenterica is found on oaks, beech, hornbeam, alder and other mostly hardwood species in North America and Europe; in Asia and Australia this jelly fungus is also found on eucalyptus and a variety of rainforest hardwoods. In North America T. mesenterica is associated with some of the most highly productive deciduous forests, such as California Black Oak dominant stands, which exhibit high biodiversity (Hogan) and nutrient cycling. Understory associates often feature ferns; for example, in the California North Coast Ranges, Polypodium calirhiza and Pellaea andromedifolia are typical alliant species. Most frequently T. mesenterica adheres to dead limbs, to which bark is still adnate. While this species cannot be considered vulnerable, its importance is clear for nutrient recycling and soil manufacture within hardwood forests. Its abundance and role in such forests is threatened by systematic deforestation as the human population further expands. Such fungi also demonstrate the significance of avoiding overpruning and removal of snags and fallen trees in hardwood forests.


  • David H. Griffin (1996) ''Fungal Physiology'', Published by Wiley_Default, 472 pages ISBN 0471166154
  • Tony Young, A. M. Young and Kay Smith (2005) ''A Field Guide to the Fungi of Australia'', UNSW Press, 240 pages ISBN 0868407429
  • A. S. Khokhlov and E. M. Suscenko (1991)'' Microbial Autoregulators'', Published by Taylor & Francis US, 450 pages ISBN 3718649853
  • P. Roberts (1995) ''British Tremella Species I: Tremella aurantiaca & T. mesenterica''. Mycologist 9: 110-114. 
  • C. Michael Hogan (2008)  California Black Oak: Quercus kelloggii,, ed. Nicklas Stromberg


Hogan, C. (2011). Witches butter. Retrieved from


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