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Warlock's Butter - Exidia nigricans

Good evening, friends,

This past week I made a vow that this publication is not going use mushrooms from the fall and summer during the “slower” mushroom months of winter and spring. I want to serve up MM’s a la carte for fungi you can find outside right now. It feels more authentic that way and we’ll get to be more in touch with the seasons. That may mean more ascomycetes and lichen in the winter, but that also means more learning about the lesser known.

This week’s mushroom is actually fairly common, and it boasts an all-time common name: Warlock’s Butter (Exidia nigricans). The past week of rain reinvigorated all the winter fungi and Warlock’s butter, Witch’s butter, and other jelly fungi are on almost every dead branch you inspect. Like regular butter, those little gelatinous mushrooms are edible, and we’ll also learn that you may also be consuming this fungus in a much more inconspicuous way.

Exidia nigricans

Fun Facts

Exidia nigricans is a gelatinous, jiggly mushroom and is known as a “Jelly Fungus”. Jelly fungi don’t comprise a single taxonomic clade, but they do all form gelatinous fruiting bodies from which they release their spores. Jelly fungi are some of the few fungi that can be eaten raw. They aren’t as chitinous (chitin-dense, hard) as other mushrooms and go down easy - although when eaten off the wood they’re not particularly tasty in my honest opinion. They taste like the branch they grow from and the texture is not for me.

As I was doing my research, I stumbled upon a study out of Thailand where researchers examined antibacterial properties of endophytic fungi (fungi that live inside plants and are thought to form a symbiosis with the host plant) in Ocimum basilicum var. thyrsiflora. The latin name is a mouthful but the plant’s common name is Thai Basil. The researchers found a species of Exidia living in the plant, as well as seven other genera (the plural for genus) of fungi that all displayed some degree of antibacterial activity. More importantly, if you’ve ever ordered basil fried rice from a Thai restaurant, not only have your taste buds experienced the pinnacle of global cuisine, but you may have unknowingly eaten Exidia mycelium living within the basil.

Exidia nigricans


Another study out of Germany (Reference 3) shed some light on the growth habits of Exidia. Anecdotally, I find these mushrooms fruiting gregariously from small, broken branches that have fallen to the ground. The study found that Exidia and other jelly fungi tend to inhabit branches higher in the canopy (not the highest, though, that was the ascomycetes). This is consistent with the thinking that the fungus is a symbiotic endophyte but once a branch begins to decline in health, or die completely, Exidia can turn into a saprobe (decomposer) and digest the wood. The production of the gelatinous fruiting bodies would then send spores to other branches where the endophyte can reestablish a symbiosis. The last part is just my ecological speculation, though, more research is needed.

The researchers also stated that “decayed wood desiccates faster in the canopy than at ground level” which was new to me and I feel like a bit counterintuitive. I always thought that once a branch hits the ground, then all the mycelium in the soil can now begin to digest it, but I guess that isn’t the case.

E. nigricans fruiting up and down the branch.
E. nigricans fruiting up and down the branch.

I’ve mostly been talking about the genus Exidia to this point because dividing up into species is complicated work. I wrote about the Amber Jelly Roll (Exidia crenata) back in late 2020, and it doesn’t appear that I’ve gained much more of an understanding on these jellies in the interim. I will say that there were Exidia all over the preserve this past week (and down in Prospect Park at this weekend’s NYMS walk) but I see E. nigricans much less frequently than E. crenata - maybe at a ratio of 1:10.

The rule of thumb I use is that E. crenata is a dark amber, red wine color and forms roundish globules that attach centrally to the wood, but grow large enough where they noticeably dangle off the branch. E. nigricans is darker in color (from a dark olive to black) and forms gelatinous mats that are brain-like in texture and the individual fruiting bodies are hard to distinguish. E. nigricans also forms larger, denser colonies that spread across the wood like in the picture up above. Then there’s Exidia glandulosa which seems to be a mix of the two - the black color of E. nigricans but a rounder, larger shape closer to E. crenata. If you’re still following along, God Bless.

E. nigricans and other Exidia are found in temperate areas of the northern hemisphere, but they can now also be found in cosmopolitan areas of the southern hemisphere (likely introduced accidentally by humans). The mushrooms can grow year round but are most prominent in the northeast in the winter months. Without leaves on the trees nor herbaceous plants on the ground, the jelly fungi are a lot more noticeable. The jellies can dry out during dry periods only to rehydrate next time it rains, too.

Compare E. crenata (left) growing on a branch I found on the ground to E. nigricans (right) which was growing on a dead birch tree.
Compare E. crenata (left) growing on a branch I found on the ground to E. nigricans (right) which was growing on a dead birch tree.

Last week I forgot to alert everyone to the full moon - my bad - but this Thursday is Imbolc which is the traditional Gaelic festival to mark the start of spring. I believe there is also an important groundhog down in Pennsylvania that will have some say as to whether the weather in February will be more mild or hostile. We’ll see how it all plays out,




  2. Atiphasaworn P, Monggoot S, Gentekaki E, Brooks S, Pripdeevech P. Antibacterial and Antioxidant Constituents of Extracts of Endophytic Fungi Isolated from Ocimum basilicum var. thyrsiflora Leaves. Curr Microbiol. 2017 Oct;74(10):1185-1193. doi: 10.1007/s00284-017-1303-1. Epub 2017 Jul 12. PMID: 28698913.

  3. Unterseher M, Tal O. Influence of small scale conditions on the diversity of wood decay fungi in a temperate, mixed deciduous forest canopy. Mycol Res. 2006 Feb;110(Pt 2):169-78. doi: 10.1016/j.mycres.2005.08.002. Epub 2005 Nov 7. PMID: 16388941.




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