Buglossoporus quercinus

August 1, 2022

Good evening, friends,

This week’s mushroom is a real mouthful – Buglossoporus quercinus, commonly known as the oak polypore. I found this mushroom on Friday afternoon while on a run through the woods. There wasn’t much fungal activity but these polypores caught my eye from a distance. I thought they might be Cerioporus squamosus, but the season wasn’t right. As I crouched down for a better look, I quickly realized this was a mushroom with which I had no familiarity. Dawning nothing but skimpy running shorts and sneakers, I felt vulnerable and exposed – I was unprepared for a myco-surprise of this magnitude.

Fortunately, I was able to call an EMT (Emergency Mushroom Technician), Ciara, and she was able to meet me with a hand lens, pocket knife, camera, and paper bag for collecting. Thanks to the heroic efforts from this fungal responder, we’ll even get to peak at the spores of this elusive mushroom.

Fun Facts

B. quercinus is listed as “Vulnerable” by the International Union for Conservation of Nature (a United Nations program). As it turns out, I wasn’t the only one in the encounter feeling a little vulnerable. It also has the highest level of legal protection in the UK, established through the Wildlife and Countryside Act of 1981, and is one of only four non-lichenized fungi to receive that distinction. Interestingly, the largest known population of the fungus exists in Windsor Great Park, an area formerly preserved as a hunting forest for British royalty with oak trees ranging from 500-1000 years old. In the UK these mushrooms are found growing from these living ancient oaks but, conversely, all the North American specimens have been found growing from dead, well-decayed oak.

Though the mushroom is uncommon, this particular organism was fruiting robustly, and smaller mushrooms were popping through buried oak wood. It’s fascinating how the fungus is able synchronize mushroom production while living in different pieces of the oak since the mycelium is not connected between the separate logs.

Another interesting feature is that while it is a polypore, it develops a pseudo-stipe and doesn’t just attach to the wood horizontally. You can see how the pseudostipe helped the mushroom below grow vertically out of the buried wood and elevate itself above the forest floor to help aid spore dispersal.

Tom Bigelow, the former president of the New York Mycological Society, also had a contribution for the fun facts section. Apparently, Buglossoporus means “pores that look like an ox tongue”. While the pores are angular in shape, the name probably is derived more from the color they turn when bruised – presumably a similar color to an ox tongue.


B. quercinus is saprobic, growing from old-growth oaks or well decayed oak wood. In North America it’s found generally in the middle of the Appalachian Mountain Range, extending from the middle of Virginia up through Putnam County in New York. Across the Atlantic, it ranges from the UK across Europe into the Caucus mountains and Western Asia. It seems to have a large range, but the occurrence of fruiting bodies is rather rare. It grows during a finite period in the summer with the majority of the mushrooms in North America growing in July.

There’s a hypothesis that it’s an introduced species in North America since the first recorded sighting in this hemisphere was from Virginia in 2013. Despite the infrequency of its growth, it is still conspicuous enough that we’d expect it to be documented long before 2013. It’s also being observed more frequently each summer which also suggests it is an introduced species. Perhaps it’s a non-native and filling a niche that was previously void? The specific niche and ephemeral nature of the mushrooms make it difficult to believe it’s outcompeting or replacing a native species, but who knows. Most fungi don’t make mushrooms so perhaps it’s displacing old oak fungi that we don’t know even know exist.

As mentioned earlier, the white pores bruise brown when injured or handled. Even parts of the cap, and the cap margin, were bruising brown. The mushroom has white spores that you can see resting in the cap crevices in the second picture, and also through the lens of a microscope below. Nothing too remarkable about the spores, but fun to take the scope for a spin.

All in all a very exciting find that leaves us with more questions than answers. We finally got some rain so keep your eyes peeled for mycorrhizal mushrooms this week. It’s been a slow summer for them so far, but hopefully this precipitation gives way to a few decent flushes. The EMT and I will be trekking over to Tamaqua, PA for Mycofest this upcoming weekend so hopefully we’ll have a nice round-up of mushrooms to run through next week.

Happy August,

1) https://www.fungusfactfriday.com/229-buglossoporus-quercinus/
2) http://iucn.ekoo.se/iucn/species_view/100829/
3) https://pubmed.ncbi.nlm.nih.gov/15119356/
4) https://www.inaturalist.org/taxa/506309-Buglossoporus-quercinus
5) https://arboriculture.wordpress.com/2016/01/24/fungus-spotlight-piptoporus-quercinus-oak-polypore/
6) https://fungi.myspecies.info/all-fungi/buglossoporus-quercinus