Good afternoon, friends, and Happy Labor Day.
This week we’re going to look at one of the more colorful mushrooms in the woods, the Bicolor Bolete (Baorangia bicolor). I’ve seen these two-toned boletes a few times this summer, but trying to confidently identify them is nearly impossible. I got knee deep in the weeds trying to find an ID, but fortunately for us Michael Kuo swan dived into these cryptic species about a decade ago. These red and yellow boletes are some of the most numerous mushrooms in the woods right now, so let’s leave our desire for a definite ID behind and see what else we can learn from them.
Fun Facts
These mushrooms are red, yellow, and blue (when handled) . The reason why these mushrooms produce the colors they do isn’t fully understood. Perhaps it’s to signal edibility or inedibility, to attract insects, or the color is just a biproduct of the chemicals in the mushroom (I doubt it, that wouldn’t be as fun). One study out of Europe found that mushrooms further from the equator will produce darker colors, in the same way animals in those regions do, and the theory is that they do this to attract sunlight and warm themselves (Reference 2).
Another study, in fact the only scientific study with B. bicolor on PubMed, looked at the amount of radioactive compounds in bolete mushrooms from the Yunnan Province of China. They wanted to see if cooking the mushrooms had an impact on the concentration of radioactive compounds in the mushrooms. It turned out that cooking the mushrooms did help remove some of the radioactivity - yet another reason to always cook your mushrooms :). Stir-frying B. bicolor halved the concentration of Caesium 137 and resulted in an almost nine-fold reduction in Potassium 40.
The compounds Caesium 137 (137Cs) and Potassium 40 (40K) are radioactive isotopes that are released into the atmosphere after nuclear explosions, or nuclear fallouts like those at Chernobyl and Fukushima. Both of these compounds have a long half-life (the amount of time it takes for a quantity of said compound to reduce to half of the original concentration). Radioactive Potassium (40K) has a half-life of 1.25 billion years, so yes it can persist in environments for a while.
Fascinatingly, when these compounds are deposited in the soil after a nuclear incident, fungi are quick to absorb them and send them to their fruiting bodies (the mushroom). Why? Beats me, but from my understanding fungi will also do this with heavy metals. Maybe they’re able to get energy from the isotopes or metals? Or it’s a way of disposing of them since the mushrooms will not persist as part of the organism? Lots of questions, not many answers.
Ecology
Bicolors are mycorrhizal with oak trees and these mushrooms popped up between a couple of mature oaks. The mushrooms grow in North America east of the Rockies during the summer and fall, but predominantly in July and August. There are a lot of similar species, which we’ll address in a second, but there is also a lot of variability in appearance within this species. Boletes of Eastern North America considers this species a “complex”, with several genetically unique individuals masquerading under the B. bicolor name.
It’s hard to get a good grasp on these mushrooms when they only grow two months of the year and the individual specimens only last for a week or so.
There are a lot of similar species, too many to list. The biggest confusion seems to be between the Baorangia bicolor and Boletus sensibilis, especially because “online knowledge” - perhaps an oxymoron, but that would do a disservice to all the work Michael Kuo has put into the topic - suggests the former is edible while the latter is toxic. I don’t believe this notion and my understanding is that these bicolors and look-a-likes are edible. My basis for this understanding comes from the handful of eastern European women I’ve run into that lick the bottom of boletes and only toss them if they’re bitter. I’m not endorsing that technique, but I definitely endorse the people that practice it.
Kuo notes that the appearance and blue-staining of B. bicolor can be quite variable, but he also says that these are the most common boletes he sees in his woods of Ohio. Some people say the smell of “curry” can be a helpful identifying characteristic, but he rejects that notion saying all these species can or cannot smell like curry.
How I’ve started to go about these red, yellow, and blue-staining boletes is to call them B. bicolor or “Bicolors” in the field, and then hope I find another mushroom shortly thereafter so I don’t think too hard about it. If that’s not enough for you, consult this sheet and get knee deep in the weeds.
Events + Housekeeping
Beginning next week, expect a lot of Toadstool Tuesdays this fall. I’m enrolled in a soil science course that is going to meet on Monday evenings.
Here are some of the mushroom events we’ve got going on this month:
9/15: Walk with the Stamford Land Conservation Trust. Meet at the end of Gun Club Road in Stamford, CT at 10AM.
9/20-9/22: Friends of Fungi Fall Retreat at Menla in Phoenicia, NY. Find out more here.
I’m going back up to the Adirondacks next weekend to hike some of the Northville Placid Trail so we’ll get more ADK mushrooms next week.
New moon tonight,
Aubrey
References:
Kuo, M. (2015, January). Boletus bicolor. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_bicolor.html
Krah, FS., Büntgen, U., Schaefer, H. et al. European mushroom assemblages are darker in cold climates. Nat Commun 10, 2890 (2019). https://doi.org/10.1038/s41467-019-10767-z
Falandysz J, Zhang J, Saniewski M. 137Cs, 40K, and K in raw and stir-fried mushrooms from the Boletaceae family from the Midu region in Yunnan, Southwest China. Environ Sci Pollut Res Int. 2020 Sep;27(26):32509-32517. doi: 10.1007/s11356-020-09393-w. Epub 2020 Jun 7. PMID: 32506414; PMCID: PMC7417414.
Kuo, M. (2015, January). Boletus sensibilis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_sensibilis.html