Phaeolus Body

In my early 20s I had a boyfriend who had studied forestry and liked to find every possible opportunity to use the phrase “brown cubical butt rot.” He used it when the dog farted, when I had dirt on my work pants, when we were lucky enough to come across big blocky pellets of moose poop, and in any other vaguely scatalogical context. I didn’t know it, but this boyish potty humor was my introduction to Phaeolus. ​

I made up another definition for “cubical butt rot.” I imagined it was what I’d get if I ended up in an office job, rotting in a chair in a cubical instead of doing the real stuff I wanted for my life, like art and farming. I’m lucky that I’ve been able to meander between mostly meaningful “office jobs,” art, farming, and nature-based work for the last 30 years. And I’m lucky that along that journey Phaeolus came back into my life in a different, feminine inflected, form. 

Fiber artists who forage and use mushrooms for dyes know Phaeolus schweinitzii as the Dyers’ Polypore. I imagine the knowledge of Phaeolus as a dye arose independently in multiple areas of the world. Certainly in the Nordic countries, but I’m guessing women who worked with wool and other fibers figured this one out across the fungi’s transglobal range — Phaeolus shows up everywhere there are conifers. They are common, plentiful, large-bodied, and produces a brilliant gold color without the need for mordants or special chemistry. How many other names are there for this reliable dye partner?

This is the same fungal forest dweller that foresters call a pathogen because it consumes the cellulose in the roots and butts of conifer trees, leaving weak, dry cubes of crumbling heartwood and eventually weakening its host tree to the point of toppling. Of course this is a problem if your economic livelihood is in board feet or stumpage. But forestry seems to be evolving, or getting back to its roots, and many folks who manage forests now understand dead trees as ecologically critical elements of the process that is a forest. Phaeolus, as both a parasitic and saprobic fungus, is a major catalyst for change: initiating the slow decline of a standing tree so that insects and birds can move in, then creating gaps for light and nurse logs to nourish the next generation of seedlings, and further decomposing the former tree into rich soil. Once the decomposing is far enough along that Phaeolus has no more food, they also cease to be in that locale. Spores from years of fruiting bodies carry on the cycle of enforcing term limits elsewhere in the forest.
​
This species of Phaeolus was named, in my culture, by Lewis David von Schweinitz, an early 19th century German-American mycologist and botanist. The genus name Phaeolus is from the Greek φαιός meaning “dark, obscure, dusky, dull, grey, or sombre.” It seems to me that Lewis David and other early mycologists were looking at mature, brown polypores that had stopped growing for the season, or even past seasons’ dry bodies that are visible for several years. Or maybe the reference to darkness is behavioral, because this fungi is a decomposer. The namers certainly weren’t considering the mushroom’s bright dye capabilities. For several weeks in mid-summer, when Phaeolus’s mycelial body is in prime health, the fruiting body emerges as a bright lemon yellow, velvety nub that begins to spread. The yellow growth edges leave behind orange and ochre bands and eventually a brown center, as they indeterminately expand outward and envelop everything they encounter. Pine needles, twigs, cones, herbs, other limbs of the same mushroom, Phaeolus includes it all into their fruiting body. 

Phaeolus Schweinitzii

This root word φαιός, dark and dull, seems to be a minor variation of φάος, light. To my ears, Phaeolus sounds like fire, like Phaethon, the radiant son of Helios. My two years of college Greek leave me wishing I could make sense of this linguistic relationship. I’m going to run with it, because this is the nature of Phaeolus who, in addition to ushering in death towards new life, and dyeing fibers gold, contains another whole astonishing world of light that we can glimpse but not fully grasp. 
​
They biofluoresce. And their dye biofluoresces.

Phaeolus schweinitzii’s pores under ultraviolet light

Like the generations of fiber workers who figured out Phaeolus’s color yielding properties, the current international community of mushroom dyers,
mycologists, and fungi fanatics have pointed UV spectrum “blacklights” at Phaeolus, and have been delighted with a bright yellow-green fluorescent
glow in response. 

This discovery launches us into new territory, on an altogether different plane from the potty humor we started with, to the edge of, and beyond, what humans can perceive. Phaeolus invites us to consider the experiences of organisms that interact with the electromagnetic spectrum differently than humans do. Human scientists are just beginning to research how other beings might use biofluorescence to communicate. Different from reflected ultraviolet light, which humans have no access to but many other animals can see, or the bioluminescence of deep sea and some terrestrial organisms, biofluorescence – or Ultraviolet-Induced Visible Fluorescence (UVIVF) – is an atomic state change trick. It occurs when an organism (or naturally derived dye) absorbs short wavelength light, not visible to the human eye, which excites electrons within its molecules. As the electrons revert to their normal state, they release absorbed energy in the form of longer wavelength light that humans can see, causing the organism to glow. 

It’s hard to imagine how this might work in nature without the help of a blacklight. The sun emits lightwaves in the UV spectrum, but for us, most daytime fluorescence is obscured by all the reflected light we see. Sometimes something gives us a hint of glow on the edge of our normal reflected spectrum, like antifreeze, chemical fluorescent dyes, or the “brighteners” added to laundry detergents. Natural dyers may be familiar with the mermaid glow of indoxyl, part of the indigo extraction process, or a common buckthorn dye bath, which also biofluoresces. Is there a technology that other organisms have that enhances this effect? Or perhaps there is a non-visual element to this energetic reaction?

When I come across Phaeolus in the forest, I immediately become aware of the critters flying around and burrowing into their body. I wonder if these companions are responding to what we’re calling biofluorescence or another phenomenon that I don’t have the senses to experience. Phaeolus consumes tree bodies, and at the same time seems to call in other life to feast on its own body. A mature Phaeolus is likely to be crawling with all manner of larvae, maggots, grubs, flies, millipedes, slugs, worms, and beetles, the overlooked, oft-despised creatures at the foundation of our web of life. Without fully understanding what is happening, I sense, and am awed by, an apparent engine of light and creation here in the decomposition zone, where death and life become nearly indistinguishable from each other. 
​
Imagine donning the Phealous Body and dancing in this liminal space of glowing transformation and renewal...

Phaeolus Body under natural light, installed in the Astoria Visual Arts gallery for Iris Sullivan Daire's Adoration of Light Group show in September 2026.

Phaeolus Body under ultraviolet light, installed in the Astoria Visual Arts gallery for Iris Sullivan Daire's Adoration of Light Group show in September 2026.

CREDITS
Gratitude to Iris Sullivan Daire for the opportunity to show this work in Adoration of Light at Astoria Visual Arts in September 2026.
The yarn is American grown wool / mohair, spun by Green Mountain Spinnery in Putney, VT.
The knitted garment was adapted from union suit pattern by Megan Grewal.