Flat Crep (Crepidotus applanatus)

Good evening, friends,

This Saturday I was back down in New York for a wedding (congratulations Charlie and Claire) and got to catch up with the New York Mycological Society at my old stomping grounds, Manitou Point Preserve.

Unfortunately, I only got to hang with the group for an hour — I felt a bit like a Mushroom Monday mercenary as I found the mushroom I was going to write about, the flat crep (Crepidotus applanatus), and then left to get changed for the wedding. It was dry, though, so I wasn’t missing out on too much fun in the fleshy fungi world. The flat crep is a mushroom I see every year (usually multiple times a year), but they never got the MM spotlight until today.

Crepidotus, there for us when other mushrooms aren’t.

Fun Facts

The mushroom is fairly bland in terms of appearance, but the shape is technically pleurotoid, which means “like a Pleurotus”. Pleurotus are oyster mushrooms. The main difference between Crepidotus and oyster mushrooms is that the former have brown spores and the latter have white spores. Crepidotus are attached directly to the wood, as well, they don’t have a neck-like stipe lifting them off the substrate.

Back in 2022, I found the fruiting of Crepidotus seen below while hiking in Fahnestock State Park in New York:

Fairly normal fruiting of Creps in the hollowed out heartwood of a tree. What’s that white, ruffled growth at the top, though?

I saw what I thought to be litter — perhaps a crumpled up white, plastic Hawaiian lei. Turns out it was a Crepidotus fruiting body parasitized by a different fungus, Hypomyces tremellicola. That was the only time I’ve ever seen this Hypomyces (which parasitizes Crepidotus mushrooms) despite my frequent encounters with the latter — certainly an unusual occurrence.

Etymology

The name Crepidotus is derived from the Latin crepid- which means “base” or “shoe”, and -otus which means “ear”. The species epithet, applanatus, comes directly from the Latin word for “flattened”. What’s in a (latin) name? Well in this one it tells you the mushroom is flat, ear-shaped, and attaches directly to the wood.

You can see the brown spores of the mushroom coating the wood directly underneath it. I wonder if the insect is eating the spores or just hanging out. Centipedes are strictly carnivores, though, so it may just be a comfortable nook.

Ecology

The fungus is saprobic and digests the dead wood of deciduous trees. Although, one study found the fungus can also exist in the guts of earthworms and get transported by the worms throughout the soil (Reference 3).

While the fruiting bodies may be flimsy, the mycelium inside the wood has to be fairly robust as it persists on old, dry logs and the mushrooms can grow during dry conditions. C. applanatus seems to have a cosmopolitan distribution, growing on all six major continents (sorry, Antarctica), and the mushrooms pop up late spring through fall.

Creps frequently grow overlapping each other so it’s common to see one cover the other in spores.

There are a handful of different Crepidotus species we’ll get in the northeast. C. applanatus tends to be the largest and is hairless on the cap besides some fur toward the point of attachment. The orange crep (C. crocophyllus) is another common species, but those mushrooms are orange, hairier, and smaller. The peeling crep (C. mollis) is a larger species with a cuticle (cap surface) that peels away from the rest of the cap. Tom Volk and Jon Palmer made a key to the genus for all of North America.

C. applanatus have crowded, robust gills.

Upcoming

I will be in Telluride, CO all week volunteering at the Telluride Mushroom Festival. Next week is looking like a Toadstool Tuesday written on the flight home, because I’m hoping to get to Arches National Park for a couple days after the festival.

8/20 at 10AM: Mushroom Walk with the 300 Committee in at the Ashumet Holly Wildlife Sanctuary in Falmouth, MA

8/28 at 10AM: Mushroom Walk with the Cape Cod Mycological Society at Santuit Pond in Mashpee, MA.

8/29-8/31: COMA Clark Rogerson Foray

9/5-9/7: Friends of Fungi: Foraging Weekend Retreat with Catskill Fungi at Menla Retreat and Spa in Phoenicia, NY

I’ve also updated my events page which stretches further into the fall.

Worked right up to the Mushroom Monday/Toadstool Tuesday witching hour. I have an ungodly early flight tomorrow (boarding begins at 4:50AM), so let’s try and get a few hours of sleep here. I turn into a bit of a drama queen when I don’t get my eight hours so wish me luck tomorrow,

Aubrey

References:

1. Kuo, M. (2023, August). Crepidotus applanatus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/crepidotus_applanatus.html

2. https://botit.botany.wisc.edu/toms_fungi/jul2007.html

3. Aira M, Gómez-Roel A, Domínguez J. Earthworms Significantly Alter the Composition, Diversity, Abundance and Pathogen Load of Fungal Communities in Sewage Sludge from Different Urban Wastewater Treatment Plants. Pathogens. 2025 Apr 24;14(5):409. doi: 10.3390/pathogens14050409. PMID: 40430730; PMCID: PMC12114242.

4. https://www.fungusfactfriday.com/179-crepidotus/

5. https://www.first-nature.com/fungi/crepidotus-applanatus.php

6. https://mushroomobserver.org/names/587/map?q=25qnn

7. https://www.inaturalist.org/taxa/350514-Crepidotus-applanatus

8. https://www.inaturalist.org/taxa/350514-Crepidotus-applanatus