Snorkeling for "The Rogue" Mushroom

I guess it’s not so strange. When the weather is hot and a little moisture is a pleasure, we head for the swimming hole. Apparently Psathyrella aquatica has similar habits.

This small, drab mushroom would hardly be distinguishable from most other Psathyrellae species if it weren’t for its habit of fruiting underwater. This is most unusual behavior for a gilled fungus.

Darlene Southworth who is a retired Southern Oregon University Biology professor confirmed the uniqueness of the species that Prof. Coffan found. In fact the species appears to be the only gilled mushroom species known to fruit under water. All specimens were permanently submerged in cold, spring-fed waters, not merely covered by rising water, and they continued to grow in the same area for 3 months.

Dubbed Psathyrella aquatica, the “Rogue Mushroom” was introduced to the broader scientific community in a 14-page paper submitted Nov. 9, 2007 to the science journal Mycologia. The paper was written by Jonathan Frank, a laboratory technician at SOU, in collaboration with Coffan and Southworth. It was named in 2010, but its range is still something of a mystery.

So if you are vacationing and snorkeling in the upper Rogue River of Oregon, or for that matter any mountain stream in Northern California or Southern Oregon, keep an eye out for this little brown mushroom (LBM) that grows near submerged wood, and sometimes on river gravel. It apparently has only been recorded between June and late September from two locations on the Rogue. This mushroom is typically about 10 centimeters tall. It has a small bell-shaped cap about 2 centimeters wide, a thin stipe and gills. Small bubbles adhere to the cap and stem. Researchers have yet to definitively identify the gas producing those bubbles.

All this begs the questions: Are there other species that fruit under water? How are spores dispersed? What is the evolutionary history?

Limited information is available even as of 2025:

• Psathyrella aquatica on iNaturalist - 15 observations as of 2025

• Psathyrella aquatica on Mushroom Observer - 2 observations as of 2025

The section below describes the mushroom and known habitats (as of 2014), and provides instructions on what to do if you happen to actually find it. Essentially get coordinates and call Southern Oregon University to report the discovery…PLEASE DO NOT PICK IT because Psathyrella aquatica degrades rapidly).

The following guide has been published in hopes of establishing a range for the species.

Search Guide for the Rogue Mushroom

Psathyrella aquatica

Based on what was known as of 2018:

Habitat and Growth Conditions

• Fruiting from mid-June to late September

• Found on N Fork of the Rogue River.

• Found in flowing water (not in backwater or stagnant area).

• Constant baseflow (from springs rather than snowpack).

• Constant, fairly cold temperature.

• Submerged woody debris nearby (though sometimes found in bare alluvium).

• Alder usually present nearby.

• Observed on alluvium, on twigs, and among algae.

• Depth from near surface to 50 cm (20 in) below water surface.

Morphology

Cap: 1-2 cm (1/2 - 3/4 in) wide, buff-white to dark brown.

Stipe: 7-10 cm (3-4 in) tall, thin and spindly, breaks easily.

Hunting Suggestions

• The underwater photos are close-ups. In reality, these “little brown mushrooms” are small and hard to find, especially with rippling water.

• Direct sunshine helps.

• If you find one, you will likely find another.

• Slow down, look near debris at edges of a main channel, but still in flowing water near the banks or quieter shallow flow areas where silt can settle.

What to Do Upon Observation:

• Do not collect specimens. These mushrooms degrade rapidly when picked.

• Note the location (GPS, USGS map, trail mile, whatever).

• Photograph the specimen and the habitat. See Photography for ID Purposes for tips.

Contact Southern Oregon University and send them your findings or a link to your observations:

southworth@sou.edu