Fungus · GBIF taxon 5243506
inky mushroom
Agaricus placomycesAlso known as Inky Agaricus, Flat-top Agaricus
Emerging from rich woodland soil and decaying leaf litter, this striking mushroom displays a flattened white cap scattered with fine dark grey or brown scales. When cut or bruised at the base of the stalk, the flesh flashes bright yellow before slowly fading to brown while releasing a distinct ink or phenol odor. It plays a vital role in North American forest ecosystems by decomposing organic litter into nutrient-rich humus.
FungusToxicWoodland
1 / 7—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Diet & prey
- Decaying organic matter
- Leaf litter
- Wood debris
Predators
- Fungus gnats
- Slugs
- Rodents
ThreatsHabitat degradation and soil contamination
HabitatsDeciduous forests, mixed woods, landscaped parks
Life spanPerennial mycelium with short-lived seasonal mushrooms
Size / weightNot available
Classification
- OrderAgaricales
- FamilyAgaricaceae
- GenusAgaricus
- SpeciesAgaricus placomyces
Range data is not available yet.
Interaction riskHigh
- Low
- Moderate
- High
- Very high
- Why interaction risk is high
- Causes severe gastrointestinal distress if eaten, and many wild fungi have toxic look-alikes; never ingest.
- Why it is dangerous
- Contains phenol and toxic compounds that trigger severe gastrointestinal distress, including acute vomiting and abdominal pain.
- How to recognize a risky encounter
- Look for a dark-scaled cap, chocolate-brown gills at maturity, and stem flesh that turns yellow when scratched while smelling like ink.
- What to do
- Observe and photograph freely, but do not harvest for food or ingest any part.
Responsible observation
- Odor Check: Gently scratch the stem base to detect an unpleasant ink or phenol smell.
- Observe Staining: Watch for a temporary yellow bruise at the base of the stem when cut.
- Spore Print: Collect mature spores on white paper to reveal a chocolate-brown print.
Toxic Look-alike Velella / CC BY-SA 3.0 · cc-by-sa
Edible Look-alike (c) anonymous, some rights reserved (CC BY-SA) · cc-by-sa
Eurasian Counterpart 
Close Relative (c) Adam J. Searcy, some rights reserved (CC BY), uploaded by Adam J. Searcy · cc-by
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