Blackening Slimespike
(Gomphidius subroseus group)
Habitat: Under Douglas-fir (transplanted landscape grove, Lakeville, MN)
Cap: Smooth and strongly slimy when fresh, clay-pink to tan, darkening with age
Gills: Thick, waxy, slightly decurrent, eventually sooty, extending a short distance along the stem
Stem: Firm, glutinous, often darkening from the base upward
Spore print: Gray-black, radiating clearly on paper
Flesh: Whitish, staining darker over time, bright yellow stem
Even the best field guess can change under the light of a spore print.
Field Story
At first glance, this mushroom seemed like a Lactarius — its smooth tan cap and forest-floor habit matched the Argill Milkcap descriptions in the Audubon guide. But once the spore print appeared black-gray instead of yellowish, the identification slipped away.
The cap’s slimy texture and the slow darkening of the stem hinted at a Slimespike, a member of Gomphidius, a genus that often hides under conifers.
While Blackening Slimespike is most often recorded in the Pacific Northwest beneath Douglas-fir, the same host tree is sometimes planted ornamentally or for reforestation in Minnesota. This one was growing beneath a healthy stand of Douglas-fir — confirming that the partnership can extend well beyond its usual range.
Observations
- Spore Print: Rich gray-black fan pattern — classic Gomphidius.
- Cap Surface: Thick glutinous layer that can be peeled like a membrane.
- Gills: Darkened within hours of collection.
- Reaction: No milky latex observed — confirming it’s not Lactarius.
The forest is its own teacher: sometimes the answer only appears overnight on a sheet of paper.
References
- National Audubon Society: Mushrooms of North America (April 2023)
- Personal field notes, Lakeville MN (2025)
- Observations compared with Gomphidius subroseus and related species
- Distribution records from Pacific Northwest Mycological data, suggesting association with Douglas-fir
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