Lactarius fumosus

Taxonomy

• Kingdom: Fungi
• Phylum: Basidiomycota
• Class: Agaricomycetes
• Order: Russulales
• Family: Russulaceae
• Genus: Lactarius
• Species: Lactarius fumosus (Pers.) Fr., 1838

Common name

• Smoky milkcap (used in some European field guides)

Description

• Cap: 5–12 cm in diameter; initially convex becoming broadly depressed; surface dry, smooth to slightly fibrillose, colored smoky‑grey to brownish‑grey, often with a faintly hygrophanous rim.
• Gills: Decurrent, crowded, pale cream to ochre; edges sometimes slightly pinkish.
• Stipe: 4–9 cm long, 0.8–1.5 cm thick; cylindrical, often slightly tapering toward the base; same colour as the cap or slightly paler.
• Flesh: White, firm, not bruising.
• Latex: White when the flesh is cut, turning bright yellow within a few minutes; the colour change is a diagnostic feature.
• Spore print: Creamy white.
• Spores: Ellipsoid, 7–9 µm × 5–6 µm, ornamented with prominent warts and ridges forming a reticulum.

Habitat and distribution

• Lactarius fumosus is a mycorrhizal species, primarily forming associations with birch (Betula spp.) and occasionally with other deciduous trees such as oak (Quercus).
• It fruits on the forest floor in summer to early autumn.
• Reported from temperate regions of Europe (including the British Isles, Scandinavia, Central and Eastern Europe) and parts of North America, especially the northeastern United States and southeastern Canada.

Edibility

• Generally regarded as inedible or of low culinary value. The latex’s rapid colour change to yellow, along with a mildly bitter taste, makes the species undesirable for consumption.

Similar species

• Lactarius rufus – reddish‑brown cap, latex does not turn yellow.
• Lactarius semisanguifluus – has a more vivid orange–red latex that also changes colour but differs in cap hue and habitat preference.

Conservation

• Not listed on major international red‑list assessments. It is considered locally common in suitable habitats but may be locally scarce where birch woodland has declined.

References

• Standard mycological field guides (e.g., Mushrooms of Europe by Dirk Boertmann, 2018).
• Peer‑reviewed fungal taxonomic databases such as Index Fungorum and MycoBank, which record the authority and synonymy of Lactarius fumosus.