The woolly cap margin, pinkish tones in the cap, acrid latex, and association with birch are reliable field characteristics to help identify L. torminosus.
However, there are several hairy Lactarius species with which it is often confused, and sometimes examination of microscopic characteristics is necessary to distinguish between them.
The closely related L. torminosulus is a dwarf version of L. torminosus, an arctic species associated with the birches Betula nana or B. glandulosa.
Immature fruit bodies of L. scrobiculatus resemble L. torminosus, but they have a white latex that soon turns yellow upon exposure to air, and their stems have shiny depressed spots.
The caps of the poorly known species L. cilicioides are not zonate, and its spores are smaller.
L. pubescens is physically quite similar, but can be distinguished by its paler color and smaller spores (6.0–7.5 by 5.0–6.5 μm).
L. controversus has a cap margin that is not as hairy, whitish to cream-colored gills, and larger spores measuring 7.5–10 by 6–7.5 μm.
L. mairei has a coloration similar to L. torminosus, but is rarer and typically found associated with oak trees on calcareous soil.
Known only from North Carolina and western Canada, L. subtorminosus was named for its similarity to L. torminosus.
It can be distinguished by its mild-tasting latex and smaller, roughly spherical spores measuring 5.5–7 by 5.5–6.5 μm.
The woolly cap margin, pinkish tones in the cap, acrid latex, and association with birch are reliable field characteristics to help identify L. torminosus. However, there are several hairy Lactarius species with which it is often confused, and sometimes examination of microscopic characteristics is necessary to distinguish between them. The closely related L. torminosulus is a dwarf version of L. torminosus, an arctic species associated with the birches Betula nana or B. glandulosa. Immature fruit bodies of L. scrobiculatus resemble L. torminosus, but they have a white latex that soon turns yellow upon exposure to air, and their stems have shiny depressed spots. The caps of the poorly known species L. cilicioides are not zonate, and its spores are smaller. L. pubescens is physically quite similar, but can be distinguished by its paler color and smaller spores (6.0–7.5 by 5.0–6.5 μm). L. controversus has a cap margin that is not as hairy, whitish to cream-colored gills, and larger spores measuring 7.5–10 by 6–7.5 μm. L. mairei has a coloration similar to L. torminosus, but is rarer and typically found associated with oak trees on calcareous soil. Known only from North Carolina and western Canada, L. subtorminosus was named for its similarity to L. torminosus. It can be distinguished by its mild-tasting latex and smaller, roughly spherical spores measuring 5.5–7 by 5.5–6.5 μm.
Lactarius torminosus