Assessment Notes

Justification

Lactarius rufulus is a common milk cap in southern and central California, USA, found in oak woodlands. No decline has been observed although localized threats may exist. It is listed as Least Concern (LC).

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Taxonomic notes

This species was described from a collection made at Stanford University, California, USA (Peck 1907).

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Geographic range

This species is known from California, USA. It occurs from San Diego County north into Sonoma County in coastal and coast range oak woodlands, and around the southern and central portions of the Central Valley in similar habitat. It is likely to also occur in Baja California, Mexico.

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Population and Trends

Lactarius rufulus is very common, occurring over a wide area. Much of its habitat is around urban areas, including some subjected to development, but likely not at a scale that would affect the population overall.

Population Trend: Stable

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Habitat and Ecology

This species is ectomycorrhizal with oaks (Quercus spp.), especially Coast Live Oak (Quercus agrifolia). It is more common in hotter, drier oak woodlands (southern California). Fruiting occurs from fall into spring; depending on seasonal rainfall.

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Threats

Urban development is a potential threat, but not at a scale to affect the population overall. Loss of oak woodlands is an additional threat.

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Conservation Actions

No specific conservation actions are needed with regards to this species, and no specific research is currently needed either.

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Use and Trade

This species is edible, and occasionally collected for food.

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Source and Citation

Siegel, N. 2021. Lactarius rufulus. The IUCN Red List of Threatened Species 2021: e.T195922522A195927765. Accessed on 22 November 2025.

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• Country occurrence