Assessment Notes

Justification

Lactarius indigo is widely distributed and commonly found in North and Central America into montane Colombia and temperate Asia. It forms ectomycorrhizal associations with a number of different tree species, primarily species of Quercus and Pinus. It is assessed as Least Concern.

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Geographic range

Lactarius indigo is fairly widespread in its distribution, from Asia (China, Japan and India) to most of North America and Central America along the gulf coast, Mexico, Costa Rica and Guatemala (Wang 2000, Sharma and Das 2002, Upadhyay and Kaur 2004, Mueller et al. 2006) with its southernmost distribution found in the Humboldt oak cloud forests of Colombia (Winkler 2013). In Europe, it has only been reportedly sighted in the UK and southern France (Marcel 1988) but its identity needs to be confirmed and it is excluded from this assessment.

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Population and Trends

Lactarius indigo is a well-known edible and common fungus with a vast population in North and Central America into montane Colombia. It is also reported from temperate Asia. Given its distribution and abundance, the population is stable. It is described to be “occasional to locally common” in terms of its frequency of appearance (Roody 2003) in the Appalachian Mountains of the United States. It has a seasonal harvest time; fruit bodies are often widely collected during the rainy season between June and September.

Population Trend: Stable

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Habitat and Ecology

Lactarius indigo is mutualistic, forming ectomycorrhizal associations with a number of different tree species, primarily species of Quercus and Pinus. The species commonly grows scattered or in groups living symbiotically in mycorrhizal associations with oak and pine woods in North America (Hesler and Smith 1979) but in Mexico, it is associated with Mexican Alder (Alnus jorullensis), American Hornbeam (Carpinus caroliniana), American Hop-hornbeam (Ostrya virginiana) and Liquidambar styraciflua (Montoya and Bandala 1996). In Costa Rica and Colombia, it has been found to be associated with several native oaks of the genus Quercus (Halling 2009). It has also demonstrated considerable variability in its appearance in different environments. As a mycorrhizal fungus, this change of host plant and appearance in different ecosystems could be the result of migration and its adaptations to new environments (Wu and Mueller 1997) or that this is a species complex in need of revision.

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Threats

The species is not currently undergoing any reported declines.

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Conservation Actions

Old forests containing the trees with which Lactarius indigo grows should be protected, and wildfires should be prevented. It should be ensured that hikers or foragers are aware of the impact they can bring upon mycological and ecological systems. Additionally, a rigorous taxonomic study of specimens from throughout its range and tree associations should be undertaken to determine if this is a species complex.

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Use and Trade

This species is often sold in local farmer markets in many countries including Guatemalan, China and Mexico (Montoya and Bandala 1996, Wang 2000, Flores et al. 2005). Its bright blue pigment has been used for a variety of uses, including as a basis for fluorescent pigments.

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Source and Citation

Mueller, G.M. 2025. Lactarius indigo. The IUCN Red List of Threatened Species 2025: e.T260333143A277419154. Accessed on 20 November 2025.

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• Country occurrence