Assessment Notes

Justification

Leccinum arbuticola is a bolete which grows with Madrone and Manzanita. Most records come from the Nevada City-Grass Valley area in the Sierra Nevada foothills of California, with other scattered locations in the Sierra Nevada foothills.

Currently it is known from 31 collections, from nine sites but all but three of the of the records are over 30 years old. However, this species comes from an area which has been poorly surveyed for fungi in the past 40 years. Efforts should be made to locate this species, and assess trends. As it is currently not possible to estimate if this species is under severe decline, or is severely under-sampled, is more common and occurs over a much wider distribution throughout its host plants' range, it is assessed as Data Deficient.

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Taxonomic notes

This species was described based on collections made in Nevada County, California, USA (Thiers 1975).

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Geographic range

Currently known from California, USA, this species has been reported from the Sierra Nevada foothills, with a single record from interior Mendocino County.

Reports from Mexico (Mycoportal 2024) likely represent a distinct species, and are not included in this assessment.

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Population and Trends

This species is currently known from 31 collections, from nine localities; however, all but three of those records are older than 30 years (Mycoportal 2024). It is not clear if the lack of recent collections represents a lack of people looking for, and correctly identifying, this species versus a dramatic decline in its population. Habitat dominated by Pacific Madrone (Arbutus menziesii) and Manzanita (Arctostaphylos spp.) is widespread, but more data are needed to identify the additional factors comprising suitable habitat for this species. The zone this species occurs in is subjected to sporadic rainfall, and these areas can go years before receiving adequate rainfall to produce sporocarps. Taking a precautionary view, it is assumed that the species is in decline.

Population Trend: Decreasing

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Habitat and Ecology

This species is ectomycorrhizal with Pacific Madrone (Arbutus menziesii) and Manzanita (Arctostaphylos spp.), with scattered fruitbodies produced in fall and early winter, typically covered with leaves and debris.

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Threats

Too little is known regarding this species’ distribution and details of its habitat preferences to properly assess possible threats. Habitat dominated by Manzanita is widespread, but more data are needed to identify the additional factors comprising suitable habitat for this species.

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Conservation Actions

No specific conservation actions can be identified with regards to this species at this time. Targeted surveys for this species are needed as is a better understanding of its habitat restraints. Modern taxonomic work on Leccinum in California is also needed.

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Use and Trade

Most Leccinum species are edible; and being difficult to identify past genus level, many are indiscriminately eaten.

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Source and Citation

Mueller, G.M. & Siegel, N. 2025. Leccinum arbuticola. The IUCN Red List of Threatened Species 2025: e.T272237296A272240930. Accessed on 23 November 2025.

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• Country occurrence