• Proposed
  • 2Under Assessment
  • 3Preliminary Assessed
  • 4Assessed
  • 5Published

Butyriboletus persolidus D. Arora & J.L. Frank

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Scientific name
Butyriboletus persolidus
D. Arora & J.L. Frank
Common names
Brown Butter Bolete
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Proposed by
Noah Siegel
Comments etc.
Noah Siegel

Assessment Notes

Taxonomic notes

Long called by the European species, Boletus appendiculatus Schaeffer (Thiers 1975, Arora 1986), the western North American species was described as a distinct species, and the group of closely related “butter boletes” were giving a new genus, Butyriboletus (Arora & Frank 2014).

Why suggested for a Global Red List Assessment?

Butyriboletus persolidus is a locally common butter bolete, growing with oaks in western North America.

Not enough data is available to assess trends, therefore I recommend listing it as Data Deficient (DD).

Geographic range

Coastal and coast range forests in California from Monterey County to Mendocino County, and in the Sierra Nevada foothills from the central and northern part of the range. Rare in the Pacific Northwest, where it has been reported from with Quercus garryana in the Willamette Valley of Oregon, and southern British Columbia, Canada.

Population and Trends

Population is fairly widespread; not enough data is available showing trends of this species.

Population Trend: Uncertain

Habitat and Ecology

Ectomycorrhizal with hardwoods, especially oaks (Quercus spp), fruiting in fall; especially in seasons with substantial early rainfall.

Temperate Forest


This species occurs across a fairly widespread area with oaks (Quercus spp.) and possibly other hardwoods. No threats have been directly linked to this species. This species tends to fruit in seasons with early fall rains; research into trends due to climate change, and the fall rainy season occurring much later in the year should be investigated.

Conservation Actions

No specific conservation actions have been identified with regards to this species.

Research needed

If climate change, and the later arriving seasonal rains affect this species.

Population size, distribution & trendsPopulation trends

Use and Trade

This species is edible, and is often collected for food.

Food - human


Arora, D. & Frank, J.L. 2014. Clarifying the butter Boletes: a new genus, Butyriboletus, is established to accommodate Boletus sect. Appendiculati, and six new species are described. Mycologia 106(3): 464-480.

Siegel, N. and Schwarz, C. 2016. Mushrooms of the Redwood Coast. Ten Speed Press: Berkeley, CA. 601 p.

Thiers, H.D. 1975. California Mushrooms—A Field Guide to the Boletes. Hafner Press: New York, NY. 261 p

Wood, M.G. and Stevens, F.A. 2020. MykoWeb; California Fungi. https://www.mykoweb.com/CAF/species/Butyriboletus_persolidus.html

Country occurrence

Regional Population and Trends

Country Trend Redlisted