Butyriboletus querciregius is a pink-capped butter bolete, growing with coastal oaks in California, Oregon, Washington in the USA and possibly into southern British Columbia, Canada. This species occurs over a widespread range, and based on the number of observation in iNaturalist, it does not appear to be rare.  Local threats may be negatively impacting its population size, but over its distribution it is could be relatively stable. The potential future impact on its population due to increasing drought and Sudden Oak Death should be followed.  For now, it is assessed as Least Concern.

For many years, this species was one of three western North American ‘cryptic’ species being called Boletus regius Krombholz (Thiers 1975, Arora 1986).  Arora & Frank (2014) described the three species, and erected the genus Butyriboletus for the group of closely related ‘butter boletes’.

Butyriboletus querciregius is a pink-capped butter bolete, growing with oaks in USA.

This species occurs over a widespread range, but is known from a limited number of records, and not enough data is available to assess trends, therefore I recommend listing it as Data Deficient (DD).

Growing with oaks (Quercus spp) in coastal and coast range forests in California from San Diego County northward, and in the Sierra Nevada and Cascade Range foothills into the Pacific Northwest, where it occurs with Oregon White Oak (Quercus garryana) in the Willamette Valley of Oregon, and Columbia River Valley in Washington; and possibly into southern British Columbia, Canada.

Population occurs over a widespread area, with most over 160 iNaturlaist records, with a majority from California (iNaturalist 2024). Being a recently described species (Arora & Frank 2014), in the ‘Boletus regius’ complex, pre-2014 records need extra scrutiny.

Ectomycorrhizal with oaks (Quercus spp.), especially Coast Live Oak (Quercus agrifolia) in California, and Oregon White Oak (Quercus garryana) in the Pacific Northwest. Fruiting in fall, especially in seasons with substantial early rainfall.

This species occurs across a fairly widespread area with oaks (Quercus spp.). Overall, the habitat has threats from urban development leading to loss of habitat and invasive plants, especially grasses growing in oak woodlands. Sudden Oak Death caused by Phytophthora ramorum is threat to its host and may negatively impact its population. 
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.

Control invasive plants in oak woodlands and spread of Sudden Oak Death.

More data on populations and trends of this species; is climate change affecting this species.

This species is edible and is often collected for food.

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.

iNaturalist. 2021. http://www.inaturalist.org

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