Extensively detailed as Boletus “marshii” in Mushrooms Demystified (Arora 1986), later formally described as Caloboletus marshii (Frank 2014).

Caloboletus marshii is a widespread bolete in western United States. Most populations are known from the range of its preferred ectomycorrhizal partner, Coast Live Oak. Also occasionally with other oak species around the Central Valley and Sierra Nevada foothills in California, and scattered populations in the Willamette Valley of Oregon, and Columbia River valley in southern Washington.

Population is widespread, and no decline has been observed. We recommend it should be listed as Least Concern (LC).

Occurring from southern California, USA into Humboldt County in coastal/Coast range forests, typically with Coast Live Oak (Quercus agrifolia); scattered populations inland around the Central Valley, and the Sierra Nevada foothills of California, and more rarely with Quercus garryana in the Willamette Valley of Oregon, and Columbia River valley into Washington.

Population is widespread, and appears stable; no decline has been noted.

Ectomycorrhizal with oaks (Quercus spp.), especially Coast Live Oak (Quercus agrifolia). Typically fruiting in late summer or early fall, even before the seasonal rains.

Urban development leading to loss of habitat. Invasive plants, especially grasses growing in oak woodlands.

Control invasive plants in oak woodlands.

No specific research is needed with regards to this species.

Arora, D. 1986. Mushrooms Demystified. Ten Speed Press: Berkeley, CA. 959 p.

Frank, J.L. 2014. Nomenclatural Novelties. IndexFungorum No. 194: 1.

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