Phaeocollybia olivacea was described from a Type collection made in southwest Oregon, USA (Smith 1957).

The name Phaeocollybia olivacea has been misapplied to collections of the similar P. fallax, and P. pseudofestiva. All three can grow in close proximity; some collections identified as P. olivacea contain fruitbodies of two or more of these species.

Phaeocollybia olivacea is a widespread species in Oregon and California, USA, with ~150 known locations.

Most collections come from mid to late seral stage and old growth forests; this species appears to be able to colonize forest at a younger age than most Phaeocollyia species. Based on the number of known locations, and recent reports, this species appears to be locally common where suitable habitat exist, but overall habitat has, and continues to decline. However, it may be common enough, and have enough of a habitat range to qualify as a Least Concern (LC) listing.

Known from Santa Cruz County, California north in coastal and Coast Range forests, through the Siskiyou Mountains, and Oregon coast and Coast Range, Oregon Cascade foothills, and rarely in the Sierra Nevada of California.

Population is widespread, and appears stable. Currently known from >150 locations in California and Oregon.Although it has a preference for late seral stage and old growth forests, it is not restricted to such sites, and appears to be able to colonize forest at a younger age than most Phaeocollyia species. Based on the number of known locations, and recent reports, this species appears to be locally common, and stable.

Ectomycorrhizal with conifers and possibly hardwoods; it has a preference for mid to late seral stage and old growth forests. Often fruiting in arcs and rings, less often solitary or scattered, typically in areas with thick duff. Fruiting in fall and early winter.

Continued loss of mature and old growth forests, due to logging and fires in northern California and the Pacific Northwest. Sudden Oak Death (Phytophthora ramorum) has killed large swaths of Tanoak in coastal California; this may have a long term negative effect of suitable habitat.

This is a ectomycorrhizal fungus species dependent on living host trees for viability. The major threat to this species and its co-occurring co-generic brethren is habitat destruction, via the logging of old-growth forests to which this species has a preference for. The extent of old growth forest in the Pacific Northwest of North America has declined 90% in the last century (Society of American Foresters 1984, Haynes 1986).

Climate change and droughts, along with forest management practices has made western forests highly susceptible to stand replacing forest fires. Fire is big threat to this species’ populations. A stand replacing fire could severely degrade and/or diminish its current range. Logging and machine clearing of understory vegetation should be limited in mature and old growth forest in areas where this species might occur.

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

No specific research is needed with regards to this species.

None known.

Norvell, L. and Exeter, R.L. 2009. Phaeocollybia of Pacific Northwest North America. US Department of Interior, BLM: Salem, OR. 229 p.

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

Siegel, N., Vellinga, E.C., Schwarz, C., Castellano, M.A. and Ikeda, D. 2019. A Field Guide to the Rare Fungi of California’s National Forests. Bookmobile: Minneapolis, MN. 313 p.

Smith, A.H. 1957. A contribution toward a monograph of Phaeocollybia. Brittonia 9: 195-217.