Suillus quiescens was described from collections made in California, USA (Bruns et al. 2010).

Suillus quiescens is a widespread, but rarely reported Suillus in California and Oregon. Currently known from about 15 locations from fruit bodies, and a few populations only from root tip sequences and environmental samples. This species may be persistent in a soil spore bank, growing with pine seedlings and fruiting with young pines post forest fires or other disturbance.

This species could be listed as Data Deficient (DD) based on the scarcity of knowledge of range and ecology; or based on the widespread nature, and the likelihood of it being under-reported (due in part to misidentifications), as Least Concern (LC).

Currently known from disjunct populations in Califronia and Oregon, USA; from the Channel Islands in the south, eastern Sierra Nevada in the east, and central Oregon coast in the north. However, being a recently described species, and still often misidentified as Suillus brevipes, distribution limits are not yet fully known. Based on known habitat, it is likely far more widespread than currently known. 

Introduced to New Zealand, where it grows with the non-native Pinus radiata.

Population is widespread, but may be an infrequent fruiter in many areas, and may be present in areas as a spore bank in the soil (Bruns et al. 2019). Currently known from ~15 fruiting locations (Mushroom Observer 2021, iNaturalist 2021), but expected to be more common than currently reported. Data to assess trends of this species is lacking.

Ectomycorrhizal with two- and three-needle pines, especially young Pinus muricata and P. radiata. But also with P. contorta on the northern California and Oregon coast, and based on environmental samples, likely with P. ponderosa and P. jeffreyi as well. Suillus quiescens may be an infrequent fruiter in many areas, and may be present in areas as a spore bank in the soil (Bruns et al. 2019), colonizing pine seedlings post forest fires. More data is needed on ecology of this species.

Native stands of Pinus radiata and P. muricata are under threat from development, and a change in fire regime. Pinus ponderosus has suffered die-back from drought stress in the Sierra Nevada foothills. However, these threats are likely at a scale that has little affect on the overall population.

Protect and manage coastal Pinus muricata and P. radiata forests in California.

Track population trends, and gain a better understanding of ecology of this species.

This species is edible; and it, and closely related Suillus are occasionally indiscriminately collected for food.

Bruns, T.D., Grubisha, L.C., Trappe, J.M., Kerekes, J.F. and Vellinga, E.C. 2010. Suillus quiescens, a new species commonly found in the spore bank in California and Oregon. Mycologia 102(2): 438-446.

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

Mushroom Observer. 2021. Available at: http://www.mushroomobserver.org

Woods, M. and Stevens, F. 2021. MykoWeb. The Fungi of California. https://www.mykoweb.com/CAF/species/Suillus_quiescens.html