• Proposed
  • Under Assessment
  • Preliminary Assessed
  • LCAssessed
  • 5Published

Suillus caerulescens A.H. Sm. & Thiers

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Scientific name
Suillus caerulescens
A.H. Sm. & Thiers
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Category
Proposed by
Noah Siegel
Noah Siegel
Anders Dahlberg

Assessment Notes


Suillus caerulescens is a common ectomycorrhizal fungus, associated with Douglas-fir (Pseudotsuga menziesii) in western North America. There is no evidence of decline: it can be locally abundant where suitable habitat exists. Therefore, it is assessed as Least Concern (LC).

Taxonomic notes

Described by Smith & Thiers (1964). Suillus imitatus var. imitatus is a synonym (Nguyen et.al., 2013).

Why suggested for a Global Red List Assessment?

Geographic range

Widespread across western North America, roughly following the coastal and Sierra Nevada distribution of Douglas-fir (Pseudotsuga menziesii var. menziesii) in California, USA, north through Oregon and Washington into southern British Columbia, Canada. It also occurs in the Rocky Mountains in southern British Columbia and Alberta, Canada, south through Idaho and Montana, and scattered through the mountains in Colorado, Utah, New Mexico and Arizona with Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca). Distribution records in the Rocky Mountains are sparse in comparison to Pacific states collections. Non-native populations occur in Douglas-fir plantations in Argentina.

Population and Trends

The population size is large, occurring over a widespread area, and is stable. There is no indication of any decline.

Population Trend: Stable

Habitat and Ecology

Ectomycorrhizal, associated with Douglas-fir. Very common, especially in young forests.

Temperate Forest


There are no major threats to this species. It is common, and found with young to mature trees, in both urban and forested habitats.

Conservation Actions

Research needed

Use and Trade

This species is edible, but rarely collected for food.

Food - human


Nguyen, N., J.F. Kerekes, E.C. Vellinga and T.D. Bruns. 2013. Synonymy of Suillus imitatus, the imitator of two species within the S. caerulescens/ponderosus complex. Mycotaxon 122: 389-398.

Nguyen, N., E.C. Vellinga, T.D. Bruns & P. Kennedy. 2017. Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa. Mycologia 108: 1216–1228.

Smith AH, Thiers HD. 1964. A Contribution Toward a Monograph of North American Species of Suillus (Boletaceae). Ann Arbor, Michigan: Lubrecht & Cramer.

Country occurrence

Regional Population and Trends

Country Trend Redlisted