A number of species are known in Europe. Fruitbody boletoid without or with partial veil, and then leaving a ring on the stipe. Cap in most species more or less viscid. Stipe solid.
Suillus caerulescens A.H. Sm. & Thiers
Known to me only from the literature. Fruitbodies with partial veil, soon disrupting and leaving a ring in the upper part of the stipe. Cap up to 15 cm, fibrillose or with fine appressed scales, orange-brown to reddish ochraceous, paler (to buff) towards the margin, usually distinctly viscid. Stipe cylindrical or slightly swollen below, solid, dirty whitish, straw or yellowish, darkening in the lower parts, below the tubes with a distinct whitish to somewhat yellowish ring. Flesh yellowish to yellowish-white, mostly unchanging when exposed to air, but blueing in the stipe base. Tubes short, decurrent, durty yellow to greyish yellow. Pores relatively large, angular, concolorous with the tubes, darkening when bruised. Smell not distinctive. Taste not distinctive. Spores 8–11 ´ 3–5 μm.
Habitat. Stands of Douglas’ fir (Pseudotsuga), with which tree the fungus is strictly mycorrhizal.
Distribution. North American fungus that has not yet been found in Europe but might be present and should be looked for.
Similarity. Compare with the other Pseudotsuga-associated species of the genus – Suillus lakei, S. ponderosus and S. imitatus. Due to its specific habitus Suillus caerulescens might superficially resemble some species of Suillus sect. Larigni – Suillus grevillei, S. tridentinus or S. viscidus. None of these however has blueing flesh.
Smith, A.H. & Thiers, H.D. 1964. A contribution toward a monograph of North American species of Suillus. Privately published, Ann Arbor.
Thiers, H.D. 1975. California mushrooms. A field guide to the boletes. Hafner Press, New York.