This symbiosis occurs with various species of pine, and the fruit bodies (or mushrooms) of the fungus appear scattered or in groups on the ground near the trees.

The mushroom's dingy yellow to brownish cap is rounded to flattened in shape, slimy when wet, and grows up to 9.5 cm (3.7 in) wide.

Young specimens are covered with a grayish, slimy partial veil that later ruptures and leaves a sheathlike ring on the stem.

The species was first described scientifically by American mycologist Charles Christopher Frost in 1874 as Boletus salmonicolor, based on specimens he collected in the New England area of the United States.

Palm and Stewart concluded that a study of specimens from various areas of their geographical ranges would be needed to fully resolve the taxonomy of these related species.

[16] In their 2000 monograph of North American boletes, Alan Bessette and colleagues list the two taxa separately, noting that the range of S. cothurnatus is difficult to determine because of confusion with S. salmonicolor.

[17] In a molecular analyses of Suillus phylogeny, based on the internal transcribed spacer, S. salmonicolor (as S. subluteus) and S. intermedius clustered together very closely, indicating a high degree of genetic similarity.

Glandular dots are made of clumps of pigmented cells, and, unlike reticulation or scabers (small visible tufts of fibers that occur on the stems of other Suillus species), can be rubbed off with handling.

[12] The surface of the cap, when applied with a drop of dilute potassium hydroxide (KOH) or ammonia solution (chemical reagents commonly used for mushroom identification), will first turn a fleeting pink color, then dark red as the flesh collapses.

They appear hyaline (translucent) to yellowish in a dilute solution of KOH, and cinnamon to pale ochraceous when stained with Melzer's reagent.

These bundles are underlain by a layer of gelatinous, hyaline, vertically oriented and parallel hyphae that are shaped like narrow cylinders.

[8] The mushroom is edible, but removal of the slimy cap cuticle and partial veil is recommended to avoid possible gastrointestinal upset;[20] similarly, the 1992 field guide Edible Wild Mushrooms of North America recommends the removal of the tube layer before preparation, as it can become slimy during cooking.

It may be distinguished by a lighter-colored cap, cream to yellowish or pale ochraceous flesh, and a ring that is neither as thick nor as wide as S. salmonicolor.

[27] Although it has not been definitively established whether S. cothurnatus is a distinct species, several characteristics have been reported to differentiate it from S. salmonicolor: a thinner, less rubbery veil that usually lacks a thickened cottony roll at the base; glandular dots on the stem that consist of bundles of multiseptate hyphae in a parallel arrangement ending in an even row of large, sterile cystidia (60–140 μm long) that resemble basidia; and small hyaline cystidia shaped like swollen bottles with narrowed bases.

[38] S. salmonicolor is one of several ectomycorrhizal species that have "traveled the thousands of kilometers from a mainland to Hawaii in the roots and soil of introduced seedlings.