Chicken Fat Mushroom
Suillus americanus
Also called american slippery jack, white pine bolete
A slender bright yellow bolete with a slimy, red-streaked cap and cottony veil fragments on the margin. It grows only with eastern white pine, often in large troops.
Overview
Suillus americanus is a small, vividly coloured slippery jack that carpets the ground under eastern white pine after summer rain. Its bright yellow, glutinous cap, streaked and blotched with cinnamon or reddish-brown fibrils, is unlike any other bolete in its range, and the ragged white cottony fringe of veil tissue hanging from the cap margin adds to the effect.
The species belongs to the yellow, veiled group of Suillus associated with five-needle pines, a group that includes the western Suillus sibiricus and several eastern Asian relatives. All share glutinous yellow caps, large radially arranged pores and a slender stature.
It is a gregarious fungus, and a good white pine stand may produce dozens or hundreds of fruiting bodies at once, scattered through needle litter and moss along the drip line of the trees.
How to identify it
Cap
3-10 cm across, conical to convex then flat and often broadly umbonate, slimy to glutinous when moist and shining when dry. The ground colour is bright yellow to ochre-yellow, overlaid with reddish-brown to cinnamon streaks, fibrils or patches, especially towards the centre. The margin is hung with soft, cottony white to yellowish veil fragments.
Pores
Large, angular and radially elongated, yellow at first and ageing to ochre or dull brown; they bruise cinnamon to reddish-brown where handled. The tube layer is adnate to slightly decurrent.
Stipe
3-9 cm tall but only 0.4-1.2 cm thick, slender, often curved, pale yellow and marked with scattered brown to reddish glandular dots that darken with age. A fugacious ring zone may be visible near the apex but soon disappears.
Flesh & spore print
The flesh is yellow and stains pinkish-brown to reddish-brown on cutting, particularly in the stalk. The spore print is cinnamon to dull brown.
Where and when it grows
Obligately mycorrhizal with eastern white pine (Pinus strobus), growing on soil, needle duff and mossy banks under both native stands and plantations. It is characteristically gregarious, appearing in scattered troops or dense clusters of many fruiting bodies.
Fruiting runs from early summer to autumn, responding rapidly to warm rain. The species is common across eastern and north-central North America wherever white pine occurs, and follows the tree into planted stands beyond its natural range.
Ecological role
The fungus forms ectomycorrhizal root tips on white pine, sheathing the finest roots and extending hyphae into the litter to mobilise nitrogen and phosphorus that the tree cannot reach unaided. In return it receives sugars, making the partnership essential to both organisms on thin, acidic forest soils.
Because the association is host-specific, spores and mycelial fragments of Suillus americanus travel with white pine seedlings, and the species establishes quickly in new plantations. Its thin-fleshed fruiting bodies decay within days, cycling nutrients back into the duff layer and supporting a range of fungus-feeding insects.
Similar species
Suillus sibiricus is closely related and similarly yellow and veiled, but occurs in western North America and Eurasia with other five-needle pines, and tends to be duller and more heavily streaked. Suillus spraguei shares the white pine host but has a dry cap densely clothed in brick-red woolly scales rather than a slimy streaked surface.
Suillus granulatus has a plain cinnamon-brown glutinous cap without any veil fragments on the margin and small round pores instead of large radial ones. Suillus salmonicolor is stockier, with a conspicuous thick gelatinous ring and salmon-tinted pores.