Weeping Bolete Identification Guide

The moment you spot it

You nearly always meet this bolete crouching. It appears in troops on thin, well-drained ground beneath pines, very often right where a path cuts through a plantation and the needle litter runs shallow. The first thing that registers is a scatter of low tawny domes, faintly greasy, sitting just proud of the needles. In wet weather the caps look varnished and collect a fringe of stuck pine needles, grit and fragments of bark; in dry spells they lose the wet shine and read simply as smooth and polished. Size within one troop varies wildly, with buttons the width of a thumbnail beside flattened 10 cm veterans whose margins have begun to warp and split.

That first impression, a slick tan cap over a lemon-yellow underside on a short pale stalk with no ring, is essentially the whole species. Even so it pays to walk through the characters in order, because Suillus is a genus in which three or four species can occupy the same stand of trees and separate only on small details.

Reading the cap

Pick a medium, fresh specimen rather than the biggest one. The cap runs roughly 4 to 12 cm across, convex at first, then broadly convex and finally almost flat, with a margin that starts incurved and straightens with age. Critically, the margin is clean: no shreds, flaps or cottony remnants hang from it, because this species is built without a partial veil.

Colour sits in the cinnamon to ochre-brown range, sometimes rusty, sometimes dull orange-brown, sometimes tending to pinkish-buff, and it is frequently uneven, streaked or mottled, with the outer third paler and more yellow-buff than the disc. The surface is smooth and viscid, genuinely glutinous after rain and merely tacky when damp. The cuticle peels away easily in a long strip, dragging its slime with it. Nothing on the cap is scaly, fibrillose-scurfy or dry-woolly. If your specimen has a dry, matted, felty cap, you are outside this species already.

Turning it over: the pore surface that weeps

Underneath there are pores, not gills. The tube layer is 4 to 8 mm deep, attached to the stalk or running very slightly down it, and it separates from the cap flesh fairly cleanly when you lever at it. Young material is a clean pale butter-yellow; with age it dulls to ochre and then to a tired olive-yellow. The pores themselves are small, roughly two to three per millimetre, round to faintly angular, and evenly sized rather than radially stretched.

On young caps in humid conditions the pore mouths bead with pale, milky droplets. This guttation is where the common name comes from, and it is one of the most useful confirmatory characters in the genus. The droplets do not last: they dry down to a stippling of cinnamon-brown dots across the pore surface, so even on an older specimen you can often see the historical record of the weeping as brown speckling. Handling or bruising dulls the pore surface to a brownish tone; there is no blue, no green and no rapid dramatic change.

The stalk and its glandular dots

The stipe is short and solid relative to the cap, about 3 to 8 cm tall and 1 to 2 cm thick, more or less equal or narrowing slightly downward. It is dry to the touch, in clear contrast to the cap, and never sheathed in gluten.

Ground colour is whitish, becoming distinctly yellow at the apex and often yellowish throughout in mature material. Bring a hand lens to the upper half and you will find the character that gave the species its epithet: a dense scatter of tiny glandular dots. These start pale and almost translucent, then darken through amber to cinnamon and finally brown, especially where fingers have been. They are dots, not a network. There is no raised reticulum, no ring, no ring zone, and no violaceous or vinaceous band anywhere on the stalk.

Base, flesh and colour change

Dig rather than pluck. At the very bottom you want to see the basal mycelium, and here it is white, sometimes with a faint cream tone, never rose or pink. Slice the whole fruiting body top to bottom. The flesh is thick and soft, whitish in the stalk and pale yellow immediately beneath the tubes and in the upper cap. On exposure to air it is essentially unchanging; the most you will usually see is a slow, faint buff or pinkish-brown discoloration low in the stalk. No blueing, no greening, no blackening. The smell is mild and vaguely fruity, nothing assertive.

Taking and reading a spore print

Cut the stipe flush and lay the cap pore-surface-down on paper. Use half white and half black paper if you have it, since a mid-brown deposit reads differently on each. The glutinous cap will glue itself to the paper, so many people work on foil, or rest the cap on two matchsticks to keep the pore surface just clear. Cover with a bowl or upturned cup to keep humidity up and drafts out, and leave it three to six hours; overnight is easier.

The print is a dull cinnamon to clay-brown, warm rather than olive and never rust-red, chocolate, pink or white. That colour alone rules out most of the gilled mushrooms sharing the habitat and separates this bolete from the yellow-printed Gyroporus. Under a microscope the spores are smooth, subfusiform and roughly 7 to 10 by 2.5 to 3.5 micrometres, pale yellow-brown in water.

Substrate, season and habitat

This is an ectomycorrhizal partner of pines, and in practice above all of two-needle pines: Scots, black, Corsican, maritime and Monterey pines are all classic hosts. It follows pine plantations far outside the tree's natural range, which is why it turns up abundantly in forestry blocks, shelterbelts, dune plantings and amenity pines on several continents.

It prefers well-drained soils, frequently sandy or lime-rich, and it is a creature of edges: track sides, banks, thinned young plantations and open woodland margins where litter is shallow. It never grows on wood. Fruiting runs from early summer through late autumn, in flushes a week or two after soaking rain, and the fruit bodies are strongly gregarious, often in loose arcs or rings that trace the edge of the mycelium. Finding one means finding twenty. If your collection came from under spruce, larch, oak or beech with no pine in sight, treat the identification as unproven.

Separating it from its closest look-alikes

Suillus luteus shares the same pines and the same gluten, but carries a conspicuous membranous ring, and above the ring the stalk is dotted while below it is often washed brownish-violet. Its cap is darker, a chocolate to purplish-brown. The ring settles it in one look.

Suillus brevipes has a squat, whitish stalk that is essentially free of glandular dots, at most acquiring faint smudges very late, and its cap is a darker uniform brown. It does not bead with droplets.

Suillus collinitus is the trap. Its cap is streaked with darker innate radial fibrils rather than mottled, its stalk dots are weaker, and, decisively, its basal mycelium is pink to rosy. Always excavate the base.

Suillus pungens of western North America begins with a strikingly mottled whitish-grey cap that only later turns olive and yellow-brown, and it carries heavy dots and copious droplets. The colour sequence is the giveaway.

Suillus americanus and Suillus placidus partner five-needle white pines instead. The first has a yellow cap streaked reddish and a cottony veil at the margin; the second is whitish to ivory with dots that stain vinaceous.

Suillus tomentosus and Suillus variegatus have dry, scurfy or felty caps rather than a glutinous skin, and their flesh flushes blue when cut.

Finally, Chroogomphus and Gomphidius also haunt pine plantations and can look superficially similar from above, but they have thick, decurrent gills instead of pores and dark grey to blackish spore deposits.

Field checklist

• Under two-needle pines, on well-drained ground, in troops
• Cap tan to cinnamon, viscid to glutinous, cuticle peeling easily, margin bare
• Pore surface pale yellow, beading with droplets when young, spotting brown with age
• Stalk short, dry, ringless, whitish to yellow, covered in glandular dots that darken
• Basal mycelium white, not pink
• Flesh whitish to pale yellow, no blueing
• Spore print dull cinnamon-brown