Weeping Bolete

The Weeping Bolete is one of the most familiar members of Suillus, a genus of soft-fleshed boletes bound almost exclusively to conifers. Like its relatives it has a spongy tube layer rather than gills, a cap that turns greasy or glutinous in damp weather, and a comparatively soft, quickly decaying fruiting body. Within the genus it belongs to the ringless group: no membranous skirt is ever formed on the stalk, only a scatter of dark glandular dots.

What sets Suillus granulatus apart in the field is the behaviour of its young pore surface. In fresh, humid conditions the pale lemon tubes bead with pale, milky droplets that dry to rusty-brown spots, stippling the underside. This 'weeping' habit is shared with only a few close relatives and, combined with the absence of any veil, narrows identification quickly.

The species is enormously widespread, having travelled with planted pines across Europe, the Americas, Africa, Australasia and Asia. It is often among the first fungi to appear in young pine plantations, forming large troops along tracks and on thin sandy verges.

Cap

4-12 cm across, at first hemispherical then flattening. The surface is smooth, sticky to distinctly glutinous when wet and shining when dry, coloured cinnamon, ochre, rusty-tan or dull reddish-brown, often paler and yellower towards the margin. The skin peels easily. No veil fragments hang from the margin.

Pores

The tube layer is pale lemon-yellow when young, dulling to dingy yellow-ochre with age. Pores are small, round to slightly angular, and adnate to slightly decurrent. In young, moist specimens they exude conspicuous whitish to pale amber droplets that dry into rust-brown pinpoints.

Stipe

4-8 cm tall and 1-2 cm thick, cylindrical or slightly tapering, whitish at first then yellowing. There is no ring and no ring zone. The upper stalk, and often its whole length, is covered in tiny granular dots (glandulae) that begin pale and darken to brown or reddish-brown as the fruiting body matures.

Flesh & spore print

The flesh is soft, pale yellow, and does not change colour appreciably when cut, at most becoming a little more buff. The spore deposit is cinnamon to ochre-brown.

Strictly mycorrhizal with pines, favouring two-needle species such as Scots pine, Aleppo pine, Monterey pine and red pine. It thrives on light, sandy or calcareous soils, along forest rides, on roadside banks and in young plantations, frequently fruiting in large scattered troops.

The season runs from midsummer through to the first hard frosts, with peak fruiting in early autumn. Native across Europe and northern Asia and widespread in North America, it has followed forestry pines into the southern hemisphere and is now established in South America, southern Africa, Australia and New Zealand.

This is an ectomycorrhizal fungus: its hyphae sheathe the fine root tips of pine, supplying the tree with water, phosphorus and nitrogen drawn from a wide soil volume in exchange for sugars. The partnership is broad within the pine genus, which explains the species' success as a coloniser of newly planted stands.

Because it associates readily with young trees and tolerates poor, disturbed ground, Suillus granulatus is often one of the pioneer mycorrhizal fungi of pine afforestation. Its spores travel with nursery stock and soil, and its rapid, prolific fruiting makes it an important early contributor of fungal biomass in these systems.

Suillus luteus, the Slippery Jack, shares the glutinous brown cap but carries a large, persistent membranous ring on the stalk, with a purplish-brown band below it; the Weeping Bolete never forms a ring. Suillus brevipes has a darker chocolate cap and a notably short, stout stalk that is white and essentially free of glandular dots when young.

Suillus collinitus is very similar but shows a finely streaked, radially fibrillose cap and, most usefully, pink to rosy mycelial threads at the stalk base, whereas the Weeping Bolete has whitish base mycelium. Suillus punctipes has a duller grey-buff to olive-buff cap and a powerful sweet-spicy odour that the Weeping Bolete lacks.