Never eat a wild mushroom identified only from a website, a book or an app. Have every find checked in person by an expert, such as a mycological society.
Identification
The slippery jack is a medium-sized bolete with a convex to flat cap in shades of chestnut, purplish brown or chocolate. In wet weather the cap is covered with a thick, glutinous slime; when dry it is shiny and often streaked. Instead of gills, the underside has small, round, yellow pores that age to olive-yellow and do not turn blue when pressed.
The most distinctive feature is the ring. Young specimens have a membranous partial veil covering the pores; as the cap opens it tears and leaves a large, floppy ring on the stem that is whitish at first and becomes brownish or violet-tinged on the underside. Above the ring, the stem is pale yellow with small glandular dots; below it, it is whitish to brownish. The flesh is soft, white to pale yellow and does not change colour on cutting.
The spore print is ochre to clay brown, and the spores are smooth and spindle-shaped, as in many boletes.
Habitat and ecology
Suillus luteus is an ectomycorrhizal partner of pines, especially two-needled species such as Scots pine (Pinus sylvestris), Austrian pine and, where planted, Monterey pine (Pinus radiata). It grows in grass and needle litter at the edges of pine woods, in young plantations, parks and gardens, often in large numbers, from late summer until the first frosts.
Native to Eurasia, it has been carried around the world with pine seedlings and is now common in pine plantations of the Southern Hemisphere, for example in South America, southern Africa and Oceania. It is often used as an example of how mycorrhizal fungi help introduced trees establish.
Uses and importance
The slippery jack is a popular edible in many countries, collected in quantity in pine plantations. The slimy cap skin is usually peeled off before cooking, and many cooks also remove the spongy pore layer in older specimens. It is best sautéed, added to soups and stews, or dried; drying improves texture and flavour. In some regions it is also pickled or preserved.
Because it is easy to recognise, abundant and associated with planted pines, it is an important wild food in several countries where pines were introduced.
Safety and edibility
Suillus luteus is edible when correctly identified and cooked. Never eat a wild mushroom based on a website or photo: have every collection confirmed in person by an expert, for example at a mycological society or by a trained mushroom adviser. Remove the slimy cap skin, cook thoroughly and start with a small portion, as the species causes digestive upsets (mainly a laxative effect) in some people; handling the slime can also irritate sensitive skin.
It has no deadly look-alikes in pine woods if all features are checked, but beginners should be aware that dangerous Amanitas also grow under pines, so every mushroom must be checked individually and never collected in a mixed batch without inspection.
If you suspect mushroom poisoning, call 999 in an emergency or NHS 111 for urgent advice straight away, even before symptoms appear, and keep the remains of the mushrooms.
Look-alikes
Suillus granulatus (weeping bolete) grows in the same habitat but has no ring and exudes milky droplets from the young pores; it is also edible. Suillus collinitus has a pinkish mycelium at the stem base and no ring. Suillus grevillei (larch bolete) has a yellow to orange cap and grows only under larches. Chalciporus piperatus is small, with rusty pores and a very peppery taste.
In the UK
The slippery jack is common in Britain and Ireland under pines, especially Scots pine, in plantations, heaths and parks, from late summer to late autumn. Its slimy brown cap and large ring are easy to recognise.
It is edible once the slimy skin is peeled off and the spongy pores removed, though some people react to it. Pick sparingly and only for your own use; in Scotland, customary picking for personal consumption is accepted, while commercial collection needs the landowner's permission.