Suillus luteus (L.) Roussel - Slippery Jack

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Boletales - Family: Suillaceae

Suillus luteus - Slippery Jack

Suillus luteus, commonly known as Slippery Jack, is a most widespread summer and autumn fungus. It is the type species of the Suillus genus. The very slimy (when wet) cap surface is the origin of the common name, which in some countries is applied to several members of the genus Suillus.

This edible bolete is most often seen in large numbers beside paths in pine woods, and it is one of the boletes that has a distinctive ring, white at first but discolouring with age.

Suillus luteus in wet weather

Distribution

Suillus luteus is common and widespread throughout Britain and Ireland, always in or beside pine plantations. This bolete copes well in cold northern climes, and is very common in Scandinavia; it occurs also throughout the rest of Europe, Asia and North America.

Taxonomic history

When in 1753 Carl Linnaeus described this bolete he called it Boletus luteus. Later, in 1888, Lucien Quélet moved it from the Boletus genus and named it Ixocomus luteus. The currently accepted scientific name of the Slippery Jack, Suillus luteus, dates from a 1796 publication by the French mycologist Henri François Anne de Roussel (1748 - 1812).

Synonyms of Suillus luteus include Boletus luteus L., and Ixocomus luteus (L.) Quél.

Suillus luteus is the type species of the Suillus genus.

Suillus luteus in wet weather, Scotland

Etymology

The common name Slippery Jack (but please don't ask why Jack rather than Jill, Mary or Brian) is an obvious reference to the slimy nature of caps of this mushroom during wet weather - although they tend to become smooth and semi-matt and hence they are not particularly sticky during warm dry spells.

The specific epithet luteus seems obscure, because the Latin prefix lute- generally implies saffron yellow (the pores are yellow, but more lemon yellow than saffron); however, another meaning of luteus is dirty or muddy, and that may be the origin in this instance. If you have a reference source for this please let us know. Meanwhile the generic name Suillus is much more straightforward, coming from the Latin noun sus, meaning pig. Suillus therefore means 'of pigs' (swine) and is a reference to the greasy nature of the caps of all fungi in this genus.

Identification Guide

Cap of Suillus luteus, when wet

Cap

When wet, as shown on the left, the caps of this species are slimy; in hot sunny weather they dry to a smooth semi-matt finish.

Usually dark chestnut brown, but occasionally quite a lot lighter, the caps of Suillus luteus grow to between 5 and 10cm in diameter.

Pores of Suillus luteus

Tubes and pores

Beneath the cap, a white veil covers the lemon yellow pores of this bolete. The veil tears to leave an irregular ring on the stem and often pieces of veil hanging from the cap margin.

At first lemon yellow, the medium-sized round pores darken to a sienna-yellow with age.

Stem and ring of Suillus luteus

Stem

2 to 3cm in diameter and 5 to 10cm tall, the stem is pale straw-yellow at first, darkening with a dot pattern above the ring and with an irregular covering of brown longitudinal fibres near the base.

The large, floppy stem ring is white initially but usually develops a purplish tinge to its lower surface as the fruitbody matures.

 

Spores

Sub-fusiform, smooth, 8-10.5 x 3-3.5μm.

Spore print

Ochraceous or buff coloured.

Odour/taste

Not distinctive.

Habitat & Ecological role

Mycorrhizal; beneath conifers in damp, usually shaded places.

Season

August to November in Britain and Ireland.

Similar species

Suillus grevillei has a bright yellow-orange cap and angular pores; it occurs under larch.

Culinary Notes

Although not generally rated very highly, Slippery Jacks are reported to be edible when thoroughly cooked. To reduce the risk of an adverse reaction to these kinds of mushrooms some people have found it beneficial to discard the cap skin of all species from the Suillus genus.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

British Boletes, with keys to species, Geoffrey Kibby (self published) 3rd Edition 2012

Roy Watling & Hills, A.E. 2005. Boletes and their allies (revised and enlarged edition), – in: Henderson, D.M., Orton, P.D. & Watling, R. [eds]. British Fungus Flora. Agarics and boleti. Vol. 1. Royal Botanic Garden, Edinburgh.

BMS List of English Names for Fungi

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

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