Public Description of Suillus Gray

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Name: Suillus Gray
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Description status: Unreviewed

Taxonomic Classification:

Domain: Eukarya
Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Order: Boletales
Family: Suillaceae

General Description:

Bolete with viscid cap and/or partial veil and/or glandular dots on stem; olive- to dark-brown spore print. Almost all Sullus species are Pinaceae associates.
Cap can be dry to strongly viscid, smooth to strongly fibrillose or scaly.
Partial veil can: sometimes leave an annulus on the stem; be cottony, viscid, or elastic-membranous; sometimes leave tissue at cap margin and thus appendiculate.
Pores often appear somewhat radially elongated/radially arranged, mouths often slightly angular or irregular in appearance.
Stipe with or without small, slimy glandular dots.

Diagnostic Description:

Structures of the fungi in this genus in common with members of the family Boletaceae including the presence of a cylindrical stipe, fleshy pileus, soft context and tubular hymenium. Pileus surface viscid to glutinose and glabrous, slimy and sticky when moist or dry and fibrillose-squamulose, the fibrils or scales superimposed above a gelatinized layer, more rarely innate, detersile or not, sometimes with appendiculate remnants. Microscopically an ixotrichodermium or a trichodermium, or also a two-layered cuticle consisting of an upper trichodermal and a lower gelatinous layer.
Context white or pale yellow, unchanging or staining pale reddish or turninggreenish-blue by autooxidation. Hymenophore adnate to adnexed, sometimes decurrent, whitish, grey, yellow, orange or pale cinnamon brown, seldom bruising bluish or greenish. Pores small to wide, occasionally boletinoid. Stipe solid, dry or glutinous, veil present or absent, often forming an annulus or merely a velar appendiculation on the margin of the pileus, typically with but also without glandular dots or smears. Bilateral hymenophoral trama boletoid. Spores smooth, elongate, short fusoid, usually cinnamon brown or chocolate brown in mass, sometimes with olivaceous tinge. Hymenial cystidia rather large and mostly covered by a colored incrustation, usually clustered, with amorphous brown pigmentation at the base. Clamp connections absent.
Distributed mostly in the northern temperate hemisphere and southward into the tropics to the southern limit of Pinaceae. Some species introduced adventitiously with pine trees in pine plantations outside of the indigenous area of Pinaceae; thus frequently occurring with transplanted Pinaceae. Species in the genus associated especially with members of the genera Pinus, Larix and Pseudotsuga, but also known with Betula spp. and Salicaceae; most species obligately mycorrhizal (SINGER 1986, ŠUTARA 1987 a, 2005, KLOFAC 2007, HALLING 2013); the strict affiliation to accompanying trees often overestimated (KRETZER & al. 1996, WU & al. 2000).2


The genus is extremely widespread, almost everywhere with native Pinaceous conifers, as well as wherever they have been introduced.


Almost all associate with conifers of the family Pinaceae.1
In North America, generally fruit abundantly in late summer and fall.5

Look Alikes:

Eaten by some; others dislike the texture. Many authorities recommend removing the top outer skin of the cap; this part is believed to cause indigestion. Some recommend removing the pore layer.


1 Index Fungorum Record #18623

2 Klofac, W. 2013. A world-wide key to the genus Suillus, Österr. Z. Pilzkd 22:211-278

3 MycoBank #18623

4 Nhu H. Nguyen, Else C. Vellinga, Thomas D. Bruns & Peter G. Kennedy (2016). Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa, Mycologia 108:6, 1216-1228 (also available via

5 Smith, A.H. and Thiers, H.D. (1964) A contribution toward a monograph of North American species of Suillus (pdf). (Image also available at

6 Gibson, Matchmaker: Mushrooms of the Pacific Northwest, Version 2.2.1 (2015) (application, latest version downloadable at

7 Suillus in Danny Miller, Pictorial Key to Mushrooms of the Pacific Northwest (version 2.2.155) (2017)


Common English name: Slippery Jack(s)

Description author: Christian (Request Authorship Credit)
Description editors: IntoTheFlames, Jay , Joseph D. Cohen