Suillus granulatus: The Ultimate Mushroom Guide

About The Suillus granulatus Mushroom

Suillus granulatus is a widespread edible ectomycorrhizal fungus in Eurasia and North America.

It is an easily recognizable fungus that provided attention is paid to some peculiar characters: the granulations, rather thick, present on the stem, the pores secreting opalescent droplets in the young fungi, the surface of the cap without fibrillae and the white basal mycelium. The caps of most species are slimy or slippery, especially after rain.

This mushroom has a nutty taste which makes it a more favorable species for collecting.

Other names: Slippery Jacks, Weeping Bolete, Butterball, Dotted Stalk Suillus.

Suillus granulatus Identification

1. Ecology

   Mycorrhizal with various pines; often appearing in plantations of eastern white pine; growing alone or gregariously; summer and fall--often among the first species of Suillus to appear; widely distributed. In my area (central Illinois) it has quite a long fruiting period, beginning in August or September and lasting through November.

2. Cap

   5-15 cm; convex becoming broadly convex; sticky or slimy; smooth; variable in color but typically buff, yellowish, or pale cinnamon at first, becoming darker cinnamon brown or orangish brown; often with the color breaking up in maturity to form a patchwork pattern; without partial veil remnants.

3. Pore Surface

   Whitish at first; soon yellowish; often with droplets of cloudy liquid when young; not bruising, or bruising and spotting cinnamon to brownish; pores about 1 mm wide at maturity; not strongly boletinoid but sometimes weakly so in age; tubes about 1 cm deep.

4. Stem

   4-8 cm long; 1-2 cm thick; equal or with a tapering base; with tiny, tan or brownish glandular dots on the upper half; without a ring; white, developing bright yellow shades near the apex or overall.

5. Flesh

   White at first, but soon pale yellow; not staining on exposure.

6. Spore Print: Cinnamon brown to brown.

Suillus granulatus Look-Alikes

It may be mistaken with: Suillus collinitus (Fries) Kuntze, which, however, has the cap of a darker brown color and has, on the cuticle of the cap, some dark radial fibrillae and pink basal mycelium; Suillus bellinii (Inzenga) Watling, which, however, has a paler, almost whitish, cuticle, especially in the young specimens, and the tubules slightly decurrent on the stem; Suillus mediterraneensis (Jacquetant & Blum) Redeuilh, which however has the cuticle with thin innate fibrillae and the color which, when ripe, is olive-brown ochraceous, the flesh more markedly yellowish and with a prevalent habitat under the Pinus halepensis.

Suillus granulatus Taxonomy & Etymology

When, in 1763, Carl Linnaeus first described this mushroom he named it Boletus granulatus. It was the French physician and naturalist Henri François Anne de Roussel (1748 - 1812) who, in 1796, transferred this mushroom to the Suillus genus. (Suillus is an ancient term for a fungus, and it comes from the same origin as 'swine' - a reference to the greasy nature of pigs and of this group of boletes, perhaps.)

Suillus granulatus has several synonyms including Boletus lactifluus Sowerby, Leccinum lactifluum (Sowerby) Gray, Ixocomus granulatus (L.) Quél., and Suillus lactifluus (Sowerby) A.H. Sm. & Thiers. Among its many common names are Granulated Bolete, Ringless Slippery Jack (an ambiguous term that has also been applied to other Suillus species) and, again ambiguously, Dotted-stem Bolete.

The generic name Suillus means of pigs (swine) and is a reference to the greasy nature of the caps of fungi in this genus. The specific epithet granulatus means, as it suggests, granulated. This is a reference to the granular surface of the upper part of the stems of these boletes.