Suillus granulatus

What You Should Know

Suillus granulatus is an edible mushroom found in Europe and other parts of the world. It is commonly associated with 2-needled pines like Scots pine and can be recognized by its sticky, orangish brown cap and non-bruising yellow pore surface that may exude a milky liquid when the mushroom is young. It grows with pine trees on both calcareous and acidic soils and can occur in large numbers.

This mushroom can cause stomach upsets in some people. Before cooking, the gelatinous outer layer should be removed, as well as the tubes inside. The fruit bodies of the mushroom are low in fat, high in fiber and carbohydrates, and contain nutraceutical compounds, so they can be considered a functional food.

Additionally, Suillus granulatus is rich in vitamins B and D, as well as minerals such as potassium and phosphorus. Some research suggests that it may have potential health benefits, such as anti-inflammatory and antioxidant properties. However, more research is needed to fully understand the health benefits and potential risks of consuming this mushroom.

Other names: Slippery Jacks, Weeping Bolete, Butterball, Dotted Stalk Suillus, Granulated Bolete, German (Körnchenröhrling), Netherlands (Melkboleet).

Suillus granulatus Mushroom Identification

1. Cap

   The cap is up to 2.76 inches (7 cm) wide, broadly convex, sticky, orangish brown with darker, reddish brown areas, bald, and very finely rugged in a few places.

2. Pore Surface

   The pore surface is dull yellow, with small, slightly angular pores of about 2 per mm, and tubes that are up to 5 mm deep.

3. Stem

   The stem is up to 1.97 inches (5 cm) long, and up to 0.59 inches (1.5 cm) thick, more or less equal, whitish to yellowish, and has inconspicuous glandular dots that blend in with the surface.

4. Flesh

   The flesh is pale yellow in the cap and upper stem, and darker yellow in the stem base, and does not change when sliced.

5. Spore Print

   Ochre or sienna-brown.

6. Habitat

   Forms a symbiotic relationship with 2-needled pines, including Scots pine. It can be found growing alone or in groups in wooded areas or near urban areas with pines, during the summer through fall. It is widespread in Europe and Asia, and possibly present in North America due to the introduction with red pine and other 2-needled pines.

7. Odor and Taste

   Not distinctive.

8. Microscopic Features

   Spores 8–10 x 2.5–3.5 µm; boletoid-fusiform to elongated-ellipsoid; smooth; hyaline to brown in KOH. Basidia about 35 x 7 µm; clavate; 4-sterigmate. Cystidia in bundles; 50–70 x 7.5–10; subfusiform to subclavate-flexuous; thin-walled; smooth; brown in KOH. Pileipellis an ixocutis. Clamp connections not found.

Suillus granulatus Look-Alikes

1. Suillus grevillei

   Has a similar cap, but there is a very distinct ring zone on its stem and its pores are much larger and angular.

2. Suillus luteus

   Another common and widely distributed species occurring in the same habitat. S. luteus has conspicuous a partial veil and ring, and lacks the milky droplets on the pores.

3. Suillus brevipes

   Has a short stipe to the cap, and which does not ooze droplets from the pore surface.

4. Suillus collinitus

   Has the cap of a darker brown color and has, on the cuticle of the cap, some dark radial fibrillae and pink basal mycelium.

5. Suillus bellinii

   Has a paler, almost whitish, cuticle, especially in the young specimens, and the tubules slightly decurrent on the stem.

6. Suillus mediterraneensis

   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 and 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.)

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.

Suillus granulatus Synonyms and Varietes

• Agaricus granulatus(Linnaeus) Lamarck (1783), Encyclopédie méthodique, Botanique, 1, p. 51

• Boletus circinans Persoon (1794), in Römer, Neues magazin für die botanik, 1, p. 107 ('circinnans')

• Boletus circinans var. ß lactifluus (Withering) Persoon (1801), Synopsis methodica fungorum, p. 506

• Boletus collinitus Peck (1872) [1869], Annual report of the state Cabinet of natural history, 23, p. 129

• Boletus granulatus Linnaeus (1753), Species plantarum exhibentes plantas rite cognitas ad genera relatas, 2, p. 1177 (basionyme) Sanctionnement : Fries (1821)

• Boletus granulatus var. lactifluus (Withering) J. Blum (1966) [1965], Bulletin de la Société mycologique de France, 81(4), p. 484

• Boletus inquinans Schrader (1794), Spicilegium florae germanicae, 1, p. 144

• Boletus lactifluus Sowerby (1809)

• Boletus lactifluus Withering (1792), A botanical arrangement of British plants, Edn 2, 3, p. 415

• Boletus miramar Rolland (1904), Bulletin de la Société mycologique de France, 20(4), p. 205

• Boletus schoberi Oudemans (1885), Nederlandsch kruidkundig archief, serie 2, 4(3), p. 220

• Gyrodon miramar (Rolland) Saccardo & Trotter (1912), Sylloge fungorum omnium hucusque cognitorum, 21, p. 254

• Ixocomus granulatus (Linnaeus) Quélet (1888), Flore mycologique de la France et des pays limitrophes, p. 412

• Leccinum lactifluum(Withering) Gray (1821), A natural arrangement of British plants, 1, p. 647

• Rostkovites granulatus (Linnaeus) P. Karsten (1881), Revue mycologique (Toulouse), 3(9), p. 16

• Suillus circinans (Persoon) Poiret (1806), in Lamarck, Encyclopédie méthodique, Botanique, 7, p. 497

• Suillus lactifluus (Withering) A.H. Smith & Thiers (1968), The Michigan botanist, 7, p. 16

• Suillus schoberi(Oudemans) Kuntze (1898), Revisio generum plantarum, 3, p. 536

• Tubiporus flavosulphureus Paulet (1808) [1793], Traité des champignons, 2, p. 389, tab. 182, fig. 1-2

• Viscipellis granulata (Linnaeus) Quélet (1886), Enchiridion fungorum in Europa media et praesertim in Gallia vigentium, p. 156

Sources:

Photo 1 - Author: Holger Krisp (Creative Commons Attribution 3.0 Unported)

Photo 2 - Author: H. Krisp (Creative Commons Attribution 3.0 Unported)

Photo 3 - Author: Kukereu Permaculture (Public Domain)

Photo 4 - Author: David Whyte (Creative Commons Attribution-Share Alike 4.0 International)