Xerocomus subtomentosus

What You Should Know

Xerocomus subtomentosus is a species of Bolete fungus in the family Boletaceae. This medium to large mushroom has a brown cap, chrome-yellow pores, and a yellowish stem. It occurs throughout Eurasia, North America, and Australia and grows with a wide range of hardwood and conifer trees. It forms symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue.

It is edible, although not highly regarded. Its mild taste makes it suitable for mixed mushroom dishes. Elemental analysis of specimens collected from Notec Forest in western Poland determined the mushrooms to have abundant amounts of potassium, phosphorus, and magnesium, with mean values of 46000, 8400, and 1100 milligram/kilogram dry weight, respectively, in the caps. The levels of the toxic metals cadmium, mercury, and lead in the mushrooms "did not pose a threat to a consumer's health".

Other names: Suede Bolete, Brown And Yellow Bolet, Boring Brown Bolete, Yellow-Cracked Bolete, Fluweelboleet (Netherlands), Hřib Plstnatý (Czech Republic), Ziegenlippe (German).

Xerocomus subtomentosus Mushroom Identification

1. Cap

   3–12 cm; convex, becoming broadly convex; dry; finely velvety; brownish yellow to brown, yellowish-brown, or olive-brown; often becoming cracked in age.

2. Pore Surface

   Yellow, becoming olive-yellow with maturity; often bruising blue, or not bruising; pores xerocomoid, 1–3 per mm; tubes to 10 mm deep.

3. Stem

   4–7.5 cm long; 1–2 cm thick; equal above a tapered base; dry; solid and tough; sometimes ribbed near the apex or over the upper half, but not reticulate; usually featuring tiny reddish granules on a whitish to the yellowish surface; basal mycelium white.

4. Flesh

   White; usually turning pale blue in the cap when sliced.

5. Chemical Reactions

   Ammonia dark red on cap; negative on flesh. KOH red to orangish on cap; orangish on flesh. Iron salts negative to gray on cap; negative to gray on flesh.

6. Spore Print

   Olive to olive-brown.

7. Habitat

   Mycorrhizal with a wide variety of hardwoods (including oaks, beech, birches, aspens); growing alone, scattered, or gregariously; summer and fall, or overwinter in warm climates; originally described from Sweden; widely distributed in Europe and North America; also known from Asia and Oceania.

8. Microscopic Features

   Spores 10–14 x 3.5–5 µm; boletoid-fusiform; smooth; dull yellow in KOH. Hymenial cystidia inconspicuous; 25–40 x 5–10 µm; lageniform or fusiform; smooth; thin-walled; smooth; hyaline. Pileipellis a collapsing trichoderm; golden in KOH; elements 5–12.5 µm wide, smooth; terminal cells cylindric with rounded apices.

Xerocomus subtomentosus Look-Alikes

1. Xerocomellus chrysenteron

   Has a reddish stem and usually untapered.

2. Xerocomus silwoodensis

   The rare European species, described as new to science in 2007, is similar in appearance to X. subtomentosus. It can be distinguished from the latter in the field by the darker reddish-brown tones of the cap and its preference for associating with Populus trees. It has white flesh that becomes yellow-tinged on exposure to air.

3. Xerocomus chrysonemus

   Has bright yellow flesh and mycelium.

4. Xerocomus ferrugineus

   Found under conifers and also has yellow mycelium.

Xerocomus subtomentosus Cultivation

1. The place to grow

   Forest mushrooms grow in forests and groves, so we have to adapt the choice of location to provide them with conditions as similar as possible to their natural environment - forest trees (oak, pine, birch) should be found there. A shady and quiet place is ideal.

2. Substrate preparation

   Buy or prepare the mycelium with 5 liters of peat (moistened peat is ideal), 1 liter of charcoal (Instead of charcoal, you can use ashes from a fireplace or fireplace where only wood was used). To improve the parameters, it is also advisable to use 0.5 l of gypsum and 0.5 l of vermiculite or perlite. Moisten the prepared substrate. The ideal way to check if the substrate is properly moistened is to scoop it up with your hands and press it. A few drops of water should come out.

3. Dosage

   Dig several smaller holes around the tree (preferably so that the roots can be seen), pour in about 0.5 l of the prepared substrate and cover with a 5-centimeter layer of soil. In the places where we poured the substrate, it is advisable to use bark, pine needles, or leaf mulch. Thus, the prepared place does not require any further adjustments, just occasionally sprinkle with a small amount of water. Especially in the period when it rained for 10 to 14 days. Planting can be done from April to late autumn.

4. Mycorrhiza

   Mycorrhiza is a symbiosis of plants with fungi. The fungus draws nutrients from the plants, and the plant gets more coverage thanks to the fungus to obtain water and mineral salts. In addition to physiological and nutritional functions, mycorrhiza protects forest trees from diseases, "nourishes and protects". Mycorrhiza is a very complex process, which is the reason why we do not always manage to achieve success in cultivation. It depends on many factors: mushroom variety, old wood, type of soil, environment, etc. If we prepare the appropriate conditions for development and symbiosis, the first fruiting bodies should appear 2-3 years after inoculation.

Xerocomus subtomentosus Taxonomy and Etymology

Xerocomus subtomentosus was first described in 1753 by the father of taxonomy Carl Linnaeus as Boletus subtomentosus. The starting date of fungal taxonomy had been set as January 1, 1821, to coincide with the date of the works of the 'father of mycology', Swedish naturalist Elias Magnus Fries, which meant that the name required sanction by Fries (indicated in the name by a colon) to be considered valid, as Linnaeus' work preceded this date. It was thus written Boletus subtomentosus L.:Fr. However, a 1987 revision of the International Code of Botanical Nomenclature set the starting date at May 1, 1753, the date of publication of Linnaeus' seminal work, the Species Plantarum. Hence the name no longer requires the ratification of Fries' authority.

French mycologist Lucien Quélet had classified a number of Boletus species in the genus Xerocomus, with Xerocomus subtomentosus made the type species. The genus name is derived from the Ancient Greek Xeros "dry" and kome "hair", and refers to the velvety surface of the cap. This classification was disputed, with many authorities not recognising the genus and continuing to use Boletus subtomentosus; however genetic analysis published in 2013 confirmed the distinctness of this species and its close relatives from the core group of fungi in the genus Boletus (sensu stricto).

Its specific name subtomentosus is Latin "finely haired", referring to its cap. Mushroom author David Arora nicknamed the mushroom the boring brown bolete from its lack of taste and appeal.

Xerocomus subtomentosus Synonyms and Varieties

• Boletus subtomentosus L., 1753 (basionym)

• Boletus crassipes Schaeff., 1774

• Boletus cupreus Schaeff., 1774

• Boletus kuthanii Assyov & Denchev 2004

• Boletus lanatus Rostk., 1844

• Boletus leguei Boud., 1894

• Boletus pannosus Rostk., 1844

• Boletus striipes Fr., 1874

• Boletus subtomentosus f. gracilis Killerm. (1925)

• Boletus subtomentosus f. leguei (Boud.) Vassilkov (1970)

• Boletus subtomentosus f. roseipes Killerm. (1925)

• Boletus subtomentosus L. (1753) f. subtomentosus

• Boletus subtomentosus L. (1753) subsp. subtomentosus

• Boletus subtomentosus L. (1753) var. subtomentosus

• Boletus subtomentosus L. 1753

• Boletus subtomentosus subsp. punctatipes C. Martín (1904)

• Boletus subtomentosus var. albo-ochraceus Pilát (1951)

• Boletus subtomentosus var. bulbosus C. Mart. (1894)

• Boletus subtomentosus var. conoides Pers. (1800)

• Boletus subtomentosus var. crassipes (Schaeff.) Smotl. (1912)

• Boletus subtomentosus var. cupreus (Schaeff.) Pers. (1800)

• Boletus subtomentosus var. gilvus Alb. & Schwein. (1805)

• Boletus subtomentosus var. lanatus (Rostk.) Smotl. (1912)

• Boletus subtomentosus var. lepidopodes Opat. (1836)

• Boletus subtomentosus var. luteolus Velen. (1922)

• Boletus subtomentosus var. marginalis Boud. (1907)

• Boletus subtomentosus var. murinus Pers. (1800)

• Boletus subtomentosus var. nigricans E.A. Herrm. (1922)

• Boletus subtomentosus var. pannosus (Rostk.) Smotl. (1912)

• Boletus subtomentosus var. perplexus A.H. Sm. & Thiers (1971)

• Boletus subtomentosus var. rubiginosus Pers. (1800)

• Boletus subtomentosus var. sanguineus Opat. (1836)

• Boletus subtomentosus var. sistotremoides J. Kickx f. (1867)

• Boletus subtomentosus var. subbadius R. Schulz (1924)

• Boletus subtomentosus var. subbulbosus Pers. (1800)

• Boletus subtomentosus var. tesselatus Opat. (1836)

• Boletus subtomentosus var. tomentosus Opat. (1836)

• Boletus subtomentosus var. virescens Bres.

• Boletus xanthus (E.-J. Gilbert) Merlo 1980

• Ceriomyces subtomentosus (L.) Murrill, 1909

• Leccinum subtomentosum (L.) Gray, 1821

• Rostkovites subtomentosus (L.) P. Karst., 1881

• Suillus lanatus (Rostk.) Kuntze (1898)

• Suillus leguei (Boud.) Kuntze (1898)

• Suillus pannosus (Rostk.) Kuntze (1898)

• Suillus striipes (Fr.) Kuntze (1898)

• Suillus subtomentosus (L.) Kuntze, 1898

• Versipellis subtomentosus (L.) Quél., 1886

• Xerocomopsis subtomentosus (L.) Reichert, 1940

• Xerocomus ferrugineus var. leguei (Boud.) Bon (1994)

• Xerocomus flavus Singer & Kuthan, 1976

• Xerocomus lanatus (Rostk.) Singer 1946

• Xerocomus leguei (Boud.) Montegut ex Bon (1985)

• Xerocomus subtomentosus (L.) Quél. (1888)

• Xerocomus subtomentosus (L.) Quél. (1888) f. subtomentosus

• Xerocomus subtomentosus (L.) Quél. (1888) subsp. subtomentosus

• Xerocomus subtomentosus (L.) Quél. (1888) var. subtomentosus

• Xerocomus subtomentosus f. rubrotinctus Simonini & Contu (2000)

• Xerocomus subtomentosus f. squarrosus A.N. Petrov (1983)

• Xerocomus subtomentosus f. xanthus E.-J. Gilbert, 1931

• Xerocomus subtomentosus subsp. punctatipes (C. Martín) Dennis (1955)

• Xerocomus subtomentosus var. albo-ochraceus (Pilát) Pilát (1974)

• Xerocomus subtomentosus var. leguei (Boud.) Maire (1933)

• Xerocomus subtomentosus var. luteolus (Velen.) Šutara (2008)

• Xerocomus xanthus (E.-J. Gilbert) Curreli (1989)

Sources:

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