Boletus aereus: The Ultimate Mushroom Guide

About The Boletus aereus Mushroom

Boletus aereus is a most sought-after edible mushroom. It is just as good as its famous close relative, Boletus edulis but its flesh is rather firmer.

Commonly found at the edges, beside walks or in clearings in oak and beech woodlands, Boletus Fereus tends to fruit a little later than Boletus reticulatus.

The fungus produces spore-bearing fruit bodies above ground in summer and autumn. Like other boletes, B. aereus has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores.

Other names: Queen Bolete, Bronze Bolete.

Boletus aereus Identification

1. Cap

   Medium and big size, from 5-10 (30) cm, fleshy, initially hemispheric then convex, finally flat, slightly overhanging margin, dry cuticle, finely velvety in the young specimen, without decorations, shows a bistre-brown coloring to assume a blackish “bronzy” tone, but also paler colorings can be found.

2. Hymenophore

   Very small tubules, long, adnate, thick, from white to yellow to olive-green with the ripening of the spores, easily loosening from the flesh of the cap, non-staining at the cut; small pores concolorous to the tubules, non-staining when touched.

3. Stem

   5-18 (20) x 5-12 cm, firm and sturdy, from obese to barrel-shaped, rounded, bulbous, of brown color, always paler than the cap, shows a concolorous to the cap small net, which extends mostly on the upper part.

4. Flesh

   White, firm, compact, and non-staining. Fungous smell and taste.

5. Chemical reactions

   The flesh, when in contact with strong bases such as the KOH (potassium hydroxide) and NaOH (sodium hydroxide), assumes a more or less brown coloring.

6. Spores

   Spindle-shaped, smooth, 13-16 x 4-5 µm.

7. Habitat

   In woods, especially oaks, but also chestnut, purely xerophytic species, loving the warm and dry locations, much more infrequent in the north whilst it is more common in the Mediterranean and Apennine zones. The growth takes place in autumn.

8. Edibility

   Excellent; even raw, if consumed in small quantities.

Boletus aereus Similar Species

1. Boletus reticulatus

   Is very similar to B. aereus, also occurring during the summer months under broad-leaved trees. It has a paler, often cracked cap and a usually paler stipe covered in a more elaborate and pronounced whitish reticulation, often extending to the stipe base.

2. Boletus pinophilus

   Occurs under conifers, mostly Pinus sylvestris, and has a reddish-brown cap. Microscopically, it can be separated by the more inflated, club- to spindle-shaped hyphal ends of the pileipellis.

3. Boletus edulis

   Occurs later in the season during lower temperatures, mostly under Picea. It has a paler viscid cap and a paler stipe with an acute white reticulation. Microscopically, it has gelatinized hyphal ends in the pileipellis.

Boletus aereus Nutrition Facts

Based on analyses of fruit bodies collected in Portugal, there are 367 kilocalories per 100 grams of bolete (as dry weight).

The macronutrient composition of 100 grams of dried bolete includes 17.9 grams of protein, 72.8 grams of carbohydrates, and 0.4 grams of fat.

By weight, fresh fruit bodies are about 92% water. The predominant sugar is trehalose (4.7 grams/100 grams dry weight; all following values assume this mass), with lesser amounts of mannitol (1.3 grams).

There are 6 grams of tocopherols, the majority of which is gamma-tocopherol (vitamin E), and 3.7 grams of ascorbic acid.

Boletus aereus Taxonomy & Etymology

The scientific name Boletus aerus originated in Jean Baptiste Francois Pierre Bulliard's 1789 description of this species. Synonyms of Boletus aereus include Boletus mamorensis Redeuilh

The generic name Boletus comes ​​from the Greek bolos, meaning lump of clay; the origin of the specific epithet aereus is Latin and means copper or bronze (in color) - hence the common name Bronze Bolete. Some people refer to it as the Black Porcini or the Black Cap Bolete.