Summer bolete or Bitter bolete

Cap 8–25 cm (sometimes up to 30), hemispherical in young mushrooms, then cushion-shaped, almost flat in old ones. Color warm bronze-brown, light brown, darker in the center. The surface is matte, slightly tacky in wet weather. A characteristic feature: in mature mushrooms the cap becomes covered with a fine network of cracks — a “crackled” look, like fired clay.

The cap of the bitter bolete reaches 4 to 15 centimeters across, and in especially good years you'll find real giants up to 20 centimeters. When young it is neatly hemispherical, opening with maturity to convex and later almost flat and spread out. The cap surface is dry, delicately velvety or finely felty to the touch in young mushrooms, but becomes smooth with age. The color palette ranges from light hazel and coffee brown to a warm ochre-brown, which especially heightens the deceptive resemblance to porcini.

Tubes free or notched at the stem. White when young, then yellowish, olive-green in mature mushrooms. Pores small and round. Does NOT turn blue when pressed — a key feature.

Under the cap lies a tubular hymenophore, which is the main giveaway of this impostor. In very young mushrooms the tubes and pores are whitish, which, once again, recalls porcini, but very quickly they take on a characteristic dirty pink or flesh-pink hue. It's this pinkness that firmly sets the bitter bolete apart from true porcini, whose hymenophore can be white, yellow or olive, but never pink. When pressed or damaged, the pores often turn brown, developing rusty brown spots.

Stem 10–25 cm tall, 2–7 cm thick, club-shaped in young mushrooms, cylindrical in adults. Color light brown, cream. The most characteristic feature: the whole stem is covered with a distinct white network — broad, coarse, easy to see (hence the Latin “reticulatus,” meaning “net-like”). This is the main difference from the other porcini.

The stem of the bitter bolete is massive and sturdy, 4 to 10 centimeters tall and up to 3 centimeters thick. It is swollen and club-shaped, especially thickened at the base, which makes the mushroom look stocky and dependable. The stem is colored in ochre-brown tones, lighter at the top and darker toward the base. The most important diagnostic detail is the net pattern: unlike porcini's delicate pale netting, the bitter bolete's net is distinct, coarse and dark, chocolate-colored or even blackish, and clearly visible to the naked eye. There is no ring and no volva at all.

Flesh white, dense, does NOT change color when cut. Fibrous texture, with a pleasant resistance under the knife. It gets maggoty about as often as the classic porcini — and a bit less readily than the bronze bolete.

The flesh of the bitter bolete is thick, dense and fleshy, white or slightly cream-colored. When cut it mostly stays unchanged, although in some specimens it may turn faintly pink on exposure to air. There's none of the bluing typical of many boletes. But the flesh's main feature lies not in its color but in its taste: it is extraordinarily, unbearably bitter, like bile or quinine. It's this bitterness, which cooking doesn't destroy, that makes the mushroom unfit for the table.

Smell rich and mushroomy, with nutty notes, stronger in young mushrooms. Taste mild, slightly sweet, not bitter. Dried, it keeps its aroma well.

The smell of the bitter bolete is faint and fairly nondescript, typically mushroomy, with no sharp or unpleasant notes. Unlike the taste, the aroma carries no warning at all and may well seem pleasant. That's exactly why you shouldn't rely on your nose to identify this species — the deceptively mild smell only adds to its overall resemblance to the noble porcini.