Mottled bolete or Bitter bolete

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.

Cap 5–10 cm, hemispherical in young mushrooms, then cushion-shaped. The surface is dry at first and slightly sticky in damp weather. The color is distinctive — a mouse-gray or dark brown background with scattered elongated light gray, yellowish or cream spots that resemble natural camouflage. The cap skin does not peel off.

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.

The hymenophore is tubular, free, with a notch near the stem. White when young, then beige, light brown in mature mushrooms. The pores are small. They darken slightly when pressed.

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.

Stem 12–18 cm tall, 2–2.5 cm thick, cylindrical or slightly tapering upward. White, with characteristic dark gray or brown fibrous scales — a typical feature of the genus Leccinum. In young mushrooms the scales are lighter, in old ones darker.

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.

The flesh is white, firm at first, soft and spongy with age. When cut: it turns pink in the cap, slightly blue in the tubes, and in the stem partly pink, partly green or bluish at the base. This multicolored reaction gave the species its name, “variicolor” (many-colored).

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.

Smell faint, pleasantly mushroomy. Taste mild, not bitter.