How to identify Bitter Beech Bolete

To correctly identify Bitter Beech Bolete (Caloboletus calopus), check each of these features in order. Misidentification is the most common cause of mushroom poisoning, so cross-reference multiple sources.

Step-by-step identification

1. 1

   Cap

   Shape, color, surface texture, and diameter.

   5-15 cm (2-6 inches) in diameter, hemispherical to convex, becoming broadly convex to flat with age. The color is typically pale, whitish-gray, grayish-tan, or buff, sometimes with olive or yellowish tints. The surface is dry, finely tomentose (velvety) when young, becoming smooth with age. It does not crack significantly.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   Pore surface is bright lemon-yellow when young, becoming olive-yellow with age. Pores are small and round. They instantly bruise blue when touched or damaged. Tubes are adnate to depressed around the stem.

3. 3

   Stem

   Length, shape, surface, and any ring.

   5-15 cm (2-6 inches) long and 2-5 cm (0.8-2 inches) thick, stout and club-shaped when young, becoming more cylindrical or bulbous at the base with age. The upper part of the stem is yellow, often with a fine red reticulum (net-like pattern) that extends downwards. The lower part of the stem is typically flushed with red or carmine, sometimes entirely red. The base can be yellowish. The surface is dry.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   Pale yellow, firm, and thick. It stains blue when cut or bruised, especially in the cap and upper stem. The taste is intensely bitter, even a small piece can ruin a meal.

5. 5

   Fruiting body

   Overall growth pattern.

   A robust, fleshy mushroom with a cap, pores, and a stout stem.

6. 6

   Habitat

   Where it grows and on what substrate.

   Mycorrhizal, forming symbiotic relationships primarily with broadleaf trees, especially beech (Fagus) and oak (Quercus), but can also be found with conifers like spruce (Picea) and fir (Abies). Grows solitarily or scattered on the ground in deciduous and mixed forests.

Key Facts

Cap surfaces

Dry, finely tomentose to smooth.

Growth Form

Solitary to scattered.

Spore Print

Olive-brown.

Body color

Cap: whitish-gray, grayish-tan; Pores: lemon-yellow to olive-yellow; Stem: yellow with red flush and reticulum.

Odor

Mild.

Flesh bruises

Blue, especially in the cap and upper stem.

Height

5-15 cm (2-6 inches)

Cap Diameter

5-15 cm (2-6 inches)

Fruit body characteristics

• Gill attachment: Adnate to depressed (tubes)
• Stem shape: Club-shaped to cylindrical, often bulbous at base.
• Stem surface: Dry, yellow with red reticulum in upper part, red-flushed below.
• Ring: Absent
• Stem cross-section: Solid

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