How to identify Summer Bolete

To correctly identify Summer Bolete (Boletus aestivalis), 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.

   The cap measures 6-20 cm (2.4-7.9 in) in diameter, occasionally larger. It is initially hemispherical, expanding to convex and then plano-convex in maturity. The color ranges from various shades of brown: pale coffee brown, yellowish-brown, ochre, or hazel-brown, often paler at the margin. A key distinguishing feature is its velvety surface, which frequently cracks into an intricate network, especially in dry weather, revealing paler flesh beneath. These cracks are particularly prominent in mature specimens. The cap cuticle is dry and not viscid, even when wet.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   Spore-bearing surface consists of tubes and pores. The tubes are initially whitish, becoming yellow-green to olive-green with age. The pores are small, circular, and concolorous with the tubes, not bruising blue when touched. This is a crucial differentiating feature from many blue-staining boletes.

3. 3

   Stem

   Length, shape, surface, and any ring.

   The stem is robust, typically 5-15 cm (2-6 in) long and 2-6 cm (0.8-2.4 in) thick. It is usually bulbous or club-shaped when young, becoming more cylindrical or slightly clavate with age. The color is often paler than the cap, whitish or brownish. The entire surface is covered by a fine, whitish to pale brown reticulation (net-like pattern) that extends from the apex almost to the base, a very important diagnostic character.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   The flesh is thick, firm, and white, remaining white or very subtly discoloring upon cutting, but not bruising blue. It has a mild, nutty, mushroomy taste and a pleasant, often intense, fungal odor.

5. 5

   Fruiting body

   Overall growth pattern.

   The fruit body of Boletus aestivalis is robust and fleshy, typical of a 'cep' type mushroom.

6. 6

   Habitat

   Where it grows and on what substrate.

   This mushroom is mycorrhizal, forming symbiotic relationships with a variety of broadleaf trees, predominantly oak (Quercus spp.), but also beech (Fagus sylvatica), hornbeam (Carpinus betulus), and chestnut (Castanea sativa). It typically grows terrestrially in deciduous and mixed woodlands, preferring well-drained, often calcareous soils.

Key Facts

Cap surfaces

Velvety, often cracked, dry

Growth Form

Solitary or scattered

Spore Print

Olive-brown

Body color

Brownish cap, whitish to brownish stem with pale reticulation, white flesh

Odor

Mild, pleasant, fungal

Flesh bruises

Does not bruise blue or only very subtly discolors

Height

5-15 cm (2-6 in)

Cap Diameter

6-20 cm (2.4-7.9 in)

Fruit body characteristics

• Gill attachment: Adnexed (referring to tubes, not gills)
• Stem shape: Bulbous to club-shaped when young, becoming cylindrical or clavate
• Stem surface: Covered with a prominent white to pale brown reticulation (net-like pattern)
• Ring: Absent
• Stem cross-section: Solid

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