Summer bolete

Description

The summer cep is a large mushroom with a cap up to 25 cm across, dark brown, rusty to chocolate, velvety, cracked in older specimens in dry weather. Under the cap it has tubes, at first white, then yellow-green to olive, which do not change colour when pressed. The stem is swollen or club-shaped, light brown, entirely covered with a raised pale net. The flesh is white and does not change colour.

It grows from May to October, even to November, under oaks, beeches, hornbeams and lindens in broadleaved and mixed forests, also in parks. It is one of the earliest-appearing tube fungi. Its flesh is eaten by larvae more often than in other porcini.

It is distinguished from the porcino by a darker, velvety cap without a white border. It can be confused with the bitter bolete, which has a bitter taste and a net darker than the stem. If you are not sure of the species, do not pick or eat it.

Identification features

Cap

Diameter up to 25 cm (some descriptions give up to 30 cm); in young ones hemispherical, smooth and dark brown, later spread out, cushion-shaped and paler. Cuticle velvety, brown, rusty to chocolate; in drought it finely cracks in older specimens, exposing white flesh and forming a net pattern. Margin without a white border or with a very faint one (unlike the porcini).

Hymenophore (underside of the cap)

Tubes up to 35-40 mm, white to greyish-white in young ones, yellow-green to olive-green in older ones; notched around the stem. Pores small, the colour of the tubes, do not change colour when pressed.

Stem

Thickness 2-7 cm, height 8-25 cm (some descriptions give up to about 12 cm), light brown or grey-brown; barrel-shaped and bulging in young ones, later club-shaped, sometimes cylindrical. Covered entirely with a raised net, white in young ones, brownish in old ones, always paler than the stem. Mycelium at the base white. No ring.

Flesh

White to cream, brownish under the cuticle, sometimes slightly yellowish above the tubes; does not change colour in the air. Firm when young, spongy in older ones (according to some descriptions less firm than in other boletes). Taste mild, nutty, smell pleasant. Often attacked by insect larvae.

Spore print and spores

Spore print olive to olive-brown. Spores smooth, ellipsoid-spindle-shaped, sometimes cylindrical, without a germ pore, 13-20 × 4-6 µm, most often 14-16 × 4.5-5.5 µm.

Habitat and distribution

Ecology. A terrestrial mycorrhizal fungus (ectomycorrhiza), less fussy about its host than other porcini. Mainly with oaks, beeches, hornbeams and lindens; at higher altitudes also under spruces, firs and pines; in southern Europe also under sweet chestnut. In the mountains up to over 2000 m a.s.l. under dwarf willows and rock-roses. Grows in broadleaved and mixed forests, less often coniferous, and also in parks and by ponds.

Distribution. North America, Europe and Asia (according to some descriptions mainly Europe), also reported from southern Africa (probably introduced). One of the earliest-appearing tube fungi. Not legally protected in Poland; it is not on the Ministry of Health list of mushrooms allowed on the market.

Fruiting. Usually from May to early October, even to mid-November, usually after warm and damp weather.

What can it be confused with?

• Tylopilus felleus (bitter bolete) — Grows mainly in coniferous forests, has a very bitter taste, and the net on the stem is always darker than the stem. Inedible because of its bitterness; it must not be tasted raw when you are not sure.
• Boletus edulis (porcino) — Cap paler, with a white margin border; less velvety.
• Boletus aereus (bronze bolete) — Very similar, darker.
• Boletus pinophilus — Belongs to the same section; detailed differences - no data.
• Butyriboletus regius (royal bolete) — Caution: similar protected species (strict protection in Poland), not included in the Atlas. Cap pink to rose-red, tubes and pores bright yellow, stem yellow with a fine yellow net, flesh yellow. Do not pick.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The name aestivalis comes from Latin aestas, meaning "summer"; in English it is "summer cep" or "summer bolete".
• It is one of the earliest-appearing tube fungi, fruiting as early as May.
• Genetic analyses indicate that the B. aereus lineage and the B. reticulatus lineage separated about 6-7 million years ago; it is most closely related to lineages from China and Korea identified as B. edulis.
• In 1793 Jean-Jacques Paulet described it as "Le grand Mousseux" and noted that it can be found in summer in the Bois de Boulogne.