Rooting Bolete

Description

The rooting bolete is a large, pale bolete: the cap, usually 8–15 cm in diameter (sometimes much larger), is dirty white, whitish-grey or grey-beige, suede-like and often cracks. The pores are lemon-yellow and turn strongly blue when touched, as does the flesh when cut. The stem is yellow, with a delicate net only in the upper part, and it narrows towards the bottom and often roots in the substrate.

It grows from July to October in warm, sunny deciduous and mixed forests, under beeches, oaks, limes and hazel, preferably on calcareous soil. In Poland it is rare and under strict species protection, so collecting it is prohibited.

It is sometimes confused with porcini, but its flesh quickly turns blue and is very bitter. It is inedible, and after eating it severe vomiting and diarrhoea, also bloody, have been recorded. Do not pick it and do not destroy it.

Identification features

Cap

Diameter 8–15 cm, up to 30 cm (descriptions give 7.5–30 cm). Hemispherical when young, then somewhat flattened. Pale colour: dirty white, whitish-grey, cream or grey-beige. Cuticle suede-like, downy at first, often cracking in the middle.

Hymenophore (underside of the cap)

Tubes long (15–30 mm), notched; pale yellow when young, then lemon-yellow, olive-yellow with age. Pores small, round, lemon-yellow; they turn strongly blue when touched or damaged.

Stem

Height 5–13 cm (descriptions give different ranges), thickness 3–4 cm; barrel-shaped when young, then spindle-shaped, thickened in the middle, narrowed and pointed at the bottom, usually rooting in the substrate. Buff-yellow, lemon-yellow, intensely lemon in the upper part, paler towards the bottom; turns blue where damaged. Reticulation delicate, pale straw-coloured, visible only in the upper part (rarely indistinct). No red colour.

Flesh

Firm, pale yellow, lighter in the cap, cream to straw-coloured; turns blue immediately and distinctly when cut. Smell unpleasant, mild at first, later bitterish. Taste intensely bitter — do not taste it.

Spore print and spores

Spore print olive-brown (descriptions also give olive-nut). Spores smooth, ellipsoid to spindle-shaped; size 11.5–14 × 4–5.5 µm (given only in some descriptions).

Habitat and distribution

Ecology. A mycorrhizal fungus (ectomycorrhiza) with many species of deciduous trees: beech, oak, hornbeam, sweet chestnut, lime, hazel. Grows in deciduous and mixed forests in warm and sunny places; preferably on calcareous soil, but according to some descriptions also on acidic soil.

Distribution. Most numerous in Europe, mainly in the southern part; isolated localities in China, North America and Africa. Rare in Poland (by 2020, 4 historical and 31 recent localities). The species is under strict species protection in Poland (Journal of Laws 2014, item 1408); 2006 Red List: V (vulnerable), also on the red list in Norway. Common in southern England.

Fruiting. From July to October (in warm periods of summer and early autumn).

What can it be confused with?

• Boletus edulis (porcino) — The flesh of the porcino does not turn blue when cut and is not bitter; no yellow pores turning blue when touched.
• Caloboletus calopus (bitter beech bolete) — Stem partly carmine-red, without a rooting end; flesh turns blue less strongly. Also inedible.

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 epithet radicans refers to the stem that ends in a root.
• In Poland by 2020, 4 historical and 31 recent localities were known.
• Until 2014 it was placed in the genus Boletus; phylogenetic studies showed that it belongs to a separate genus, Caloboletus.
• It is on the red list of threatened species also in Norway.