Ruby Bolete

Description

The ruby bolete is a small bolete with a cap 3–10 cm across, dry and velvety, intensely carmine red, paler and dull pink with age. In dry weather the cap cracks. The underside consists of yellow pores that slowly turn blue when touched. The stem is slender, yellow, usually with a red flush or spots. The flesh is yellowish and turns blue when cut.

It grows from July to September in deciduous forests and parks, under oaks, lindens and birches. In Poland it is not common, so finding one is an occasion rather than the rule.

It is told apart from similar boletes by the red colour of the cap and the yellow stem with red spots. If you are not sure of the species, do not pick it or eat it. Fruiting bodies attacked by the yellow mould are not fit to eat.

Identification features

Cap

Diameter 3–10 cm (usually no more than about 6 cm); young hemispherical, then expanding to flat. Surface dry, velvety, cracking in dry weather. Colour at first intense carmine to scarlet or raspberry red, red with age, finally dull pink; it darkens and becomes dingy with age. The cap skin cannot be separated from the flesh. The outermost margin often has a pale yellow or white band.

Hymenophore (underside of the cap)

Tubes 6–15 mm long, greenish yellow, notched or slightly decurrent at the stem. Pores at first lemon yellow to pale yellow, olive or greenish with age; when pressed they slowly turn blue. Descriptions give different pore sizes.

Stem

Height 3–12 cm (usually up to about 7.5 cm), slender, cylindrical, often curved, sometimes tapering. Lemon yellow at the apex, pale yellow lower down, usually flushed with red or with red spots. Tends to split lengthwise. No ring.

Flesh

Yellowish to straw-coloured, reddish only just beneath the cap skin. Turns blue slowly when cut, most strongly above the tubes. In the stem pale yellow at the top and yellow lower down; at the base there may be a distinct brick-red or orange patch. Smell pleasant, indistinct; taste indistinct, slightly soapy according to some descriptions. Do not taste the flesh.

Spore print and spores

Spore print olive to olive-brown. Spores smooth, 10–13 × 4–5 µm; golden in KOH.

Habitat and distribution

Ecology. A mycorrhizal fungus of broadleaved trees; oaks, lindens and birches are mentioned in descriptions. Grows on the ground in deciduous forests. Fruiting bodies are sometimes attacked by the parasitic fungus Hypomyces chrysospermus.

Distribution. Europe and eastern North America (probably introduced there with tree seedlings from Europe); in all descriptions regarded as not very common to rare. In Poland not very common. In southern England rare, mainly under oaks. Not legally protected in Poland. Not on the list of fungi approved for sale in Poland.

Fruiting. From July to September; according to some descriptions also in autumn.

What can it be confused with?

• Xerocomus armeniacus (Polish: podgrzybek ormiański) — Often confused with it in Europe because of its similarly dry, velvety cap; however, it has no red colour at the base of the stem.
• Xerocomellus chrysenteron (Polish: suchogrzybek złotopory) — A similar species; detailed features need to be compared.
• Hortiboletus coccyginus — A similar species, mentioned alongside H. rubellus; detailed features need to be compared.
• Baorangia bicolor (Polish: borowik dwubarwny) — Described as almost identical to H. rubellus; it is a North American species.
• Boletus fraternus, Xerocomellus mendocinensis — Mentioned as similar species; detailed features need to be compared.

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

• Until 2015 the species was known as Boletus rubellus, and in Polish literature also as "podgrzybek wielobarwny"; the genus Hortiboletus was separated on the basis of molecular studies.
• The English name is "ruby bolete" (in Polish, "rubinowy borowik").
• The previously widely used name Boletus versicolor (Rostkovius, 1844) became a synonym, because Krombholz's name from 1836 is older.
• In North America the species was probably introduced with tree seedlings from Europe.