Chestnut Bolete

Description

The chestnut bolete is a small pored mushroom with a rusty or chestnut-brown cap (3–10 cm), suede-like in young specimens and cracked into small fields in dry weather. Underneath it has small, white tubes and pores, which turn yellow with age but do not turn blue when cut. The stem is red-brown, and in section it usually has hollow chambers inside.

It grows from July to October, usually singly or in small groups, under oaks in deciduous forests on sandy, acidic soils. In Poland it is rare and is on the Red List of fungi (status R), so it is best collected sparingly, leaving smaller specimens.

In older literature it was assessed more cautiously, and the similar species G. ammophilus is regarded as poisonous. Collect only specimens you recognise with complete certainty.

Identification features

Cap

Diameter 3–10 cm. Young ones convex, mature ones flat or cushion-shaped. Colour light to rusty brown, chestnut-brown, darker with age. Cuticle at first suede-like, later bare; in dry weather it cracks into small fields.

Hymenophore (underside of the cap)

Tubes white when young, then yellowish, do not turn blue when cut; free from the stem (not fused). Pores small, round, white, then yellow; darken slightly when pressed.

Stem

Irregularly cylindrical, variously bent, of a colour similar to the cap (red-brown), sometimes paler at the top. Surface bare, dry, may crack. Inside at first solid, then spongy, finally hollow or with several chambers of different sizes. No ring and no network.

Flesh

White, does not change colour when cut; firm and hard when young, brittle in older specimens. Taste insignificant, smell indistinct.

Spore print and spores

Spore print pale yellow (straw-coloured). Spores ovoid, smooth, almost colourless; size 7–10 × 4–6 µm.

Habitat and distribution

Ecology. Mycorrhizal fungus (ectomycorrhiza), mainly with oaks (Quercus); in New Zealand with Leptospermum. Prefers sandy and acidic soils, avoids calcareous ones.

Distribution. Rare in Poland; on the Red List of Plants and Fungi of Poland (2006) it has the status R (rare, potentially threatened because of a limited geographic range and small habitat areas). Not under species protection in Poland. Occurs in Europe (also in Great Britain), eastern North America, Asia (Taiwan) and New Zealand; it is on the red lists of, among others, Austria, the Czech Republic, Germany, Denmark, Norway, the Netherlands, Sweden and Finland. Grows singly or in small groups in deciduous forests.

Fruiting. From July to October.

What can it be confused with?

• Gyroporus ammophilus — An almost identical species regarded as poisonous, sometimes treated as a variety of G. castaneus; in the catalogue it appears as a synonym of G. castaneus. Detailed differences — no data.
• Gyroporus cyanescens (bluing bolete) — Pale, straw-yellow cap and intense bluing when damaged; the chestnut bolete has a brown cap and does not turn blue.
• Boletes (Boletus, Xerocomus and others) — According to some descriptions it cannot be confused with any other bolete; in true boletes the spore print is olive-brown and the tubes are fused with the stem.

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 genus name Gyroporus means “with round pores”, and the epithet castaneus refers to the chestnut colour of the cap.
• Despite a structure similar to boletes, it has a pale, straw-yellow spore print, which is why it is placed in a separate family, Gyroporaceae.
• It is on the red lists of many countries, including Norway, Montenegro and Russia (including the Moscow region).
• The Polish name was given by Alina Skirgiełło in 1960.