Greville's Bolete

Description

Greville's bolete is a mushroom with a bright, golden-yellow to orange cap, usually 5–10 cm across (up to 15 cm), covered with slippery slime that looks varnished after rain. The pores under the cap are yellow, and the stem has a ring, lemon-yellow above it and orange-brown below.

It grows exclusively under larches, especially in the mountains, but is common throughout Poland. The fruiting bodies appear from summer to autumn.

The presence of a ring on the stem and the association with larch help to distinguish it from the granulated bolete, which grows under pines and has no ring. If you are not sure of the species, do not pick it for eating.

Identification features

Cap

Diameter 4–15 cm (descriptions give different ranges); young ones conical or hemispherical, then bell-shaped, finally flattened and cushion-shaped. Cuticle smooth, bare, covered with slime; dries out in drought, very slippery and shiny when wet. Colour from lemon-yellow to golden-orange, paler near the margin; remnants of the veil may be present on the margin. The cuticle separates from the flesh with great difficulty.

Hymenophore (underside of the cap)

Tubes 5–10 mm long, yellow, later olive-yellow, attached, running slightly down the stem. Covered by a yellow-whitish veil in young specimens. Pores at first round, then angular, yellow, brown-yellow with age; when pressed they turn pink-brown, then darken.

Stem

Height 5–14 cm, thickness up to 2.5 cm, cylindrical or club-shaped, solid, with a ring in the upper part. Above the ring lemon-yellow, slimy, often with a network; below the ring orange-brown (according to some descriptions with rusty-brown streaks). In older specimens the ring vanishes, leaving a trace.

Flesh

Yellow, pinkening in places; in the cap soft and juicy, in the stem hard and fibrous; watery in old ones. When cut or crushed it turns dirty pink (according to some descriptions brownish). Taste insignificant (according to some descriptions from mild to slightly astringent or bitterish), smell indistinct (according to some descriptions none or slightly metallic).

Spore print and spores

Spore print olive-ochre to light brown. Spores smooth, spindle-shaped to ellipsoidal, pale yellow, 7–11 × 3–4 µm.

Habitat and distribution

Ecology. Mycorrhizal fungus (ectomycorrhiza), exclusively with larches; among the three slippery jacks growing under larches it is the most frequently encountered.

Distribution. Europe, North America, North Africa, Australia, also Taiwan. Common in Poland, especially in the mountains. Not legally protected.

Fruiting. July–November.

What can it be confused with?

• Suillus bresadolae var. flavogriseus (Polish: maślak alpejski) — Grows only in the higher parts of the mountains, also under larches; detailed features — no data.
• Suillus flavidus (Polish: maślak błotny) — Listed as similar; detailed differences — no data. Protected in Poland (partial protection), not included in the Atlas — do not pick.
• Suillus granulatus (granulated bolete) — Has no ring on the stem; grows under pines, not under larches.
• Suillus tridentinus — Caution: similar protected species (strict protection in Poland), not included in the Atlas. Cap orange to rusty with darker fibrils, pores orange; under larch, mainly on calcareous soils in the mountains. Do not pick.
• Suillus sibiricus — Caution: similar protected species (partial protection in Poland), not included in the Atlas. Cap yellow with brownish spots, stem with brown dots; grows only under Swiss stone pine (in Poland in the Tatra Mountains). 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

• It grows exclusively under larches, which helps in identification.
• The species epithet commemorates the Scottish botanist Robert Kaye Greville.
• The species contains at least 11 pigments derived from pulvinic acids, responsible for the yellow-orange colour.
• Formerly it was also called maślak strojny and maślak modrzewiowy; Alina Skirgiełło gave the current Polish name in 1960.