Hollow Bolete

Description

The hollow bolete is a rare fungus with a cap 4–12 cm across, dry and felty-scaly, in shades from yellow-brown through red-brown to brown. The underside is made up of very large, radially elongated yellow pores, with short tubes running slightly down the stem. The stem is hollow inside, cylindrical, with a whitish ring in the upper part. The flesh does not change colour when damaged; the taste is slightly sour.

It grows exclusively under larches, more often in the mountains. In Poland it is rare (more than 80 localities) and under partial protection.

Do not collect it: it is protected and rare. If you are not sure of the identification, do not eat it.

Identification features

Cap

Diameter 4–12 cm; at first hemispherical or conical with an inrolled margin, with age flat with a small umbo in the centre, margin sharp. Entirely covered with fine, darker tufts, felty-scaly, dry (also described as fibrous, sometimes with veil remnants on the margin). Colour from yellow-brown through red-brown to brown.

Hymenophore (underside of the cap)

Tubes short, slightly decurrent on the stem. Pores very large, radially elongated, yellow to olive-yellow (also described as buff); they do not change colour. Covered by a whitish veil when young.

Stem

Height 4–10 cm, thickness 1–2 cm; cylindrical, thickened at the base, hollow (hence the name). Colour of the cap or paler; in the upper part with a whitish, sometimes barely visible ring.

Flesh

In the cap yellowish, spongy; in the stem white, drier and firmer. Does not change colour when damaged. Smell pleasant; taste slightly sour, in older specimens astringent or somewhat bitter. Raw flesh should not be tasted.

Spore print and spores

Spore print olive-yellowish. Spores ellipsoid-fusiform; size 7–19 × 3–4 µm.

Habitat and distribution

Ecology. Terrestrial mycorrhizal fungus, associated exclusively with larches (in North America, on the Pacific coast, also with larch).

Distribution. Europe and North America. More than 80 localities are recorded in Poland, more often in the mountains; Red List 2006: R (rare). Protection: partial in 1995–2004, strict from 2004, partial again from 2014 (Dz.U. 2014 item 1408, as Boletinus cavipes).

Fruiting. No data.

What can it be confused with?

• Other suilloid fungi and boletes growing under larch — Detailed differences — no data. Identifying features: hollow stem, very large, radially elongated pores running down the stem, association with larch.

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 cavipes means "hollow foot" in Latin and refers to the hollow stem.
• The protection status has changed: partial protection in 1995–2004, strict from 2004, and partial again from 2014.
• The species has been moved between genera many times (Boletus, Boletinus, Boletopsis, Suillus and others), hence the many Polish names: borowik pustotrzonowy, borowiec dęty, maślak dęty, borowiczak dęty.
• It grows exclusively under larch; in Poland it is more common in the mountains.