Wood hedgehog

Description

The wood hedgehog is a mushroom with a cap 4–10 cm across, whitish to pale orange, often irregular and depressed, dry and smooth. Instead of gills or tubes it has dense, brittle spines underneath, which sometimes run slightly down the stem. The flesh is white and brittle, and turns yellow when damaged.

It grows from July to October in coniferous, deciduous and mixed forests, usually under spruce and beech, often in large groups, on clay soils rich in calcium. It is common in Poland.

No poisonous look-alikes have been described; the similar Hydnum rufescens is smaller and has a more intense colour. Young fruiting bodies may resemble the sheep polypore, but the spines are visible even in very young hedgehog mushrooms. Older fruiting bodies can be bitter.

Identification features

Cap

Diameter 4–10 (15) cm (descriptions also give up to 17, rarely 25 cm), usually depressed in the centre, colour from whitish through cream to pale orange, yellow or tawny. Surface dry, bare and smooth, sometimes finely felted, and may crack in older specimens. Shape variable, margin wavy, inrolled in young ones, irregular; fruiting bodies often fused in groups of several. Very brittle; fades in dry weather.

Hymenophore (underside of the cap)

Spines (not gills or tubes) 2–7 mm long, dense, slender, whitish to pale orange, sometimes running slightly down the stem; in young specimens short and pale yellow, brittle like the cap. With age or after damage they turn yellow-orange-brown.

Stem

Height up to 7 cm (descriptions also give 3–10 cm), thickness 1.5–4 cm (descriptions also give 1–3 cm), usually off-centre, hard, solid, often irregularly bent. Colour from white through cream to rusty brownish, or like the cap. No ring or volva.

Flesh

Thick, white, firm, brittle; turns yellow to orange-brown when damaged. Smell pleasant, fruity; taste pleasant or spicy, bitter in older fruiting bodies. Tasting unknown mushrooms is not recommended.

Spore print and spores

Spore print white to pale cream. Spores colourless, smooth, thin-walled, almost round to broadly ovoid, non-amyloid, usually with one large oil droplet. Size 5.5–9 × 4.5–7 µm (descriptions give different ranges).

Habitat and distribution

Ecology. Mycorrhizal fungus; in Poland most often with spruce and beech, prefers clay soils rich in calcium. Grows singly, in groups or in fairy rings, in coniferous, deciduous and mixed forests, often in large groups. The fruiting bodies are eaten by squirrels.

Distribution. Europe and North America (in both the west and the east); widespread, common in Poland. Listed as vulnerable on the red lists of the Netherlands, Belgium and Germany. Not legally protected in Poland; included in the list of mushrooms approved for sale (Ministry of Health, item 14).

Fruiting. From July to October (November).

What can it be confused with?

• Hydnum rufescens (Polish: kolczak rudawy) — Smaller, more intense colour (apricot to orange), a distinct boundary between the spines and the stem, spines do not run down the stem.
• Sheep polypore (Albatrellus ovinus), especially young fruiting bodies — In hedgehog mushrooms the spines are visible even in fruiting bodies only a few millimetres across.
• Hydnum ellipsosporum — Smaller fruiting bodies (cap 3–5 cm), elliptical spores, 9–11 × 6–7.5 µm.
• Hydnum albidum, Hydnum albomagnum, Hydnum umbilicatum — North American species; detailed differences — no data (e.g. H. umbilicatum is smaller, with a navel-shaped cap).

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 repandum means “bent backwards” and refers to the wavy margin of the cap.
• Genetic studies from 2009 and 2016 showed that the broadly defined species is in fact several cryptic species, including at least four worldwide.
• After the Chernobyl accident, high accumulation of the caesium isotope was found in the fruiting bodies.