Common stinkhorn

Description

The common stinkhorn is a mushroom of unusual structure. The young fruiting body looks like a white-cream egg the size of a hen's egg, partly hidden in the ground. The egg quickly bursts and a white, spongy column, hollow inside and 10–30 cm tall, grows out of it, topped with a conical head covered with an olive-green, slimy mass.

It grows from summer to late autumn in forests, parks, thickets and gardens, often on litter rich in wood. In Poland it is common. It is easiest to recognise by its smell: the mature fruiting body gives off a strong, carrion-like stench that attracts flies, which spread the spores.

The stinkhorn is hard to confuse with other mushrooms, but the young eggs can be confused (e.g. with the eggs of amanitas or with puffballs), so they must not be collected for eating without cutting them open and identifying them with certainty.

Identification features

Cap

Properly the head of the receptacle: conical or thimble-shaped, a few to a dozen or so cm long (descriptions also give 2–4 cm in height), covered with a slimy, olive-green to green-brown spore-bearing mass (gleba). After insects have eaten the mass it reveals a yellowish, pitted-reticulate surface, somewhat similar to the surface of a morel.

Hymenophore (underside of the cap)

No gills or tubes: the spores are formed in the gleba covering the head of the receptacle.

Stem

Receptacle (stem) 10–30 cm high and about 4–5 cm in diameter, cylindrical, narrowing towards the top, porous (spongy), brittle, hollow in the middle, white; at the base a sac-like volva. No ring. The young fruiting body is an egg (the so-called devil's egg): spherical or ovate, 4–6 × 3–5 cm, white, cream or pinkish, with a two-layered covering with a gelatinous layer between them, attached to the substrate by cords of mycelium.

Flesh

In the egg from the outside: a thick white covering (peridium), beneath it an olive gelatinous gleba, the green layer of the future head and inside a white, spongy receptacle. The smell of young eggs is weak, radish-like; the mature fruiting body gives off a strong, sickly sweet, carrion-like smell, noticeable from a distance. Do not taste it.

Spore print and spores

Spores pale yellow, oblong-elliptical, smooth. Size: 3–5 × 1.5–2.5 µm (descriptions give different ranges). The spores are in the slimy gleba, not in a classic spore print.

Habitat and distribution

Ecology. Associated with decaying wood (a saprotroph), mycorrhizal relationships with some trees are also possible. The smell attracts flies (including Calliphora vicina, Lucilia caesar, Lucilia ampullacea, Dryomyza anilis), which eat the gleba and spread the spores in their droppings; beetles also visit the fruiting bodies, but contribute less to dispersal. A possible link with badger setts has been described. Fruiting bodies may appear in forests, parks, thickets and mulched gardens.

Distribution. Temperate zone of the Northern Hemisphere, also South America and Asia; common in Poland, except at higher mountain elevations. In 1983–2004 it was under species protection in Poland, now it is not legally protected.

Fruiting. From summer to late autumn.

What can it be confused with?

• Phallus hadriani (dune stinkhorn) — Egg covering slightly violet or pinkish, smell weaker.
• Morchella esculenta (common morel) — A mature stinkhorn with the gleba eaten away is sometimes confused with it, but it has a white, spongy receptacle and a strong carrion smell, and the morel has no slimy mass.
• Puffballs (eggs of young fruiting bodies) — The egg covering of the stinkhorn consists of two layers with a gelatinous mass between them, and in cross-section the beginnings of the fruiting body can be seen.

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 species name impudicus means "shameless" in Latin; the genus name comes from a Greek word meaning the male sex organ.
• The fruiting body grows extremely fast: growth of 10–15 cm per hour has been measured, and a growing fruiting body can exert a pressure of up to 1.33 kPa, enough to break through asphalt.
• In 1983 the stinkhorn was placed under species protection in Poland, as one of the first 20 fungus species, because people often destroyed the fruiting bodies; the protection was lifted in 2004 because the species is widespread.
• The smell contains, among others, hydrogen sulphide, methanethiol and dimethyl trisulfide.