Common Stinkhorn

The Common Stinkhorn is one of the strangest fungi of temperate woodland and a rare case where the nose finds the organism before the eye does. It develops underground as a soft white 'egg', a gelatinous sphere the size of a hen's egg, then in a matter of hours the stalk inside elongates dramatically and thrusts the spore-bearing head into the air.

The mature fungus consists of a hollow, brittle, white, spongy stalk 10-25 cm tall carrying a bell- or thimble-shaped cap that is honeycombed with ridges and pits. That cap is coated in a thick olive-green to blackish slime, the gleba, which contains the spores and produces the powerful carrion-like odour detectable many metres away.

Phallus belongs to the Phallaceae in the order Phallales, a group that has entirely replaced wind dispersal with insect dispersal. The whole architecture - rapid growth, elevated head, sticky spore slime, strong scent - is built around recruiting flies as couriers.

Egg stage

A whitish to pale pinkish, soft, rubbery ball 3-6 cm across, half-buried in litter or soil, attached below by a stout white mycelial cord. Cut vertically, it shows a gelatinous jelly layer surrounding the compressed, folded, immature stalk and the dark olive gleba layer over the developing cap - a distinctly layered cross-section with a visible mushroom-in-miniature at its core.

Stalk

On emergence the stalk expands rapidly, sometimes within a few hours, to 10-25 cm tall and 2-4 cm thick. It is pure white, hollow, and built of a brittle, honeycombed, foam-like tissue that snaps rather than tears. The base retains the ruptured remains of the egg as a loose, sagging white to pinkish volva.

Head

A thimble- to bell-shaped cap 2-5 cm tall sits on the stalk apex, its surface raised into a network of chambered ridges and pits like a honeycomb or a small morel. When fresh it is entirely masked by a thick olive-green to dark brown mucilaginous gleba. There is a small white perforated disc at the very tip of the cap.

After the flies

Once insects have removed the slime, the underlying cap surface is revealed as clean white or cream and clearly pitted, and at this stage the odour largely disappears.

Spore print and odour

Spores are carried in the slime rather than deposited as a print; the gleba is olive-brown. The odour is strong, sweetish and putrid, carrying a considerable distance in warm weather.

Phallus impudicus grows in woodland of many kinds, especially where there is rich leaf litter, wood chip, buried rotting wood, old stumps or accumulated humus. It is equally at home in gardens, shrubberies, parkland, hedgerows and mulched borders, and it is often abundant in conifer plantations and in sandy soils among pine and birch.

The eggs form underground during summer and autumn and can emerge from midsummer to late autumn, most often after warm humid weather. Groups frequently arise along the line of a buried root or a decaying stump, sometimes in impressive numbers. The species is common and widespread throughout temperate Europe, and occurs in North America and Asia.

The Common Stinkhorn is saprotrophic, its mycelium forming thick white cords that permeate leaf litter, wood chip and buried decaying wood. In this role it is a significant decomposer of woody debris in soil, and gardens with fresh bark mulch often see sudden colonisation as the fungus exploits the new resource.

Its dispersal biology is the striking part. Rather than releasing dry spores to the wind, it invests in a sugary, sticky, strongly scented spore slime. Blowflies, flesh flies and beetles are drawn from a distance, feed on the gleba, and depart with spores stuck to their bodies and passing intact through their guts, to be deposited elsewhere. A stinkhorn can be stripped clean within a day of emerging, which is why so many finds are white, pitted and already odourless. The rapid stalk expansion is achieved not by cell division but by the sudden inflation of pre-formed cells with water, one of the fastest growth rates known in the fungal kingdom.

The Dog Stinkhorn (Mutinus caninus) is much slenderer and smaller, with an orange to pinkish stalk and a tapering, poorly differentiated head bearing a smaller patch of olive slime, and it lacks the honeycombed thimble cap. Phallus hadriani is very similar in form but arises from a distinctly pink to violet egg and favours coastal dunes and sandy ground.

The Devil's Fingers or Octopus Stinkhorn (Clathrus archeri) emerges from a similar egg but opens into four to seven bright red arms spread like a starfish, with the slime borne on their inner faces. The Latticed Stinkhorn (Clathrus ruber) forms a hollow red spherical cage. Egg-stage stinkhorns can resemble puffballs or Amanita eggs, but a vertical cut shows the gelatinous layer and the dark olive gleba over a folded stalk - puffballs are uniformly white and solid inside, and Amanita eggs show a young cap with gills.