Columned Stinkhorn Identification Guide

The First Encounter

Columned Stinkhorn is a fungus of disturbed, warm, cultivated ground, and the usual encounter is not in wild woodland at all but in a garden bed, a mulched shrub border, a lawn edge, a plant nursery, a park verge or the wood-chipped surround of a municipal planting, in the warm months and within a day or two of rain. In subtropical and tropical regions it can appear at almost any time; in warm-temperate areas it is a summer and early autumn fungus.

You usually smell it before you find it. A sharp, foul, carrion-like odour hangs around the spot, and following it leads to an object that does not look like a mushroom at all: two to five thick, spongy, orange to scarlet-orange arms rising vertically from a whitish sac in the ground, curving together and joining at the top into an arch or a narrow, columned cage. Flies are usually clustered at the summit, which is itself part of the field signature.

The design registers immediately as one of the cage or lattice stinkhorns. The genus impression is: no cap, no gills, no ordinary stipe, an emergence from a soft egg, a spongy chambered receptacle, and a dark slimy spore mass carried on the structure rather than beneath it.

The Egg Stage

Half the identification work can be done underground, and it is worth digging. Before expansion, the fungus is a whitish to pale pinkish or dirty-cream egg, roughly 2-4 cm across, subglobose to slightly pear-shaped, sitting at or just below the soil or mulch surface. Attached to its base are one or more thick white cords, the rhizomorphs, running away into the substrate; these are conspicuous in this group and worth noting when you lift the egg.

Slice an unopened egg vertically with a sharp knife and read the section. Outermost is a thin tough skin, the peridium; inside that lies a thick, clear, gelatinous layer; and folded inside the jelly is the compressed, undeveloped receptacle - already orange or pinkish - with the dark olive-brown spore slime, the gleba, packed against the surfaces that will become the inner faces of the columns. Recognising this layered egg construction confirms the group even when no mature fruit body is present, and the colour of the folded receptacle inside the jelly is an early species clue.

Reading the Mature Structure

An expanded fruit body stands about 4-8 cm tall, occasionally more in ideal conditions. Its structure is the whole identification, so read it deliberately.

First, count the arms. There are usually three or four, sometimes only two, occasionally five. They are thick, spongy and chambered - break one and the section shows a coarse foam of open cells, like a stiff bath sponge - and each stays roughly the same thickness for most of its length rather than tapering sharply to a point.

Second, check where the arms begin. This is the critical point of the identification. In Columned Stinkhorn the arms rise separately, straight out of the volva, with no common stalk beneath them. Push the debris away from the base and you should be able to see each column entering the white sac independently. There is no cylindrical stem of any length carrying a crown of arms.

Third, check where the arms end. They arch inwards and fuse at the apex, so the whole structure is closed at the top into a single arch or a slender columned cage with elongated vertical windows between the arms. They do not stand free and separate at the top, and they do not form a rounded network of many small polygonal meshes over the whole surface.

Colour and Surface

The columns are bright orange, orange-red or scarlet, sometimes paler, pinkish-orange or apricot towards the base and stronger towards the apex. The surface is finely pitted, wrinkled or minutely honeycombed from the chambered internal structure, and it is dry to slightly moist to the touch but not viscid except where the gleba touches it.

At the base sits the volva: a whitish to pale grey or faintly pinkish sac, the ruptured remains of the egg, often half-buried and holding a little jelly, with the white rhizomorphs running from beneath it. Always check for and describe the volva, because its presence is fundamental to the group.

Reading the Gleba

The spore mass is dark olive-brown to blackish-brown, slimy and adhesive, and it is carried on the inner faces of the columns, concentrated in the upper part of the structure near and around the point of fusion. On a fresh specimen the slime is a glossy dark smear on the inside of the arch; on an older one, after the flies have worked it over, the columns are clean, bright orange and bare, which is why weathered specimens look like empty orange arches and are often not recognised.

The odour is central to the biology. It is strong, fetid and carrion-like, and it is produced by the gleba, not by the columns themselves. A specimen whose gleba has already been removed by insects may smell of very little.

Spores and Why a Print Does Not Work

This is one of the few groups where the standard spore print technique does not apply. There is no cap to lay face down and no hymenium that sheds a dry deposit; the spores are embedded in slime and are exported by insects rather than dropped into still air. Attempting a print gives nothing useful.

Sample directly instead. Take a scrape of the gleba on a knife tip, smear it thinly on a slide with a drop of water and examine it. The spores are very small, smooth, colourless to pale olive, narrowly ellipsoid to cylindrical, in the region of 3.5-4.5 by 1.5-2 micrometres, and they occur in enormous numbers. Their tiny size and cylindrical shape are consistent across the stinkhorn group and confirm the family placement if the field structure was ambiguous.

Substrate, Season and Ecology

Columned Stinkhorn is a saprotroph of decaying plant material in soil, with a marked preference for rich, disturbed and cultivated ground: wood-chip mulch, bark beds, compost-enriched borders, sandy lawns, nursery containers, planting beds and roadside plantings. It is not a fungus of deep undisturbed forest litter, and mulch is the single most productive place to search.

Its distribution is warm-climate: the southeastern United States, Central and South America, parts of Africa, and introduced populations in Australia and elsewhere, with the mulch and nursery trade widely credited for moving it into new areas. Fruiting is triggered by warmth plus rain, and a fruit body has a short life - it can expand from an egg in a few hours and be reduced to a collapsing orange rag within a day or two.

Its ecological role is twofold: it decays plant debris in the soil, and it uses insects rather than wind for spore dispersal. Flies, beetles and ants come to the odour, feed on the slime and carry spores away on their bodies and through their guts, which is why the fruit body invests in bright colour, an elevated structure and a powerful smell instead of in gills or pores.

Separating It from Look-alikes

Latticed Stinkhorn, Clathrus ruber. Also red-orange and also arising from an egg with no stalk, but it forms a rounded, hollow, closed lattice of many polygonal meshes over the entire fruit body, like a red wiffle ball, rather than a small number of vertical columns joined only at the top. If you can count more than about six windows, it is not Columned Stinkhorn.

Stinky Squid, Pseudocolus fusiformis. The closest confusion, since it also has three or four orange arms fused at the apex. The separation is at the base: Pseudocolus has a definite short white stalk rising out of the volva from which all the arms spring, whereas the columns of Clathrus columnatus arise separately and directly from the volva itself. Pseudocolus arms are also more slender and taper noticeably towards the tip.

Lysurus species, including the lantern stinkhorns. These have a long, obvious, often ribbed or fluted stalk carrying short arms at the top; the arms are usually free at the tips or only loosely touching, and the gleba is smeared across the arms and the head. The presence of a substantial stalk rules out Columned Stinkhorn.

Starfish Fungus, Aseroe rubra. Has a short stalk and a flat radiating star of arms, each of which splits into two slender tips, with the gleba in a dark central disc rather than on the inner faces of vertical columns.

Common stinkhorns, Phallus and Mutinus species. Have a single unbranched white or pink stalk topped by a distinct head or cap carrying the gleba, so no cage or arch is formed at all.

Work the sequence - egg with rhizomorphs, no common stalk, a small number of thick spongy orange columns rising separately from the volva and fused only at the apex, gleba on the inner upper faces - and Columned Stinkhorn is straightforward to pin down even when the structure has partly collapsed.