Stalked Lattice Stinkhorn Identification Guide

The First Impression

Warm weather, a day or two after heavy rain, and a mulched flower bed, a manured field margin or a well-fed lawn. Something red-orange is standing about a hand's height above the ground, and there are flies on it. Walk closer and the structure resolves into two clearly separate parts: a long, pale, spongy stalk, and perched on top of it a rounded head made of fused arms forming a closed net, with dark olive slime lying in the meshes.

Nothing else in the fungal world is put together quite like that. The identification of a stinkhorn is essentially a matter of architecture, and here the architecture is: a distinct stalk, plus a spherical latticed head that does not break apart into free arms.

The Egg Stage

Half the time you find the species before it has erupted, and the egg is worth dissecting because it is diagnostic in itself.

Eggs are ovoid to nearly spherical, 2-4 cm across, whitish to buff or faintly pinkish, partly buried in the substrate, and attached at the base to a white cord-like rhizomorph that runs off into the mulch. The outer skin is tough and slightly leathery.

Slice one from top to bottom with a sharp blade and examine the layers. Outside is the thin skin; beneath it a thick, clear gelatinous layer that feels like stiff jelly; and inside that, tightly folded and compressed, the whole future fruit body — the concertina-folded spongy stalk below, and above it the compacted head with a dark olive-brown band of spore slime, the gleba, already formed. That cross-section, showing a folded receptacle rather than a uniform interior, separates a stinkhorn egg from any young puffball at a glance.

The Mature Fruit Body

Expansion is fast, often overnight, driven by water uptake that inflates the pre-formed chambers.

The stalk. The mature fruit body stands 5-15 cm tall, most of that being stalk. It is hollow, spongy and chambered, its wall built of a honeycomb of pits and cavities that you can see clearly by tearing a piece lengthwise. It is roughly cylindric, tapering slightly upward, and its colour ranges from white through cream and yellow to orange or pinkish, often deeper in colour toward the top where it meets the head. The texture is soft, moist and easily crushed, and the whole structure collapses within a day or two.

The volva. At the base, the remains of the egg persist as a whitish membranous cup or sac gripping the bottom of the stalk, usually partly buried, with the white rhizomorph still attached below it. Excavate rather than pull, because that volva confirms the stinkhorn architecture.

The head. This is the character that names the species. Sitting on the top of the stalk, and continuous with it rather than detachable, is a rounded to nearly spherical head, typically 2-4 cm across, formed of thick arms that are fused into a closed lattice — a net of red, orange-red or scarlet bars enclosing polygonal windows. The head does not open into separate free arms, and it does not sit directly on the volva. The transition from pale stalk to coloured head is abrupt.

The gleba. The spore mass is olive to dark olive-brown or almost blackish, slimy, and smeared over the inner and upper faces of the lattice bars. It is strongly and unpleasantly fetid. Flies arrive within minutes of expansion, feed on the slime and carry spores away on their bodies and in their guts, so by the second day the head may be picked clean, leaving a bare orange net that is easier to photograph and far easier to interpret structurally.

How to Read the Spores

There is no spore print in the usual sense here. The gleba is a deliquescing slime rather than a dry powder, and no amount of covering a cap with a bowl will produce a deposit.

Instead, take a trace of gleba on a needle or blade tip, smear it thinly on a slide in a drop of water, and examine it. The spores are very small, smooth, cylindrical to elliptical, hyaline individually and roughly 3.5-5 x 1.5-2 micrometres. The olive-brown colour you see with the naked eye comes from the mass, not from any single spore. If you want a record without a microscope, photograph the fresh gleba colour and the bare lattice separately.

Substrate, Season and Ecology

This is a saprotroph of rich organic matter. Typical substrates are bark and wood mulch in landscaped beds, compost, straw, manured or heavily fertilised soil, cultivated field margins, greenhouse beds, and nutrient-rich lawns. It is not attached to wood in the way a bracket fungus is, and it forms no partnership with living plant roots.

It is a warm-weather fungus, most abundant in summer and in warm-temperate to subtropical regions, and it fruits in flushes a few days after heavy rain. Fruit bodies commonly appear in small scattered groups where the mycelium has colonised a mulched bed, and the same bed may produce repeatedly through a wet season.

The ecology of dispersal explains all of the strange morphology. Rather than releasing dry spores to the wind, the fungus advertises with bright colour and a powerful odour, presents its spores as a sticky insect-friendly slime, and lets flies and beetles do the transport work.

Separating the Look-Alikes on Morphology

Clathrus ruber. A hollow latticed sphere as well, but with no stalk whatsoever: the entire net sits directly on the volva at ground level, and the gleba lines the inner faces of the lattice bars.

Clathrus columnatus. Two to five thick spongy columns rise from the volva and are joined only at the very top, forming an arch rather than a net; there is no single unifying stalk and no closed lattice.

Lysurus mokusin. Closest in general plan, since it has a definite stalk. However, its stalk is distinctly angular and fluted with four to six longitudinal ribs, and the head consists of separate erect arms that are pressed together and fused only near their tips, opening outward with age instead of forming a closed spherical net.

Lysurus cruciatus and Aseroe rubra. Both have a stalk topped by arms that splay outward like the rays of a star or the arms of an anemone, never a closed lattice ball.

Phallus species. A thimble-shaped or conical head that is clearly a separate cap sitting on the stalk apex, its surface pitted, ridged or honeycombed and covered in gleba, sometimes with a lacy skirt hanging beneath it.

Mutinus species. Slender, tapering, spongy stalks with no differentiated head at all: the gleba is simply smeared over the coloured upper portion.

Young puffballs (Lycoperdon, Calvatia) and earthballs (Scleroderma). These can be confused with the egg stage above ground, but a vertical cut resolves it immediately: puffballs are uniformly white and cottony inside when young, earthballs have a firm pale rind and a marbled dark interior, and neither contains a folded receptacle or a gelatinous layer.

Quick Field Checklist

• Warm season, days after heavy rain, on mulch, compost, manured ground or rich lawns
• Egg stage whitish, partly buried, with a white rhizomorph; cut it to reveal a gelatinous layer and folded receptacle
• Mature body 5-15 cm tall with a hollow, spongy, chambered stalk
• Head spherical and latticed, red to orange, closed and continuous with the stalk
• Olive-brown slimy gleba in the meshes, strongly fetid, quickly removed by flies
• White membranous volva at the buried base
• No conventional spore print; examine gleba smear for tiny cylindrical spores