Ghost Fungus Identification Guide

The find

Autumn or early winter in southern Australia, a few days after solid rain. You are walking past the base of a dead eucalypt, an old stump, or a fallen trunk lying in leaf litter, and there is a pale, nested cluster of fan-shaped brackets bursting out of the wood. From a distance they look creamy white. Close up they are far more interesting: the cream is stained and streaked with grey, smoky purple, bruise-blue and dark brown, and the pigment radiates outwards from the point where the fungus grips the wood, like ink spreading through paper.

The growth habit is the second thing to register. This species builds in tiers and rosettes. Individual caps overlap, share a fused base, and curl in on one another, so that a large fruiting looks like a shelf of nested shells or a stack of shallow funnels tipped sideways. A big cluster can be 30 cm or more across and heavy enough to feel substantial when lifted.

Reading the cap

Each cap is 5 to 20 cm wide, occasionally larger, and its shape depends on where it sits on the cluster. Caps arising from the side of a vertical trunk are fan-shaped or kidney-shaped and laterally attached. Caps growing from the top of a stump or from buried wood are more nearly circular and become funnel-shaped or vase-like, sunken deeply at the centre.

The surface is dry, smooth, and faintly silky, sometimes with fine appressed fibres. The margin starts inrolled and neat and becomes wavy, lobed and often split in older specimens. Colour is the great character: an off-white to cream ground, overlaid with grey, olive-grey, purplish-brown, blue-black or almost violet tones concentrated near the attachment and fading outwards. Very young caps can be nearly uniformly pale; very old ones can be sombre and dark overall. That dark, cool-toned mottling is the thing to fix in memory.

The gills

Turn a cap over and the underside is decisive. The gills are true gills, thin and blade-like, and they are strongly decurrent, running a long way down whatever stem there is and often continuing right onto the wood or into the fused base of the cluster. They are crowded, narrow, deep front to back, and they radiate cleanly from the attachment point.

Colour is white to cream in youth, sometimes picking up faint grey or ochre tints with age, occasionally shading dull orange-cream at the very base where the pigment from the cap bleeds through. Edges are even, not serrated or torn. Short gills of several lengths are interspersed between the full-length ones.

This is also the surface to test for the character the species is famous for, described below.

Stipe, base and flesh

There is usually a stem, but it is short, thick, eccentric or fully lateral, and it tapers downwards into the substrate. Caps at the top of a rosette may have almost no stem at all; caps low on the cluster have the most obvious ones. Several stems commonly merge into a single tough basal mass welded to the wood.

Slice a cap in half from margin to base. The flesh is white and stays white; it is thin near the margin and thickens towards the stem, with a soft but slightly fibrous texture. It does not redden, blacken or blue on cutting. The smell is faintly fungal and slightly sour or sweetish, nothing pronounced.

The glow

The gills of fresh, actively sporulating fruitbodies emit a soft greenish-white light. This is genuine bioluminescence produced by the living mycelium and hymenium, and it is the most memorable confirmation available, but it has to be observed properly.

Take a fresh specimen into complete darkness. Not dim light, not dusk with a streetlamp, complete darkness. Sit still for a full ten to fifteen minutes so your eyes dark-adapt, and hold the gills up in front of you. The glow is faint, cool green, strongest along the gill faces, and it fades in old or drying material. Photographs need long exposures. If you see nothing, do not immediately reject the identification: the fruitbody may be past its best, too dry, or too young. A positive glow is strong evidence; a negative result is inconclusive.

Taking a spore print

Cut a cap free of the cluster, lay it gills-down on black paper or on a strip of dark card, cover it with a bowl to trap humidity, and leave it several hours or overnight. Fresh caps drop heavily and the print builds fast.

The deposit is white to very pale cream. Use dark paper, because a white print on white paper is nearly invisible. Heavy natural spore deposits are often visible in the field as a pale dusting on the caps of lower brackets in a tiered cluster, which is a useful shortcut.

Substrate, season and ecology

This is a wood-decay fungus. It fruits on dead and dying hardwood, overwhelmingly eucalypts, and also on Banksia, Acacia, Casuarina and a range of introduced hardwoods in gardens and parks. It grows from stumps, fallen trunks, standing dead wood, exposed roots and buried debris, sometimes appearing to come out of soil when the wood is underground.

It is a white-rot organism, breaking down lignin as well as cellulose so that the remaining wood becomes pale, fibrous and stringy. It behaves largely as a saprotroph but can colonise the heartwood of living trees, so a fruiting at the base of an apparently healthy eucalypt is not unusual.

Distribution is southern and eastern Australia, including Tasmania, with records from Western Australia. Fruiting peaks in autumn and winter after rain, and the clusters can persist for several weeks, gradually darkening and drying.

Separating look-alikes on morphology

Oyster mushrooms (Pleurotus species) are the main confusion. They are shelf-like on wood with decurrent whitish gills, but the cap is a plain grey, tan, buff or brown without the cool purple-black mottling, the flesh is thicker and more succulent, the gills are broader and less deeply decurrent, and the caps are more flatly shelf-like rather than nested funnels. They do not glow.

Panellus stipitis and related small species also luminesce, but they are a fraction of the size, tan to buff, with a tiny lateral stem, and they crowd densely on hardwood branches in tiny brackets rather than forming large rosettes.

Lentinellus species have conspicuously serrated, jagged gill edges and tougher flesh.

Hohenbuehelia and Resupinatus species are small, gelatinous in the flesh layer, and stemless.

Northern-hemisphere Omphalotus species such as O. olearius and O. illudens share the nested habit and decurrent gills but are vivid orange throughout, and they do not occur in Australian eucalypt forest.

Field summary

Hardwood substrate, nested tiers of fan or funnel-shaped caps, cream ground marbled with grey and purple-black, deep crowded white decurrent gills, short eccentric stem, unchanging white flesh, white spore print, and a greenish glow in true darkness. That set is not shared by anything else growing on Australian eucalypts.