Hericium abietis Identification Guide

The Setting You Find It In

This is a conifer-forest fungus and the setting does half the identification. You are typically in mature or old-growth stands of true fir, spruce, hemlock or Douglas-fir in western North America - the coastal ranges, the Cascades, the northern Rockies - walking past big downed logs and standing snags in late summer or autumn. Hericium abietis does not appear in the litter and it does not appear on hardwoods. It appears on wood, and usually on large wood.

The first impression is of something white hanging where nothing white should be. It commonly erupts from a knot scar, a broken branch stub, the sawn end of a log, or a crack in the bark of a fallen fir, so it often projects sideways or hangs downward from a vertical face rather than sitting on top of anything. Size is startling: a modest specimen is the size of two fists, a good one can be 30-70 cm across and heavy enough to sag off the log under its own weight.

Colour when young is a clean white with a faint creamy or salmon-pink cast in the deeper shadows of the branch system. With age and sun it yellows, going cream, then buff, then a dingy ochre-tan; old specimens brown from the tips inward.

The Overall Architecture

Get the whole shape clear before you look at any detail, because the genus Hericium is separated almost entirely on architecture.

H. abietis is a branched fungus. From a tough, dense, whitish basal core attached to the wood, a framework of branches divides repeatedly, spreading outward and downward into an open, coral-like or shrub-like mass. The branches are round to slightly flattened in cross-section and can be several centimetres thick near the base, thinning steadily outward.

Hanging from those branches - chiefly from the tips and from the undersides of the branch arms - are the spines. They occur in clusters and tufts rather than in a single continuous curtain, so the specimen has a repeating unit: a branch, ending in a spray of spines, repeated dozens of times over. Standing back, the effect is of many small icicled pompoms carried on one shrub.

Reading the Spines

The spines are the spore-bearing surface, and they replace both gills and pores.

Take a single tuft in your fingers. Individual spines are soft, pliant, tapering to a fine point and typically 0.5-2 cm long, occasionally reaching 3 cm on a well-fed specimen in shade. They all hang more or less straight down under gravity, whatever the orientation of the branch that carries them - this is worth checking, because it means spines on a sideways-projecting branch point down, not outward.

Under a lens the surface is smooth and slightly waxy-looking; there are no pores, no ridges and no gill folds anywhere on the fungus. Colour matches the branches: white ageing cream, and the tips brown first.

Stipe, Base and Attachment

There is no stipe in the ordinary sense. Instead there is a basal mass - a short, thick, tough, often slightly rooting core that is wedged into the wound or crack in the wood. Cut into it and you will find it markedly denser and tougher than the branches, sometimes almost woody, and often stained brownish or discoloured by the substrate.

Follow the attachment. It should go into solid conifer wood: the heartwood of a log, the sawn face of a stump, or the exposed interior of a snag. Trace it far enough to be sure you are on wood and not on a buried root of something else.

Flesh and Colour Change

Cut a branch across. The flesh is white, moist, fibrous and slightly stringy along the grain, becoming tougher and more rubbery towards the base. It stays white. There is no latex, no gel and no rapid staining; the cut face may slowly discolour to cream or pale tan over an hour or more, and old or frost-touched specimens brown generally, but there is nothing sudden. A specimen that reddens, blues or blackens on cutting is not a Hericium.

Taking a Spore Print

Cut off a well-spined branch tip and lay it on its side on white paper, or suspend it spines-downward over a sheet, and cover it to hold humidity. Give it several hours; older, drying specimens can be reluctant.

The print is white. This on its own separates the toothed fungi as a group from several branched look-alikes with coloured deposits. Under the microscope the spores are small - roughly 5-6.5 x 4.5-5.5 microns - subglobose to broadly ellipsoid, colourless, minutely roughened, and amyloid, meaning they turn blue-grey in Melzer's reagent. That amyloid reaction plus the rough wall is a genuine confirmation if you have a scope.

Substrate, Season and Ecology

Hericium abietis is a wood decayer of conifers. It produces a white pocket rot in the heartwood of firs above all, and also spruce, hemlock and Douglas-fir, entering through wounds, broken tops and cut surfaces and working through the trunk interior for years before ever fruiting. The fruit body you find is the visible end of a long internal decay column.

That ecology explains where it appears: at wounds, scars, breaks and cut ends, on large-diameter downed logs and standing dead trunks, and sometimes high up a snag out of reach. It fruits from late summer through autumn and into early winter in mild coastal weather, and a productive log will often produce again in following seasons from the same or an adjacent wound.

Separating It From the Look-alikes on Structure Alone

Lion's mane (Hericium erinaceus) is unbranched. It is one solid, rounded cushion - a shaggy white ball - with all its spines, which are long (2-5 cm), hanging as a single beard from the underside of that one mass. It grows on broadleaf trees: oak, beech, maple, walnut. Branched framework versus single cushion is the whole distinction, and it is unmistakable in the hand.

Coral tooth (Hericium coralloides) is branched, like abietis, but the branches are flatter and more delicate and the spines are short - usually well under a centimetre - and arranged in rows along the underside of the branches rather than in dense tufts at the tips. The result looks like a lattice or an open filigree rather than a shrub hung with pompoms. It is a hardwood species, typically on beech, birch and maple logs.

Bear's head tooth (Hericium americanum) is the eastern North American branched species with long spines in terminal tufts, and it is genuinely close in build to H. abietis. Substrate separates them cleanly in practice: americanum on hardwood in eastern forests, abietis on conifer in western ones. Its spines also tend to be longer and more evenly tapered.

Northern tooth (Climacodon septentrionalis) carries spines, but it is built as a tier of thick shelving brackets fused at one point on a standing hardwood trunk, tough and fibrous, with spines only on the underside of each shelf. It is a bracket with teeth, not a branched coral.

Crown coral (Artomyces pyxidatus) and the true corals (Ramaria spp.) are branched and pale, but they have no spines at all: Artomyces has distinctive little crowns at each branch tip, and Ramaria has upward-pointing, smooth-surfaced branches. Run a finger over the underside of a branch - if it is smooth rather than bristling, you are not in Hericium.

Field Checklist

1. On conifer wood - a log, snag or stump, at a wound or cut face.
2. A branched framework from one tough basal core, not a single cushion.
3. Spines 0.5-2 cm in tufts at branch tips and undersides, hanging vertically.
4. White ageing cream to buff; white unchanging flesh.
5. White spore print; spores minutely rough and amyloid if you can check.