Reishi Identification Guide

First Impression And Setting

Reishi announces itself with a surface no other bracket quite matches. The upper crust looks lacquered — a hard, glossy, resinous skin in mahogany, chestnut and oxblood tones, banded with concentric zones and finished with a soft white or bright yellow band at the actively growing edge. Against dark bark and damp leaf litter it looks polished, almost artificial.

The setting is low and shaded: the base of a living hardwood, a cut stump, a partly buried root, or a log lying in deep leaf litter. Look at ankle height around oak, maple, beech, elm and other broadleaved trees in temperate woodland, in parkland and along woodland margins, from early summer through autumn. Because it often arises from buried roots, a bracket can appear to grow straight out of the ground several feet from the nearest trunk — trace it back and you will find wood.

Young fruit bodies begin as pale knobs or fingers, so a first find may be a cluster of white to yellow clubs that only later flatten into brackets. Do not dismiss those; return in two weeks and they will be shelves.

Reading The Cap

Mature caps are 5 to 25 cm across and 1 to 3 cm thick, kidney-shaped, fan-shaped or nearly circular, and often shallowly lobed or irregular where two brackets have fused.

Test the crust with a fingernail: it is hard and shell-like, not corky or fibrous. It carries a genuine varnished shine when fresh, sometimes so glossy it reflects the sky. Older, weathered specimens dull as falling spores coat the surface with rusty-brown powder — wipe a patch with a damp cloth and the gloss usually reappears beneath.

Colour is zoned in bands running parallel to the margin: pale cream or white at the extreme edge, then yellow or orange, then progressively deeper reddish-brown, chestnut and mahogany toward the point of attachment. The white marginal band is a growth zone and disappears once the season's expansion stops, so late-autumn material is uniformly dark.

Look also for a lateral stalk. Classic material is stipitate: a distinct hard, varnished, reddish-black stem, 3 to 15 cm long, attaches to the side or occasionally the centre of the cap, often twisted or bent. In humid, oxygen-poor spaces the fungus may instead produce antler-like unbranched or forked columns with no cap at all. Where the fungus grows directly on a large stump, the bracket may be broadly attached and effectively stalkless.

Reading The Pore Surface

Turn a bracket over, or crouch to look under it. The underside is a smooth, flat, poroid surface — no gills, no teeth, no wrinkles.

Fresh material is white to cream. Press it firmly with a fingertip or draw a fingernail across it and watch: the touched area discolours to dull brown or cinnamon within seconds to a minute, and the mark persists. This bruising reaction, and the fact that you can write on a fresh cap's underside, is a good confirmatory test.

With a hand lens, count pores across a millimetre — expect roughly 4 to 6, tiny and round, with entire mouths. Slice the bracket vertically and the tube layer appears as a distinct pale brown band 0.5 to 2 cm deep, sitting beneath the flesh. In this species that tube layer is a single stratum: one season's growth, not stacked layers.

Flesh, Section And Colour Change

Cutting is essential, and it needs a stout knife or a saw for older material. In vertical section you should see three zones: the thin dark crust, then the flesh, then the tubes.

The flesh is white to pale tan or pale wood-brown, sometimes with faint darker zoning, and it is fibrous and soft-corky when fresh, hardening considerably as it dries. It does not contain white chalky pockets, and it should not be dark chocolate-brown. There is no dramatic colour change in the cut flesh itself beyond a slow dulling.

Odour is faint and slightly resinous or woody. Texture is a better guide than smell: fresh material can be sliced with effort; a season-old bracket resists a blade entirely.

Taking A Spore Print

You rarely need to arrange a print, because a productive bracket prints itself. Look at the leaf litter, moss, bark and lower stem immediately beneath a mature specimen: a fine rusty cocoa-brown to cinnamon dust settles there, sometimes coating the upper surface of the bracket itself and any neighbouring vegetation.

If you want a clean deposit, cut a section of bracket with intact tubes and rest it pore-side down on white paper under a bowl for a few hours. The colour is a warm brown, never white, never black, never purple. Under a microscope the spores are distinctive — ellipsoid, truncated at one end, and double-walled with an ornamented inner wall — but the field-level point is simply that the deposit is brown.

Substrate, Season And Ecology

This is a wood decayer. It causes a white rot, breaking down lignin as well as cellulose and leaving the residual wood pale, soft and stringy. It attacks the roots and butt of living hardwoods as well as dead stumps and fallen trunks, and a bracket at the base of a standing tree indicates internal decay of the root plate.

Fruit bodies are annual: a fresh crop is produced each season, and old brackets blacken, weather and disintegrate over a year or two rather than adding a new tube layer. Peak production is early summer to autumn in temperate zones, following warm humid weather.

Hosts are predominantly broadleaved trees — oak above all, plus maple, elm, beech, plum and other hardwoods. Growth on conifers should immediately prompt a second look at the species.

Separating It From Look-alikes On Morphology

Hemlock Varnish Shelf (Ganoderma tsugae). Very similar varnished crust and white pore surface, but it fruits on conifers, especially eastern hemlock, and its flesh is white and softer, drying more chalky and lightweight. Substrate is the practical field character: conifer versus hardwood.

Ganoderma sessile and the sessile hardwood group. Share the shiny mahogany crust and brown print, but are typically broadly attached to the substrate with little or no lateral stalk. Check for a well-developed stem.

Ganoderma curtisii. Also stalked and varnished, but shows conspicuous yellow to golden tones in the crust and margin, and its flesh often contains resinous darker bands visible in section.

Artist's Conk (Ganoderma applanatum). Immediately separable: the upper surface is dull, matte, crusty and greyish-brown with no varnish, the bracket is perennial with multiple stacked tube layers visible in section, and the flesh is dark chocolate-brown, frequently with white chalky pockets. Its white pore surface bruises brown just as readily, so use the crust and the layered tubes rather than the bruising test.

Resinous Polypore (Ischnoderma resinosum). Soft, velvety and unvarnished, with a dark brown to blackish upper surface and a broad white margin, and it lacks any hard shell-like crust.

Fomitopsis and Laetiporus species. Neither is varnished; the former are hard and perennial with pale zoned crusts, the latter are bright orange-yellow, soft and lack a lateral stalk.

A Quick Field Sequence

1. Bracket at the base of a hardwood stump, root or log, low to the ground.
2. Upper surface hard, glossy and varnished, zoned mahogany with a white or yellow growing edge.
3. Lateral hard varnished stalk present in classic material.
4. Underside white to cream, bruising brown on contact, 4 to 6 tiny round pores per millimetre.
5. Section shows pale tan fibrous flesh over a single tube layer.
6. Rusty cocoa-brown spore dust on the litter beneath.