Hemlock Varnish Shelf Identification Guide

The First Impression

The Hemlock Varnish Shelf is one of the few fungi that looks artificial. Growing from a dead hemlock trunk, a mossy conifer log or a rotting stump in eastern North American forest, it forms a broad kidney-shaped shelf whose upper surface is glossy mahogany-red, as though several coats of varnish had been brushed on and left to harden. Around the outside runs a soft white to yellow band, the growing margin, which gives young specimens a striking two-tone look: cream at the edge, orange in the middle, deep blood-red at the point of attachment.

When you meet one you are usually in damp, shaded conifer forest, often in a hemlock ravine or a stream valley, in late spring or early summer. Fruitbodies grow singly, in small overlapping groups, or in a stack down the side of a dead trunk. Sometimes they emerge from wood buried under moss, which can make them look deceptively as though they were growing from the ground.

Reading the Upper Surface

The shelf is 5 to 20 cm across, occasionally 30 cm, and 1 to 4 cm thick, kidney-shaped, fan-shaped or roughly semicircular, sometimes irregular and lumpy where growth has been obstructed. In many collections there is a lateral or off-centre stalk, thick and short, joining the shelf to the wood; in others the fruitbody is attached directly, without a stalk. Where a stalk exists it wears the same lacquered finish, usually darker, red-brown to almost black.

The crust is the key. It is smooth, hard and strongly shining, and it feels like polished plastic under a fingertip. Colour grades from whitish or pale yellow at the extreme margin through orange-yellow and orange-red to mahogany, chestnut and finally dark red-brown or blackish near the attachment, with concentric bands and shallow furrows recording growth pauses. The white margin disappears once growth stops, leaving a uniformly dark, glassy shelf. Old specimens dull slightly and often collect a rust-brown film of their own spores, which can be wiped off to reveal the shine beneath.

The Pore Surface

Underneath, the fertile surface is a flat layer of minute pores, white to cream when fresh and ageing to pale buff or dull tan. Look with a lens and count roughly 4 to 6 pores per millimetre, round and even. Draw a fingernail across the surface: the scratch turns brown within a minute or two, so you can write on a fresh specimen. That prompt brown bruising against a white ground is a good confirmation.

The tube layer beneath is 0.5 to 2 cm deep, pale cream to buff, and there is only one layer. This is an annual fungus that builds a single set of tubes and does not add a new layer each year, which distinguishes it from the perennial shelf fungi that show stacked tube layers in section.

Sectioning the Flesh

Cut the shelf in half from margin to attachment with a strong knife. The context above the tubes is white to pale buff or pale tan, soft and spongy-corky when fresh, drying light, fibrous and punky. It is much softer than it looks; a fresh specimen cuts almost like cork board, and a young growing margin can be dented with a fingernail. There may be faint concentric fibrous zoning but no bands of dark tissue and no black crustose lines. Just under the varnish is a thin hard rind, and the boundary between rind and soft white context is sharp in section.

There is no latex, no strong colour change beyond a slight darkening of the cut surface, and the smell is mild and woody or slightly fungal.

Taking a Spore Print

Ganoderma species print heavily and you can often skip the paper: in summer the moss, bark and lower shelves beneath a fruiting specimen are dusted with cocoa-brown powder. To print deliberately, cut a section with the pore layer intact, prop it pore-side down over white paper with a small gap for airflow, cover it and leave overnight. The deposit is rusty brown to cinnamon-brown.

Under a microscope the spores are distinctive and confirm the genus at once: ellipsoid with a truncated end, double-walled, with a brown, minutely spiny or pillared inner wall visible through a smooth colourless outer wall.

Substrate, Season and Ecology

Substrate is a genuine identification character here, not background detail. This species fruits on conifers, above all eastern hemlock, and also on other conifer wood including spruce, fir and pine. It grows on dead standing trunks, fallen logs, cut stumps and the wounds of weakened living trees, and it causes a white rot in which lignin is broken down and the residual wood is left pale, soft and fibrous. It functions mostly as a decomposer of dead conifer wood and sometimes as a weak parasite on stressed trees.

Its distribution is centred on eastern and northern North America, following the range of hemlock. Fruiting begins in late spring, often May or June, earlier than most bracket fungi, and continues into summer. Because the fruitbodies are annual and fairly soft, by winter they are usually blackened, insect-riddled and collapsing.

Separating It from Look-alikes

The lacquered Ganoderma species are the main comparison, and substrate does most of the work.

Ganoderma sessile and Ganoderma lucidum in the broad sense grow on hardwoods, particularly oak, maple and other broadleaves, and are usually attached directly or with a short stub rather than a well-developed lateral stalk. Their context is generally darker, cinnamon-buff to pale brown rather than white, and often firmer. A varnished red shelf on a hardwood stump in the east is far more likely to be one of these; a varnished red shelf on hemlock is this species.

Ganoderma curtisii, another hardwood species, tends toward yellow to ochre tones on the crust and has a mottled, often paler stalk.

Ganoderma applanatum, the Artist's Conk, is perennial and completely different in finish: the upper surface is dull, matt, grey-brown and crusty, never varnished, and the section shows several stacked tube layers and a firm brown context often flecked with white. Its white pore surface also bruises brown, so use the crust and the layered tubes rather than the bruising to separate them.

Fomitopsis pinicola grows on conifers and can show a shiny red-black band near the attachment, but its crust is resinous and concentrically banded in red, black, grey and cream rather than uniformly lacquered, it is perennial and hard as wood, it causes a brown rot in which the wood crumbles into cubes, and its context is pale and tough. A knife point will barely dent it, while a fresh Hemlock Varnish Shelf gives easily.

The Trametes brackets, including Turkeytail, are thin, leathery and hairy or velvety above with no lacquer at all, and they yield white spore prints.

Field Checklist

Annual kidney-shaped shelf on conifer wood, most often hemlock; upper surface glossy and varnished, mahogany-red with a white to yellow growing margin; often a lateral lacquered stalk; white to cream pore surface bruising brown, 4 to 6 pores per millimetre; a single tube layer over soft white context; rusty brown spore print; fruiting late spring through summer and causing a white rot.