Oak Mazegill Identification Guide

First Impressions and the Setting

You almost always meet Daedalea quercina on oak, and often on oak that a person cut. The classic finds are the sawn face of an oak stump in a park or wood-pasture, the underside of a fallen oak trunk, and, very characteristically, worked oak: gate posts, fence rails, sleepers, old field-gate stumps and stacked cordwood. It is a species you can find in a car park as easily as in ancient woodland.

The first impression is of weight and hardness. This is a thick, pale, corky shelf sitting tight against the wood, greyish and lumpy on top and looking rather unpromising and weathered. Push a thumbnail into it: it barely dents. Only when you crouch and look at the underside does the fungus become interesting.

Reading the Upper Surface

Brackets are sessile with no stem at all, broadly attached, semicircular to hoof-shaped, 5-20 cm wide, projecting 3-10 cm from the wood and 2-8 cm thick at the attachment. They are usually solitary or in a short row, occasionally almost resupinate on the underside of a log.

The upper surface is pale wood-brown, buff, greyish-ochre or straw, weathering to dull grey and very often carrying a green film of algae on older specimens. It is uneven, knobbly and lumpy, with broad shallow concentric ridges rather than the crisp, contrasting bands of a Trametes. It is dry, corky and roughened, never varnished, never brightly coloured and never zoned in strong stripes. Old brackets become deeply furrowed and cracked.

The Underside: The Whole Point

Turn the bracket over, or get your head under it, because this is where the identification is made.

The pores are not round. They are elongated, sinuous slots and irregular labyrinthine channels, 1-3 mm across and up to several millimetres long, meandering across the surface. Near the margin they can become almost gill-like, drawn out into radiating plates, while towards the attachment they are more maze-like and closed.

Look at the walls between them. They are thick, 0.5-1.5 mm, blunt-edged and solid, not thin blades. That thickness is worth training your eye on, because it is the main character against several thin-walled maze-pored relatives. The colour is pale wood-buff to cream and stays pale; it does not bruise or darken when scratched.

Flesh, Section and Colour Change

Cut a bracket vertically with a strong knife. Two things stand out.

First, the flesh is homogeneous with the pore layer: the same pale wood-buff colour and the same corky texture run continuously from the upper surface right down into the tube walls, with no abrupt boundary, no black line beneath the surface layer and no contrasting duplex structure.

Second, it is genuinely tough. Flesh is 1-3 cm thick and shaves like dry softwood rather than cutting like a mushroom. There is no colour change on cutting, bruising or scratching, and no distinctive smell beyond a faint dry woody odour.

Growth is persistent rather than strictly annual. A bracket can survive more than one season, adding new tube layers underneath while the upper surface greys and roughens, which is why so many finds look old and battered.

Taking a Spore Print

Printing a hard bracket takes patience and the right timing. Choose a fruit body with a pale, fresh, actively growing margin, which in practice means spring through autumn rather than midwinter.

Either hold a sheet of black card under the growing margin for several hours in situ, or cut a wedge and stand it pore-surface downwards over black card in a closed box with damp tissue overnight. The deposit is white and sparse, so black backing is essential and old weathered brackets may give nothing at all.

Microscopically the spores are cylindrical to narrowly ellipsoid, smooth, colourless and non-amyloid. The white print is mostly a confirmation that you are in the right broad group rather than a species character; the maze-pores and the host do the real work.

Substrate, Season and Ecology

Daedalea quercina causes a brown rot in the heartwood of oak, breaking the wood into brown cubical blocks that crumble between the fingers. It is a saprotroph of dead oak: stumps, fallen and standing dead trunks, large fallen limbs, and seasoned worked timber. Sweet chestnut is an occasional alternative host; other trees are rare enough that a maze-pored bracket on birch or willow should send you to the look-alike list at once.

Fruit bodies are present in every month. New growth appears at the margin in late summer and autumn, and old brackets persist through winter and beyond. The tie to oak is one of the strongest anchors in the identification, so identify the tree before you identify the fungus.

Separating It From Look-Alikes

Lenzites betulina has true radiating gills, thin plates rather than thick-walled slots, and the bracket is thin, 3-8 cm, with a densely hairy upper surface usually greened by algae. It favours birch and other hardwoods, and its flesh is white and thin.

Daedaleopsis confragosa has elongated maze-like pores but they are thin-walled, and the bracket is much thinner and flatter with a zoned reddish-brown upper surface. Its pore surface often darkens where scratched. It grows mainly on willow and birch.

Trametes gibbosa is whitish with a distinct hump at the point of attachment and an upper surface commonly green with algae. Its pores are elongated radially but regular, thin-walled and slot-like in a neat way rather than labyrinthine, and it grows chiefly on beech.

Cerrena unicolor is thin, greyish and hairy, with maze-like pores that break down into teeth, and, decisively, a thin black line visible in section between the hairy upper layer and the flesh. Oak Mazegill has no such line.

Gloeophyllum sepiarium has true gills but is thin, rusty-brown and grows on conifers.

Fomes and Phellinus species are hard and perennial with small round pores and a dark, contrasting context.

The triage question is short: gills or slots, thick walls or thin, and what tree? Thick-walled labyrinthine slots in a heavy corky bracket on oak is Daedalea quercina.

Field Checklist

Thick corky sessile bracket on oak or worked oak timber; pale buff to greyish lumpy upper surface with broad shallow ridges; underside of thick-walled sinuous maze-like slots 1-3 mm wide; pale wood-coloured homogeneous flesh continuous with the tube walls; no colour change; white sparse spore print; brown cubical rot; present year-round.