Maitake Identification Guide

Look at the Base of the Tree, Not the Ground

Maitake is not found by scanning leaf litter. It is found by walking up to old trees and looking at the point where the trunk meets the soil. The classic setting is autumn in an ancient oak wood, a wood pasture or a parkland avenue: a big, mature or over-mature oak, its buttress roots swelling out of the turf, and, sitting against the trunk or a metre out over a root, a large greyish rosette the colour of dead leaves.

That colour match is why so many people walk past it. From five metres a fruitbody can read as a pile of fallen leaves or a lump of weathered bark. Size varies from the diameter of a dinner plate to something you cannot lift with one hand, occasionally 50-60 cm across and several kilograms in weight. Once you have found one tree that produces it, note the tree, because the mycelium is perennial and the same trunk often fruits for many years running.

Step One: Read the Architecture

The most important character is structural, not colour. Grifola frondosa is a compound fruitbody. From a single short, thick white base, buried at the soil surface or wedged against the bark, a system of white branches divides again and again, and each final branch tip flattens out into a small cap. Those caps overlap in tiers like the petals of a huge grey rosette, and a good specimen can carry more than a hundred of them.

Grasp the whole thing gently and it lifts as one object. Nothing about it is woody or leathery: it is soft-fleshed and slightly springy, and it tears rather than snaps.

Step Two: The Individual Caps

Each caplet is 2-8 cm across and only a few millimetres thick. The shape is spoon-like, tongue-like or fan-shaped, attached laterally or eccentrically to its branch, with a wavy, lobed and often notched or split margin.

The upper surface is dry and matt, finely wrinkled, and marked with radial fibrillose streaking that catches the light; it is not smooth and glossy, and it is not concentrically zoned in strong bands. Colour is grey-brown, mouse-grey, olive-brown or tan, generally darker where the cap meets its branch and paler, sometimes almost cream, at the outer margin. Specimens developing in deep shade are paler; those in the open darken.

Step Three: The Pore Surface

Turn a caplet over. There are no gills. The fertile surface is a layer of tiny pores, white to cream when fresh and yellowing with age.

The key detail is where the pores stop, which is nowhere. They run decurrently down off the underside of each cap and continue along the branch that supports it, so the branch itself is fertile for part of its length. Under a lens the pores are angular and irregular, roughly 1-3 per millimetre, becoming elongated, torn and maze-like where they run down the stems. The tube layer is shallow, only 1-3 mm deep.

Press and bruise the pore surface with a fingernail, then wait five minutes. In Grifola frondosa nothing dramatic happens: the surface may dull slightly or go faintly yellowish, but it does not turn black. Hold that observation, because it is the single most important separator from its closest look-alike.

Step Four: Branches, Base and Flesh

The branches are white to pale cream, tough-fleshed and solid, flattening progressively as they approach the caps. They converge on a short, thick, white basal stem that often sits partly buried, attached to a root or to the root collar of the tree. Excavate carefully to see that attachment; it is worth knowing whether the fruitbody comes from the trunk base, a buttress root or a buried root running out into the surrounding soil.

Cut through a branch. The flesh is white throughout, fibrous, and does not change colour beyond a slight cream or pale yellowish tone on drying. There is no latex, no gel, no coloured zone and no rind. Dried material becomes hard, light and pale.

Taking and Reading a Spore Print

A whole cluster is far too big to print. Cut a single fresh caplet with a short section of its branch, and lay it pore-side down on black paper or a dark tile, because the print is white and will vanish on white stock. Cover it with a bowl and leave it for four to twelve hours in a still place.

Choose your material carefully: a mature but not decaying cluster with a bright white, moist pore layer will print readily, while an old, dry, yellowing cluster may give almost nothing. Under a microscope the spores are smooth, hyaline, broadly ellipsoid to ovoid, about 5-7 by 3.5-5 microns, and not amyloid. Clamp connections are present on the generative hyphae.

Substrate, Season and Ecology

Grifola frondosa is a white-rot fungus of the root collar and butt of broadleaf trees, overwhelmingly oak, and also recorded on sweet chestnut, beech, lime, elm and maple. It behaves as a weak parasite and then as a saprotroph, colonising heartwood in the base of the trunk and in the root plate, breaking down lignin as well as cellulose so that the decayed wood becomes pale, soft and fibrous.

Fruiting is triggered by cool, wet weather from late summer into late autumn, most often September and October in temperate regions. Fruitbodies appear at the trunk base, on stumps of felled hosts, or apparently from bare ground where a buried root runs, sometimes a metre or more from the trunk. Because the decay column persists in the tree for many years, the same host produces year after year, often in the same spot on the same side of the trunk.

Separating the Closest Look-alikes on Morphology

Meripilus giganteus, the Giant Polypore, is the most important comparison and the reason for the bruise test. It also forms a huge rosette at the base of a broadleaf tree, but its caps are far larger, 10-30 cm each, fewer in number, broadly fan-shaped, cream to tan and often concentrically zoned. Decisively, every part of it stains black within a few minutes of being bruised, and the whole fruitbody blackens on drying. It is most often at beech. Grifola frondosa does not blacken.

Polyporus umbellatus has smaller caps that are circular and centrally stalked, each with a shallow navel in the middle rather than a lateral attachment, in a more open, dichotomously branched cluster arising from a buried black sclerotium. Its caps are paler buff and its pores whiter.

Bondarzewia berkeleyi is thicker and coarser: a few very large, fleshy, cream to pale buff caps rather than many small grey ones, with markedly bigger pores, often 1-3 mm wide, on oak. Its spores are globose and ornamented.

Laetiporus sulphureus is unmistakable once seen: bright orange to salmon above with a sulphur-yellow pore surface, forming thick fleshy brackets on the trunk rather than a branched rosette at the base.

Sparassis crispa grows at the base of pines and consists of flattened, crisped, cream ribbons with no pore surface at all.

Trametes and other bracket fungi are thin, tough and leathery, attached directly to the trunk without a branching stem system.

Hericium species hang spines rather than pores and are usually white.

Field Checklist

A large branched rosette at the base of an oak; many small grey-brown, radially streaked, fan- or spoon-shaped caplets; white to cream angular pores that run down onto the branches; white fibrous flesh; short thick white basal stem attached to root or root collar; no blackening on bruising; white spore print; late summer to late autumn, recurring on the same tree.