Maitake

Grifola frondosa forms one of the most recognisable structures in temperate woodland: a rounded, cabbage-like mass 20–60 cm wide made of dozens of overlapping, spoon- or fan-shaped grey-brown caps, all arising from a repeatedly branched white stalk anchored at the base of a tree. The layered, feathered outline is behind the English name Hen of the Woods.

It is a true polypore — the spore-bearing surface is a layer of minute tubes ending in pores on the underside of each frond, not gills. Unlike the hard bracket fungi, however, Grifola is soft and fleshy, and the whole rosette grows, matures and decays within a few weeks.

The genus sits in the Grifolaceae and is distinguished from other clustered polypores by its combination of a single central branching stalk, greyish-brown zoned fronds with wavy margins, decurrent white pores, and its habit of returning to the same tree root system autumn after autumn.

Fruiting body

The whole rosette is 20–60 cm across (occasionally far larger) and weighs from a few hundred grams to several kilograms. It consists of many individual caps, each 4–10 cm wide, that are spoon-, fan- or tongue-shaped with a wavy, often lobed and slightly frilled margin. Cap surfaces are dry, faintly radially fibrous and vaguely zoned in bands of grey, greyish-brown, tan and olive-brown, usually darker at the centre of each frond and paler toward the edge.

Pores

The underside of every frond carries a thin white to cream pore layer that runs down onto the branch supporting it. Pores are small but visible to the eye, roughly 1–3 per millimetre, angular to slightly irregular, and stay white or become faintly yellowish with age. They do not blacken when handled.

Stalk

A thick white central stalk emerges from the soil or root collar and divides repeatedly into flattened branches, each branch ending in a cap. Sliced across, the stalk is solid, white and slightly fibrous. The whole structure detaches as one piece from its point of attachment.

Flesh and spore print

The flesh is white, soft and fibrous when young, becoming tough and stringy with age, and does not change colour when cut or bruised. Odour is pleasantly earthy or nutty. The spore print is white, and mature clusters often dust the leaf litter and any lower fronds with a fine white bloom.

Maitake grows at the base of living or recently dead broadleaf trees, overwhelmingly on oak, and less often on beech, elm, maple, chestnut and hornbeam. It appears at the root collar, in the crotch between buttress roots, or a short distance from the trunk directly over a buried root, which can make it look deceptively terrestrial. Mature, veteran trees in open woodland, parkland and wood pasture are its typical setting.

The season runs from late summer into late autumn, usually beginning after the first sustained cool, wet spell and continuing until hard frost. The species is widespread across temperate Europe, eastern and central North America, and East Asia including Japan and China, where it also grows on sawdust-based substrate under cover. A colonised tree commonly produces a rosette in the same place for many years running.

Grifola frondosa is a weak parasite that becomes a saprotroph, causing a white butt rot in the roots and lower trunk of its host. Its enzymes break down lignin along with cellulose, leaving the affected heartwood pale, soft, spongy and eventually hollow, while the outer sapwood and the tree's crown may remain functional for decades. Colonised veteran oaks therefore often stand and leaf out normally for many years while quietly becoming hollow at the core.

That hollowing has ecological consequences beyond the fungus: decayed root buttresses and cavities create habitat for insects, bats and hole-nesting birds. The fruiting body itself is short-lived — a rosette expands over one to two weeks, sheds spores from its pore layer, and collapses into a blackening mass that is quickly broken down by flies and beetles, while the mycelium persists in the wood.

Meripilus giganteus, the Giant Polypore, is the commonest confusion. Its fronds are much larger and fewer, broadly fan-shaped rather than spoon-shaped, and a distinctly warmer yellow-brown, and crucially every part of it — pores, flesh and cap edge — stains black or blackish-brown where rubbed or bruised, which Grifola never does. Bondarzewia berkeleyi builds a similar rosette but of very large, pale cream to buff fronds with coarse, jagged, much bigger pores and extremely tough flesh.

Polyporus umbellatus shares the branched stalk but its caps are small, circular and attached centrally like little umbrellas rather than one-sided fans, giving a bouquet of round discs. Laetiporus species are unmistakable by colour, forming bright orange and sulphur-yellow shelves directly on the trunk with no branched stalk at all. Comparing frond shape, pore size and whether a bruise blackens will separate all four.