Hen of the Woods

Hen of the Woods (Grifola frondosa) forms one of the largest and most architecturally complex fruiting bodies in temperate woodland. From a single thick base at the foot of a tree, a whitish stalk branches repeatedly, and each branch tip flattens into a small fan or spoon-shaped cap. Dozens or hundreds of these caplets crowd together into a rounded, ruffled mass that can reach a metre across and weigh many kilograms, with the overlapping grey-brown caps resembling the ruffled feathers of a sitting hen.

Grifola is a small genus in the Polyporaceae characterised by exactly this compound, branched, many-capped construction. Related compound polypores such as Meripilus and Polyporus umbellatus achieve similar bulk with different geometry, and telling them apart is largely a matter of reading how the caps attach to the branching stalk.

The species is a specialist of old oaks. It reappears on the same tree in the same spot autumn after autumn, sometimes for decades, because the underground mycelium is established in the root plate and lower trunk and is effectively permanent once in place.

Fruiting body

A large compound rosette, 15-60 cm or more across, made up of a branched whitish stalk system arising from a single thick basal stem. Each ultimate branch flattens into a caplet. The whole cluster is broadly fan-shaped or globose and often deeply lobed.

Caps

Individual caplets are 3-10 cm across, spoon-shaped, tongue-shaped or fan-shaped, with a wavy, often lobed or split margin. The upper surface is grey-brown, mouse-grey, tan or olive-brown, frequently faintly zoned in concentric bands and radially fibrillose or streaked. Caps darken with age and dry out at the edges. They are attached laterally or eccentrically to the branches.

Pore surface

White to cream, ageing pale buff, running down (decurrent) from the underside of each caplet onto the supporting branch, so that the branches themselves are partly clothed in pore surface. Pores are small and angular, roughly 1-3 per millimetre, in a shallow tube layer 1-3 mm deep.

Flesh & spore print

The flesh is white, fibrous and firm, and remains white when cut without notable staining. The stalk system is tough and pale. The spore print is white.

Grifola frondosa grows at the base of standing trunks, on exposed root buttresses and on old stumps, overwhelmingly of oak. It is also recorded from beech, sweet chestnut, elm, maple and other broadleaves. It is a fungus of mature and veteran trees, so it is often found in old parkland, wood pasture, hedgerow oaks and long-established woodland rather than young plantations.

Fruiting is firmly autumnal, generally from early autumn through to the first hard frosts, with a single large flush per tree per year. The species is widespread in temperate Europe, in eastern North America where old oak woodland is extensive, and across temperate East Asia including Japan and China, where it has a long history of cultivation on hardwood substrate.

The fungus is a weak parasite and subsequent saprotroph, causing a white rot of the butt and root wood of its host. Its mycelium digests lignin along with cellulose, leaving the affected wood pale, soft and fibrous. Because it works on the root plate and lower trunk, long-established infections gradually reduce the anchoring strength of a veteran tree, and the fungus goes on decaying the stump and root system for years after a tree comes down.

A well-established mycelium is effectively permanent within its host, which is why a known tree can be relied on to produce a rosette in the same place each autumn over many seasons. The species is one of the compound polypores that solve the problem of building a very large spore-producing surface without a massive single bracket: by branching and producing many small caps, it exposes far more pore area to moving air than a single shelf of the same weight could.

Giant Polypore (Meripilus giganteus) grows in the same position at the base of beech and oak and reaches a similar size, but its caps are far fewer and much broader, its colouring is a warmer ochre to yellow-brown, and every part of it bruises and ages blackish within minutes of being handled, which Grifola never does. Umbrella Polypore (Polyporus umbellatus) has round caps that are centrally rather than laterally attached, each on its own distinct little stalk, and it arises from an underground sclerotium rather than directly from a tree base.

Chicken of the Woods (Laetiporus sulphureus) is unmistakable by colour, forming a few large flame-orange shelves with sulphur-yellow pores high on the trunk. Cauliflower Fungus (Sparassis crispa) grows at the base of pines and is built from flattened, wavy, ribbon-like cream lobes with a smooth fertile surface and no pores at all.