Hen of the Woods Identification Guide

The First Thing You See

You are almost always standing at the foot of a large oak when this one registers, and what registers first is a shape rather than a mushroom. From several metres away Grifola frondosa reads as a grey-brown cushion, or a ruffled pile of feathers, sitting low in the leaf litter against the swell of the trunk. It is rarely at eye level and it is rarely small: a typical clump is the size of a football, and a good one can be the size of a laundry basket.

Look down, not up. Check the collar where the trunk flares out into its buttress roots, then widen the search a metre or two into the litter, because clumps frequently appear well away from the bole, apparently straight out of bare soil. They are not; they are attached to a root running just under the surface.

The colour scheme is muted - fawn, mouse-grey, dull tan, sometimes almost olive-brown - darker over the middle of each lobe and paler towards the edges. In a dry spell the whole mass looks matt and dusty and blends into the litter perfectly. After rain it darkens and the fine radial streaking on each lobe becomes obvious.

Reading the Rosette

Kneel down and turn the clump slightly so you can see how it is put together. The architecture is the identification. What you have is a rosette of many small overlapping caps - dozens, often well over a hundred - each one spoon-, tongue- or fan-shaped, roughly 2-7 cm across and only a few millimetres thick, all radiating outward and upward from one shared point of origin.

No individual cap is circular, and no individual cap has a stalk of its own in the middle. Each one narrows backwards into a flattened, tapering branchlet, and those branchlets run together lower down.

With a hand lens the upper surface of a single lobe is dry and finely radially fibrillose: fine hair-like lines run from the attachment outward to the rim. Many lobes also show faint concentric zoning, grey alternating with brown. The margin is thin, wavy, often shallowly lobed or split, and in young specimens it is inrolled and noticeably paler, sometimes nearly white.

The Underside: Pores, Not Gills

Turn a lobe over. There are no gills at all. The undersurface is a smooth white to cream layer that, under a lens, resolves into a dense field of minute pores - about one to three per millimetre, round to faintly angular, thin-walled and even. The tube layer beneath them is shallow, only a millimetre or two deep.

The detail that matters most is where the pore layer stops. It does not stop at the back edge of the cap. It runs decurrently down the branchlet and keeps going onto the stalk system below, so the entire branched skeleton of the clump is sheathed in pores. Run a thumb from the rim of one lobe inwards and downwards: if the white pore surface fades gradually onto the branch rather than ending in a clean line, the structural plan is right.

The pore surface is white to cream when fresh, dulling to buff or dingy tan with age. Firm handling leaves at most a faint brownish smudge after several minutes. It does not blacken.

The Branched Stalk and the Point of Attachment

Cut the clump free low down and look at the cut face. Trace the branchlets downward and you will see them fuse repeatedly into thicker, whitish, cartilaginous branches, and finally into a single short, thick, off-white to pale tan basal stem that is usually buried in litter or soil. That single base is the giveaway: everything above it is one organism, not a colony of separate mushrooms crowded together.

Scrape the litter away and follow the base down. It will be fixed to a root, a root collar, or the buried remains of one. It is never simply rooted in loose soil with nothing beneath it.

Flesh and Colour Change

The flesh is white throughout. In the caps it is thin, soft and slightly fibrous; in the branches it becomes denser and stringier, with a grain that runs lengthwise. There is no latex and no gel layer.

Cut a lobe cleanly across and watch it for a quarter of an hour. It stays white, or at most dulls very slowly to a pale buff. There is no rapid darkening, no red, no blue, no black. This unchanging white flesh is one of the most useful characters you have, because the nearest look-alike fails it dramatically.

Taking a Spore Print

Cut one lobe with its pore layer intact and lay it pore-side down on white paper, ideally with a strip of dark paper or foil underneath half of it so a pale deposit shows up. Cover it with an upturned cup or bowl to keep the humidity up and the draughts out, and leave it somewhere cool for four hours to overnight.

The print is white, occasionally with the very faintest cream tint. Deposits from a mature clump can be heavy enough to leave a visible dusting on the litter around the base. Under a microscope the spores are smooth, colourless, broadly ellipsoid to ovoid with a small apiculus, about 5-7 x 3.5-5 microns, and they do not react with iodine.

Substrate, Position and Season

Grifola frondosa is a white-rot agent of the roots and lower trunk of broadleaf trees. Oaks are the classic partner by a wide margin; beech, maple, elm, hornbeam and sweet chestnut also occur. Conifers do not. Fruiting runs from late summer into autumn, typically triggered by a soaking rain after a warm spell, and a colonised tree will produce in the same place year after year - so it is worth noting the tree, not just the mushroom.

Position on the tree is diagnostic in itself: base of trunk, between buttress roots, or over a shallow root some distance out. If a comparable rosette is growing high on a standing trunk or out of a fallen log lying on the ground, reconsider.

Separating It From the Other Big Basal Polypores

Giant polypore (Meripilus giganteus / M. sumstinei) is the one that catches people out. It also grows in a rosette at hardwood bases, but the individual caps are far fewer and far bigger - often 10-30 cm - and, decisively, it blackens. Press the pore surface with a fingernail or cut the flesh and within a few minutes the mark turns smoky grey and then black. Dried specimens go almost charcoal. Grifola never does this.

Berkeley's polypore (Bondarzewia berkeleyi) is also a rosette at oak bases, but everything about it is coarser: caps much larger and thicker, cream to tan rather than grey-brown, flesh thick and tough enough that a knife meets real resistance, and pores conspicuously bigger and ragged - often 1-2 mm and irregularly angular rather than fine and even.

Umbrella polypore (Polyporus umbellatus) shares the branched common base but builds it differently: each cap is small, circular and centrally stalked, with a little navel-like dimple in the middle, so the clump looks like a bouquet of miniature parasols rather than a pile of overlapping tongues. It is whiter and greyer and arises from an underground tuber-like sclerotium.

Chicken of the woods (Laetiporus spp.) is not really confusable once seen - bright sulphur-yellow to orange, in thick broad shelves, usually part way up a trunk - but it occupies similar trees.

Cauliflower fungus (Sparassis spp.) forms a comparable pale mass at tree bases, but its lobes are flattened ribbons or leaf-like blades with a completely smooth undersurface. No pores anywhere. It also favours conifer bases.

A Working Sequence

1. Confirm the position: base or shallow roots of a standing broadleaf tree.
2. Confirm the rosette of many small overlapping stalkless tongues from one base.
3. Confirm fine white pores that run decurrently onto the branches.
4. Press and cut, and confirm no blackening.
5. Take a white spore print.
6. Note the host tree so you can check the same spot next autumn.