Split Gill Identification Guide

First Impression on a Dead Branch

Split Gill is a fungus you learn to spot by scale and posture. Look along fallen hardwood branches, cut stump faces, storm-snapped limbs still hanging in the canopy, timber stacks, fence rails and even bundled straw, particularly where the wood is exposed to sun and wind rather than lying in damp shade. The fruit bodies are small, 1 to 4 cm across, attached sideways to the wood with no stem or only a narrowed stem-like point of attachment, and they usually appear in rows and overlapping troops rather than singly. Each is fan-shaped, shell-shaped or in tight groups almost rosette-like, with a lobed, wavy or scalloped margin. From above the colour is whitish, pale grey or greyish-buff, and the whole upper surface is densely hairy, so a colony looks like a line of tiny felted fans stitched along a dead branch.

One behavioural detail is worth knowing before you even touch it. In dry weather the fans shrivel, curl inward and look dead; after rain they rehydrate within hours and resume the flexible, expanded shape they had before. If you return to the same branch across a season you will see the same fruit bodies switch between the two states repeatedly.

Reading the Upper Surface

Run a fingertip over the top of a fan. It is densely tomentose, covered in fine matted hairs that give a felt or suede feel, and the hairs are usually paler than the flesh beneath. Colour ranges from off-white through grey to pale buff or greyish-brown, and older specimens often go greenish where algae settle on them, exactly as they do on tough bracket fungi. The margin is thin, strongly lobed and often inrolled. There are no concentric colour zones like a turkeytail, and no varnish or gloss anywhere.

Reading the Underside: the Decisive Character

Turn a fan over and use a hand lens. The underside carries radiating fold-like structures that fan out from the point of attachment and look at first glance like gills. They are typically pinkish-grey, lilac-grey, or buff to pale tan, and they are thick, blunt and rather waxy-looking compared with the thin blades of a true gilled mushroom. Now look at each fold edge closely. Every fold is split lengthwise down its outer edge into two halves, and in dry conditions those halves roll apart and curl back over the fold surface, closing the fertile tissue away from the air. Rehydrate the specimen with a drop of water and the two halves unroll and flatten out again over the following minutes. Nothing else you are likely to meet on dead wood does this, and once you have watched the fold edges open and close the species becomes unmistakable for life.

Flesh, Texture and Cutting

Pinch a fan between finger and thumb. The flesh is thin, tough and leathery, pliable when wet and hard and brittle when dry, and it is white to greyish in section. It does not bruise to a different colour, exudes no milk or liquid, and shows no colour change on cutting. Slicing a fan vertically from attachment point to margin shows a thin fibrous layer of flesh with the fold tissue hanging below it and the hairy layer above, without a distinct tube layer or any pore structure. That leathery, unchanging, thin-fleshed section rules out the soft and fleshy oyster-type fungi immediately.

Taking a Spore Print

Prints are possible but need patience and a fully rehydrated specimen, because a dry fan with rolled-back folds is not shedding at all. Soak a fresh fan for an hour or leave it in a humid box until the folds have opened, then cut it from the wood with a sliver of substrate and prop it fold-side down over black paper under a cover, ideally overnight. The deposit is white to very pale cream and often sparse. Since the fold structure alone settles the identification, treat the print as confirmation rather than as the main test.

Substrate, Season and Ecology

Split Gill is a decay fungus of dead hardwood, working through the wood of fallen branches, dead attached limbs, cut stump surfaces, sawn timber, and occasionally palms, straw and other tough plant material. It is strongly associated with exposure: sunlit, drought-prone wood suits it because its drying-and-reviving fold mechanism lets it survive conditions that would kill softer fungi, and it fruits in situations where competitors cannot persist. It is found on every inhabited continent and is one of the most widely distributed fungi known, so the same fan shape appears on dead wood from temperate hedgerows to tropical plantations. Fruiting is possible all year wherever there is enough moisture, with flushes after rain rather than a single defined season.

Separating the Look-alikes

Crimped gill, Plicaturopsis crispa, is the nearest visual match. It grows on hazel, beech and birch twigs, has a distinctly zoned ochre to orange-brown upper surface, and its underside carries crimped, wrinkled, vein-like folds that are wavy but never split lengthwise. Its colour alone separates it in most cases.

Birch mazegill, Lenzites betulina, and the resupinate-to-bracket Trametes species have elongated gill-like or maze-like pore structures, but those plates are single and entire, the fruit bodies are larger and more rigid, and the upper surface is usually concentrically zoned.

Curtain crust and Stereum species share the hairy upper surface and leathery texture but have a smooth or merely wrinkled undersurface with no radiating folds at all.

Panellus stipticus is small, buff to tan, with a short lateral stem-like base and true thin crowded gills, and its flesh is thinner and more pliable rather than felted above.

Oysterlings, Crepidotus species, are soft, moist, white to pale cream, with true thin gills and a brown spore print, and they collapse quickly rather than drying and reviving.

Anything with genuine pores rather than folds, such as Trichaptum or Schizopora, is excluded by structure the moment you use a lens.

Field Checklist

Small stemless hairy fan on dead hardwood; whitish to grey felted upper surface with a lobed margin; underside with radiating fold-like structures split lengthwise and rolled back when dry; tough leathery thin flesh with no colour change; revives fully when wetted; white spore print; present year-round on sun-exposed wood. The split, rolling folds are worth confirming every time, because they carry the identification single-handedly.