Tiger Sawgill Identification Guide

The Setting You Are Standing In

Tiger Sawgill is a fungus of water margins and sunlight. The classic find is on a bleached hardwood log stranded on a river bar, on exposed willow or cottonwood roots along a bank, on flood-scoured driftwood, or on the cut end of a poplar stump in an open, sunny clearing. Unlike most gilled fungi, it does not wait for the damp shade of autumn: it fruits in late spring and summer, often in dense clustered troops of a dozen or more fruitbodies erupting along a crack in the wood.

The first impression at a distance is of something small, pale and tough — a cluster of little cream funnels flecked with dark, and stems that look wiry rather than fleshy. Pick one and the impression is confirmed by feel. Where an ordinary gilled mushroom crushes softly, this one resists; the cap flexes, the stem twists rather than snapping, and the whole thing feels more like thin hide than like a mushroom.

Reading the Cap

Caps run roughly 2 to 10 cm across. They begin convex with an inrolled margin, then flatten and quickly become depressed at the centre, and in mature specimens they are deeply funnel-shaped — you can look straight down a well-defined hollow into the top of the stem.

The ground colour is whitish, cream or pale buff. Laid over it are the scales that give the species its name: small, flattened, radially arranged tufts of dark brown to blackish fibrils, densest and darkest in the centre of the cap and becoming sparser and more streak-like toward the edge. On some specimens the scales are so concentrated centrally that the middle of the cap reads as almost black against a pale rim. They are appressed, meaning they lie flat rather than standing up as shaggy points.

The surface is dry at all times. The margin is thin, often wavy, and frequently splits radially as the cap expands in sun and wind — split margins are normal on older material and should not put you off.

The Gills

Turn the fruitbody over and look closely, ideally with a hand lens; this is where the identification is won.

The gills are decurrent — they run distinctly down the stem rather than stopping at it — narrow, crowded, and white to cream when fresh, dulling to buff or with brownish edges as they age or where handled. What separates the sawgills from almost everything else is the gill edge itself: under a lens it is not smooth but finely and irregularly toothed, like the edge of a saw blade or a torn strip of paper. Run a lens along several gills to confirm; the serration can be subtle on very young material and becomes clearer with age.

The gill trama is tough. Push a fingernail across the gills and they bend and spring back instead of shattering, which immediately excludes the brittlegills and separates this from most soft-fleshed woodland species.

Stipe, Base and Flesh

The stipe is central to slightly off-centre, 2 to 8 cm long and 3 to 10 mm thick, usually tapering downward, and often curved where the fruitbody has bent toward light. It carries the same pale ground colour with darker brown fibrils and small scales, generally strongest in the lower half. It is solid, tough, and does not break cleanly; twist it and it shreds into fibres.

At the base, look for how the stipe attaches. Fruitbodies commonly arise in clusters from a shared point or from a line along the wood, and the very bottom of the stem is often darker brown and may be slightly rooting into a crack.

The flesh is thin, white and remarkably tough — pliant and leathery rather than fragile. Cut it and it stays white; there is no blueing, reddening or blackening, though old or handled tissue may slowly go dingy buff. Dried fruitbodies become hard and horn-like and can revive partially in rain, which is why weathered specimens persist on logs for weeks.

One genuine oddity is worth knowing. Tiger Sawgill sometimes produces a closed, secotioid form in which a persistent white membranous veil covers the gills entirely, so the fruitbody looks like a small pale puffball on a scaly stem. Slice one lengthwise and you will find the sawtoothed gills hidden inside, still attached to the stem, which resolves the puzzle at once.

Taking a Spore Print

Tough-fleshed species can be slow to drop spores, so choose a young, fully expanded cap, cut the stem flush, and lay the cap gills-down on dark card beside white paper. Cover it with a box over a damp tissue and leave it overnight rather than the usual few hours.

The print is white, occasionally with the faintest cream tint. This single result eliminates the scaly brown-spored species that share the clustered, scaly look — anything dropping rusty brown or ochre is not a sawgill.

Substrate and Season

This is a white-rot decayer of hardwood, strongly tied to willow, poplar, cottonwood, elm, oak and other broadleaved trees. It shows a marked preference for wood that spends part of the year wet: driftwood, flood debris, exposed roots on eroding banks, submerged logs left dry by falling water. It also takes cut stumps and fallen trunks in open situations, and it seems to tolerate sun and drying far better than most gilled fungi.

The season runs from late spring through summer, sometimes into early autumn, making it one of the earlier gilled fungi of the year and further separating it from many autumn look-alikes.

Separating the Look-alikes on Structure

Neolentinus lepideus — the closest structural match, also with sawtoothed gills and a scaly cap, but larger and stouter, with broader flat brownish scales on a paler background, a distinct ring or ring zone on the stem, and a strong association with conifer wood, including worked timber such as sleepers and posts. It causes a brown rot, leaving cubically cracked wood.

Oyster mushrooms (Pleurotus species) — soft-fleshed, with smooth caps lacking dark scales, a lateral or absent stem, and smooth gill edges.

Panus species — tough and on hardwood, but with hairy or velvety caps lacking dark fibrillose scales, often with lilac tints when young, and smooth gill edges.

Lentinellus species — genuinely jagged gill edges, but the fruitbodies are shell- or fan-shaped with little or no stem, and the caps are unscaled.

Polyporus arcularius and P. brumalis — share the habitat, season, funnel shape and hairy margin, but the underside carries angular pores rather than gills.

Shaggy scalycap (Pholiota squarrosa) and relatives — clustered and conspicuously scaly, but the gills are attached rather than strongly decurrent, the flesh is soft, there is a ring, and the spore print is rusty brown.

A Working Checklist

1. Late spring to summer, on hardwood in an open or waterside setting.
2. Pale funnel-shaped cap with flat dark brown to blackish radial scales.
3. Decurrent, crowded, whitish gills with finely sawtoothed edges under a lens.
4. Tough pliant flesh that bends and shreds rather than snapping.
5. Central to slightly off-centre scaly stem, often clustered.
6. White spore print.