Train Wrecker Identification Guide

The setting that names the fungus

Train Wrecker is one of the few larger gilled fungi you are more likely to meet on worked timber than in the woods. Old railway sleepers, telegraph poles, fence posts, pit props, decking boards, boardwalks, log piles and the cut faces of conifer stumps are all classic finds. The English name comes from its habit of rotting railway ties from the inside out. The first impression is of a stubborn, pale, hard mushroom shouldering its way out of a crack in a plank, often as a single fruit body or a small huddle, in a place where nothing else is fruiting at all.

It is worth registering the general shape before looking at details. This is a firmly built, dry mushroom with a whitish to buff cap dressed in flattened brown scales, a stem that is as tough as the cap, and gills that run down onto that stem. Nothing about it is soft, watery or fragile. Specimens can persist for weeks, going leathery and cracked but still recognisable.

Reading the cap

The cap is typically 5 to 15 cm across, occasionally larger, convex at first and then flat or shallowly depressed, sometimes irregular where the substrate has forced it into a corner. The ground colour is cream, whitish or pale buff, and over it lie concentric, flattened to slightly upturned scales in brown, tan or reddish brown, densest towards the centre and thinning towards the rim. The surface is dry and never viscid. The margin stays inrolled for a long while and is often ragged or shaggy.

In deep shade and constant damp, for example inside cellars, mine shafts or under a station platform, the fungus can grow in a distorted, antler like or coral like form with no proper cap at all. Such specimens are recognised by their substrate, their toughness and their gill fragments rather than by outline.

Gills, stipe and veil

Turn it over for the character that pins the genus. The gills are decurrent, running distinctly down the stem, moderately spaced, thick, whitish to cream ageing buff, and their edges are conspicuously jagged, torn or saw toothed. Run a fingertip along a gill edge and it feels notched. That combination of decurrent attachment, tough white flesh and serrate gill edges is the sawgill signature and separates the group at a glance from ordinary fleshy woodland mushrooms.

The stipe is 3 to 10 cm long and stout, central to somewhat eccentric, hard and almost woody, frequently tapering downwards where it plunges into a crack in the wood. Above there is often a fibrillose ring or an indistinct ring zone left by a partial veil; below that zone the stem is decorated with brown scales matching the cap, sometimes so dense that the base looks dark. The extreme base may be swollen or rooting into the timber.

Flesh and colour change

Cut a fruit body vertically. The flesh is white, thick and remarkably tough, corky to fibrous, and resists a blunt knife. It does not change dramatically on cutting, although older material may dull to cream or take on a faint yellowish or pinkish cast with age and drying. Dried specimens shrink to something like hard leather and can swell again in rain. Many collections give off a pleasantly aromatic, aniseed like or resinous smell, especially fresh from softwood.

This toughness has an anatomical basis: the flesh contains skeletal binding hyphae of the kind normally associated with bracket fungi rather than the soft flesh of typical gilled mushrooms. It is a genuine field clue, not just an impression.

Taking and reading the spore print

Because the cap is tough and slow to release, allow more time than usual. Cut the cap free of the stem, place it gill side down on white paper or, better, half on white and half on dark card, cover it with a bowl and leave it eight to twelve hours in a cool place. The deposit is white to very pale cream and is easiest to see against the dark half.

Under the microscope the spores are smooth, hyaline and cylindrical to narrowly ellipsoid, and they do not stain blue grey in iodine. That last point matters, because the cockleshell fungi, Lentinellus, look superficially similar with their torn gill edges but have small, rounded, finely spiny spores that do react in iodine.

Substrate, decay type and season

This is a brown rot fungus of conifer wood: pine above all, also spruce and larch. It thrives on timber that has been seasoned, sawn, and often treated or creosoted, which is why it turns up on structures rather than in natural forest as often as not. The wood it leaves behind becomes brown, dry and cracked into cubes. Hardwood collections are unusual. The season runs from late spring through summer into autumn, earlier than most woodland gilled fungi, and single fruit bodies can persist for a month or more.

Separating the closest look-alikes

Lentinus tigrinus shares the pale cap with darker scales and the toothed decurrent gills, but it is smaller and thinner fleshed, its scales are finer, darker and more bristly, and it grows on hardwood, characteristically on willow and poplar in damp riverside places, in spring and early summer rather than on conifer timber.

Neolentinus adhaerens grows on conifer too but is smaller, has a resinous, sticky cap and typically exudes amber droplets on the gill edges and flesh, and its gill edges are less obviously sawn.

Heliocybe sulcata is a small, sun baked relative of exposed dead conifer wood with a strongly radially grooved and cracked cap and a short stem, quite unlike the broad scaly disc of Train Wrecker.

Shaggy Scalycap, Pholiota squarrosa, has an equally scaly cap but grows in dense clusters at the base of living hardwoods, has adnate to slightly decurrent gills that turn rusty brown, softer flesh, and drops a rust brown rather than white print.

Honey fungus, Armillaria species, can occur on conifer stumps with a scaly cap and a ring, but the gills are only shortly decurrent with even, uncut edges, the flesh is comparatively soft, and the fruit bodies grow in large tufts with black rhizomorphs under the bark.

Finally, Dryad's Saddle and other scaly polypores share the pattern of dark scales on a buff cap but have pores rather than gills beneath, which resolves the question in one glance.