Ochre Spreading Tooth Identification Guide

First impression, and the setting

This is a species you find by turning things over. You are in damp deciduous woodland, or a hazel coppice, or along a shaded stream bank where fallen branches lie in the leaf litter, and you flip a dead stick that has been down for a year or two. On the underside, spreading along the wood in an irregular patch, is a soft crust the colour of tinned salmon or warm ochre, and its whole surface is bristling with tiny crowded spines.

The colour is the first thing that registers, because it is unusual on the woodland floor: a warm pinkish ochre to pale orange-brown when fresh and moist, quite unlike the whites and greys of most crust fungi. The second thing is the texture, which under a lens looks like the pile of a short brush or the surface of a coral.

Establishing the growth form

Before anything else, decide what kind of fruitbody you have.

Steccherinum ochraceum is primarily resupinate, meaning it grows flat against the substrate with the spore-bearing surface facing outward, like paint applied to the wood. Where the branch curves, however, the fungus frequently lifts the upper edge free and forms a narrow reflexed shelf, one to a few millimetres deep, sometimes up to a centimetre. This effuso-reflexed habit is very characteristic, and on a well-developed collection you will find both flat crust and small ledges on the same branch.

Where those small shelves exist, look at their upper surface: it is whitish to pale buff, finely hairy or felted, and often faintly zoned in concentric bands. That combination of a toothed underside with a small hairy zoned brim is a strong pointer.

Reading the spore-bearing surface

The spines carry the identification.

Look at them with a hand lens against a millimetre scale. They are conical to awl-shaped, mostly 1 to 3 mm long, straight or slightly curved, and crowded at roughly 3 to 5 per millimetre, which reads as densely packed but with visible individual points rather than a fused mass. On a vertical or steeply inclined branch face the spines often bend downward, following gravity.

Colour when fresh is the salmon to ochre already described, sometimes with a slightly deeper orange flush toward the older centre of the patch. As the fruitbody dries the colour retreats toward dull buff, pale tan or greyish ochre, and a dried herbarium specimen can be disappointingly drab. This means that colour, while diagnostic, must be judged on fresh, damp material.

Check that the teeth are genuinely free-standing spines. Press a fingertip gently and they should spring back rather than crumple as a sheet. In some superficially similar crusts what looks like teeth is really a pore layer or a wrinkled surface breaking up, and the difference is visible under a lens.

Reading the margin

The advancing edge is one of the most reliable characters and is frequently overlooked.

Around the perimeter of the patch, the fungus produces a narrow sterile zone that is paler than the toothed centre, white to cream, and distinctly fibrillose or cottony, breaking up into fine radiating strands and threads where it runs onto bare wood. Under a lens it looks fringed or feathery. That white fimbriate margin against a salmon-ochre toothed interior gives the species its recognisable two-tone look.

Old, weathered patches lose the margin, so young actively spreading material is much easier to name.

Reading the flesh in section

Slice down through the crust with a sharp blade, ideally at a spot where a small shelf has formed.

The tissue is thin, usually well under a millimetre in the resupinate parts, pale ochraceous to almost white, and tough rather than gelatinous. In the reflexed parts you can often make out two layers: a soft hairy upper tomentum and a firmer, denser layer beneath it, sometimes with a thin darker line between them.

There is no dramatic colour change on cutting or bruising. The crust does not redden, blacken or blue; the only shift you will notice is the gradual dulling as the specimen dries.

Under a microscope the confirming character is a set of thick-walled, heavily encrusted skeletal cystidia projecting among the spore-producing cells, with a crystal-covered apex. Together with small, smooth, ellipsoid spores around 3 to 4 by 2 to 2.5 micrometres and a hyphal system with clamps, this places the specimen firmly.

Taking a spore print

Resupinate fungi make prints awkward, but it can be done. Cut a small chip of branch bearing a fresh, actively growing patch and suspend it teeth-downward a few millimetres above a piece of dark glass or black card, propping it on matchsticks, then cover the whole arrangement to hold humidity. Left overnight in a cool place it will drop a faint white deposit.

Read that print carefully: it is white, and on white paper it is nearly invisible, which is why dark card matters. A white print excludes several brown-spored crusts outright. Do not be discouraged if a dry patch yields nothing; only fresh, moist, actively expanding material sporulates reliably.

Substrate and season

The substrate is dead hardwood, most often fallen or hanging attached branches of moderate diameter rather than large trunks. Hazel, ash, oak, beech, willow, sycamore, birch, elder and old fruit trees all support it, and it will also take to worked timber lying in damp shade. Conifer records exist but are much less usual.

Look on the underside and shaded flanks of the wood, where humidity stays high, and in situations where the branch is in contact with damp litter but not buried in it. Bark may still be present or the wood may be bare; the fungus colonises both.

Being a saprotroph, it causes a white rot, bleaching and softening the wood beneath into a pale fibrous condition. Fruitbodies can be found in any month, but they are at their best from autumn into mild winter periods, and after prolonged wet weather when colour and margin are freshest.

Separating it from close look-alikes

Irpex lacteus forms whitish to cream crusts with irpicoid teeth that are flattened, torn and often derived from broken-down pores rather than clean cones, and it lacks the salmon-ochre colour entirely.

Basidioradulum radula is cream to pale buff, with fewer, coarser, more widely spaced and often blunt or flattened warts and teeth, on a smooth waxy-looking base.

Radulomyces molaris produces coarse, thick, blunt teeth several millimetres long, well spaced, on a cream to pale ochre crust, and is strongly associated with oak.

Xylodon and Hyphodontia species are typically white to pale cream with shorter, finer teeth, no reflexed hairy brim, and no warm orange tones.

Phlebia radiata shares the warm orange to salmon palette but its surface is radially wrinkled, folded and waxy, not spiny, and its texture is gelatinous rather than tough.

Mucronella species produce separate individual hanging spines directly from the wood with no crust joining them at all.

Field checklist

Flat crust on the underside of a fallen hardwood branch; salmon to ochre when fresh; crowded conical spines 1 to 3 mm long at 3 to 5 per mm; white fibrillose fringed margin; occasional small hairy zoned reflexed brim; thin tough pale flesh with no colour change; white print. That is the ochre spreading tooth.