Zoned Tooth Identification Guide

Where and How You First See It

The Zoned Tooth turns up in old, unimproved woodland on poor ground: thin sandy or gravelly acid soil under beech and oak, mossy banks along woodland tracks, the raised lip of a ditch, the sparse litter under a stand of birch. The mycelium is long-lived, so productive sites are extraordinarily loyal and the same few square metres produce fruit bodies year after year for decades.

The first sighting is rarely a single neat mushroom. What you see is a low brownish crust or a rosette of overlapping flattened plates, sitting almost flush with the litter, with grass blades, twigs and conifer needles growing straight through it. That habit of caps fusing sideways into a compound sheet is written into the species name, and it is the first thing to note.

First Impression

Pick a piece up, or try to. It does not come away like a soft mushroom; it is tough, corky and fibrous, and it usually arrives with a lump of soil bound into the base. Turn it over and the underside is covered in short crowded spines rather than gills or pores. Look at the upper surface and you should see concentric bands of colour, ring within ring, with a paler zone at the edge. Tough, zoned, toothed and fused: those four words carry most of the identification.

The Cap Surface

Individual caps are 2 to 7 cm across, though fused groups can spread to 20 cm or more. A young fruit body begins as a small felted knob, expands to a flattened disc, and finally becomes centrally depressed and shallowly funnel-shaped.

Colour comes in concentric bands: alternating rings of cinnamon, reddish brown, purplish brown and near-black toward the centre, with the outermost band a pale cream, buff or faintly pinkish white where the cap is still actively growing. That white growing margin is a good sign of a fresh, readable specimen.

The surface texture is radially fibrillose and scurfy, and as the fruit body ages it develops radial ridges and wrinkles, and small raised tufts, scales or tubercles that concentrate toward the centre. Old centres go dark, roughened and often eroded. Where two caps meet they simply merge, engulfing any vegetation in the way, so a compound specimen may have a blade of grass emerging cleanly through the middle of a cap.

The Teeth

The spore-bearing surface is made of spines, which is the character that puts the species in the tooth fungi. They are crowded, 1 to 3 mm long, awl-shaped and tapering to a fine point, and they run decurrently down onto the stipe rather than stopping at its junction with the cap.

Colour changes with maturity and is worth reading carefully. Young spines are whitish to pale pinkish grey; as spores mature they darken through pinkish brown to purplish brown or dark brown, usually keeping paler tips. A specimen with dark purple-brown spines and pale points is at its most recognisable stage.

The Stipe and Base

The stipe is short and often barely distinguishable from the cap, roughly 1 to 3 cm long and 5 to 15 mm thick, frequently off-centre, and sometimes almost absent in strongly fused colonies. It is brown to reddish brown, felted or velvety, and it tapers or thickens slightly toward the base.

The base is normally matted with sand, soil, moss and litter bound firmly into the tissue, which is why clean extraction takes a knife and patience. Lift the whole base with the soil attached and clean it later; the shape of the base and the presence or absence of a spongy swelling are useful characters and easily destroyed by pulling.

Cutting It Open: Flesh, Zonation and Colour Change

Cut a fruit body vertically through cap and stipe. Expect resistance: the flesh is tough, corky and fibrous, more like a bracket than a gilled mushroom, and a blunt knife will tear rather than slice.

In section the flesh is thin and clearly two-layered in fresh material, with a softer felted upper layer over a firmer lower one, and it shows concentric and radial zoning in reddish brown and paler tones that mirrors the banding of the cap surface. There is no latex and no gelatinous layer. Handling and bruising darken the pale growing margin to brown, and old dried specimens harden, grey off and persist through the winter as recognisable but faded relics.

One chemical test is worth carrying. A drop of potassium hydroxide on the cut flesh turns it dark green to blue-black almost immediately, a reaction shared with related tooth fungi and useful for confirming that you are in the right genus rather than looking at an unrelated brown funnel-shaped fungus.

Taking a Spore Print

The print is brown, so use white paper. Spines are awkward because they shed onto a curved, uneven surface: cut the fruit body off at the base, lay it spines-down on white paper inside a covered box, and leave it overnight, ideally 12 hours or more, since these tough fungi release spores slowly. Choose a specimen with dark, fully coloured spines, because pale-spined juveniles may deposit almost nothing.

Under the microscope the spores are brown, subglobose to irregularly angular, and conspicuously ornamented with coarse tubercles or warts, around 5 to 6 micrometres excluding the ornament. A brown, warted spore is decisive against the white-spored tooth fungi.

Substrate, Partners and Season

This species is ectomycorrhizal, partnered chiefly with broadleaf trees, especially beech and oak, and also with birch, hornbeam and occasionally conifers. It favours nutrient-poor, well-drained, acidic ground with thin litter, which is why banks, track edges and eroded slopes are so productive and why rich, deeply mulched woodland floors are not.

Fruiting runs from midsummer through late autumn, with fruit bodies persisting long after they stop growing. They appear in troops, arcs and fused sheets rather than singly. Because the mycelium is slow-growing and intolerant of enrichment, populations are strongly tied to long-established, undisturbed woodland, and the genus is treated as a useful indicator of continuity in old woodland sites.

Separating the Look-alikes on Morphology Alone

• Hydnellum scrobiculatum is the closest match. Its cap is more strongly pitted and scrobiculate, with coarser radial ridging, its zoning is generally less crisp, and it tends to be more distinctly stalked and less prone to forming broad fused sheets. Many collections need careful comparison of the cap surface texture side by side.
• Hydnellum ferrugineum and spongiosipes have a thick, spongy, bulbous stipe and a felted pinkish-white cap that is not clearly banded, and young fruit bodies exude red droplets onto the surface.
• Hydnellum caeruleum shows blue tones in the young cap margin and blue zoning in the cut flesh.
• Phellodon tomentosus is the trap. It has a similarly zoned, funnel-shaped brown and tan cap, but its flesh is thin and leathery rather than corky, its spines stay whitish to pale grey rather than darkening to purple-brown, its spore print is white, and dried material develops a strong sweet aromatic odour. Print colour settles it every time.
• Phellodon melaleucus and confluens likewise combine dark caps with pale spines and a white print.
• Coltricia perennis mimics the zoned funnel-shaped cap and thin habit almost exactly, but its underside carries pores, not teeth, and it has a distinctly central stalk. Always look underneath before deciding.
• Hydnum repandum has spines but is soft, brittle and fleshy, pale cream to apricot, entirely unzoned, and drops a white print.
• Sarcodon species are much larger, with coarse raised scales, thicker flesh and no concentric banding.
• Thelephora terrestris forms fan-shaped brown rosettes on similar ground, but its underside is smooth to wrinkled with no spines at all.

Field Checklist

• Caps 2 to 7 cm, flattened to funnel-shaped, frequently fused into sheets.
• Upper surface concentrically banded in browns with a pale growing rim.
• Radial fibrils, ridges and small central scales.
• Spines crowded, 1 to 3 mm, decurrent, whitish then purplish brown.
• Stipe short, brown, felted, base matted with soil and litter.
• Flesh tough and corky, zoned in section, turning dark green-black with potassium hydroxide.
• Spore print brown; spores warted and subglobose.
• Poor acid soil under beech, oak and birch, midsummer to late autumn, faithful to the same site each year.