Glazed Cup Identification Guide

First impressions

Glazed Cup is a small object that rewards slow walking. You are usually in damp deciduous woodland, on a shaded bank, along the compacted edge of a track, or on bare soil where a root plate has torn up or a stream has left a silt shelf. Moss is often nearby, and there is frequently buried or half-rotted wood in the ground beneath.

What you see is a cup, one to three centimetres across, sitting directly on the soil without any stalk. From above the inside is startlingly pale - chalky white, ivory, or faintly greyish - and it looks smooth and slightly glassy, which is where the name comes from. From the side the picture changes completely: the outside is brown and shaggy, densely coated in stiff hairs, and the rim is edged with a ragged fringe of the same hairs standing proud of the margin. That contrast between a pale polished interior and a coarse brown exterior is the whole identification in one glance.

This is an ascomycete, not a gilled fungus, so the entire inner surface of the bowl is the spore-producing layer. There is no cap, no gills and no stem to work through, and the identification instead runs through shape, hairs, margin and spores.

Reading the inner surface

Start with the hymenium, the concave inner face. In fresh material it is whitish to very pale grey, sometimes with the faintest bluish or lilac cast in shade, and it dries to a duller cream. It should look even and slightly waxy, not wrinkled or veined. Ageing cups yellow slightly and the surface can become a little uneven, but it never turns the warm brown of a Peziza.

Check depth. Glazed Cup is genuinely deep - close to a hemisphere, sometimes deeper than a half sphere, with the margin curving inwards rather than flaring out. Shallow saucers and flat discs belong elsewhere. The depth stays visible even in older material because the cup does not usually expand flat.

The outer surface and the hairs

Roll a specimen carefully onto its side with a knife blade. The outside is covered from base to rim in a dense felt of stiff, straight, dark brown hairs. Under a hand lens they are thick-walled, pointed, and clearly separate rather than matted into wool. They are longest and most conspicuous at the rim, where they project past the edge to give the characteristic bristly fringe, and this fringe frequently traps soil grains and litter fragments.

Run a lens along the rim itself. In good material the margin looks toothed or eyelashed, but the hairs are brown, not black, and they are relatively short and stout rather than long and whippy. The base of the cup is often slightly pinched where it meets the substrate, with hairs and fine brown threads binding it to soil particles.

Flesh, substrate contact and how it grows

The flesh is thin, brittle, and pale; a cup snaps rather than tears. There is no colour change on cutting and no latex. Lift several and note how they grow - typically scattered to gregarious in small groups rather than in dense fused clusters, each one anchored individually. Very often you will find that the anchoring point involves a buried twig, a chip of decaying wood or a mass of rootlets rather than pure mineral soil, so it pays to sift the top centimetre with a fingertip and record what is actually there.

Getting spores from a cup fungus

You cannot take a spore print the usual way from a cup, because the spores are shot upwards out of the asci rather than dropped. Two techniques work in practice.

The simplest is the puff test. Bring a fresh cup into still air, let it warm slightly in your hand, then breathe gently across the open face. A synchronised discharge often produces a visible white smoke of spores rising a centimetre or two above the bowl. That alone confirms you are dealing with an operculate ascomycete.

For a deposit, invert the cup a few millimetres above a glass slide or dark card inside a closed box and leave it for a few hours; the discharged spores settle as a faint whitish film. Examined with a microscope the spores are large and distinctive: broadly elliptical, roughly 20-27 x 10-14 micrometres, ornamented with coarse warts, and each typically containing two large oil drops. The asci are eight-spored and open by a lid. That combination of very large warty two-guttulate spores plus brown pointed hairs is decisive.

Substrate and season

Glazed Cup is a saprotroph of soil and buried wood. It favours damp, shaded, often disturbed ground: bank sides, ditch edges, path cuttings, root pits, mossy woodland floors and the soil around decaying stumps. It shows a preference for broadleaved woodland but turns up under conifers and in gardens too, and it is not restricted to a particular soil chemistry, though heavier and richer soils seem to suit it. Fruiting runs from early summer through to late autumn, later than most spring cup fungi, and it is often at its best after a warm wet spell in mid summer when the surrounding woodland has little else to show.

Separating the look-alikes on structure alone

• Scutellinia species (eyelash cups) have a bright orange to scarlet inner disc and very long, jet-black, tapering marginal hairs. Colour and hair length separate them instantly; Glazed Cup is never orange inside.
• Trichophaea species are smaller, much shallower - often almost flat discs - and clothed in longer, paler, more spreading brown hairs. Their spores are smooth and lack the coarse warts.
• Tarzetta cupularis and Tarzetta catinus are also deep cups on soil, but their outer surface is finely granular or scurfy rather than bristly, the margin is toothed but hairless, and the exterior is buff to pale ochre rather than dark brown.
• Geopora species develop mostly buried in soil and split open at the top into star-like lobes; their hairs are brown but the fruitbody shape and the way it erupts from below are quite different.
• Peziza species are usually larger, brown or ochre on the inner face, and have a smooth or minutely scurfy outside with no hair coat at all.
• Cheilymenia species occur on dung, are yellow to orange inside, and have conspicuous hairs; substrate plus colour separates them.

Field checklist

Deep hemispherical stalkless cup one to three centimetres wide; pale whitish glazed inner face; dense stiff dark brown hairs outside; a bristly fringe standing above the rim; on damp shaded soil or buried wood; summer to autumn; very large coarsely warted spores with two oil drops. That set belongs to Glazed Cup and to nothing else you are likely to meet.