Lemon Peel Fungus Identification Guide

First impression

The Lemon Peel Fungus is one of the more theatrical woodland cup fungi, and it usually announces itself as a small cluster of upright, ear-shaped structures pushing through leaf litter on a shaded bank. Each one stands 3 to 10 cm tall and looks as though a rounded cup had been slit from the rim almost to the base on one side and then allowed to lean and curl. The taller side rises and folds inward; the shorter side drops away.

The colour is the second hook: a warm ochre-yellow to apricot, and, on the inner face, a distinct rosy or salmon-pink flush that is strongest across the middle of the cup. Once you have seen that pink wash over yellow you will recognise it instantly, though it fades on old and sun-bleached material.

The setting

Expect damp deciduous woodland on neutral to calcareous soil, most often under beech and oak, sometimes with hazel, hornbeam or lime. Typical microsites are mossy banks, the shaded margins of woodland paths, hollows where leaf litter accumulates, and the sheltered ground beneath dense canopy. The fungus grows from soil and buried litter, not from exposed wood.

The season runs from late summer through autumn. Fruit bodies almost always appear in small tufts, with several individuals fused at a common pale base, and colonies tend to recur in the same spot in successive years.

Reading the cup

Work through the structure deliberately; the shape carries more information here than any single colour.

Overall form. A deep, markedly asymmetric cup, 2 to 5 cm wide and taller than it is broad, split down one side from the rim to near the base. It is never a symmetrical bowl. The split is a defining structural feature, not accidental damage, and it is present on every mature specimen.

Rim. Wavy, often irregularly notched or shallowly toothed, and frequently rolled slightly inwards on the tall side. On old specimens the rim can split further into two or three lobes.

Inner surface. This is the hymenium. It is smooth, matte and even, ochre-yellow to apricot, overlaid with the characteristic pinkish to rosy-salmon flush. Tilt the cup in different light before judging the colour; the flush is easiest to see when the surface is not glaring.

Outer surface. Paler and more consistently yellow-ochre to buff, without the pink. Under a lens it is finely mealy or minutely granular, with a slightly powdery look, and it is not hairy or velvety.

Base, stem and how to lift it

Do not pull the fruit body straight up. Cut around it with a knife and lift the whole base out with the surrounding litter, because the base is diagnostic.

Below the cup, the tissue narrows into a short, whitish, stem-like column, usually 1 to 2 cm long and largely buried. It is clothed in white mycelial felt that binds soil, moss fragments and leaf debris, and in a tuft several cups arise from a shared mass of this white tissue. That white basal felt, joining several fruit bodies, is a useful confirmation of the species-level cluster habit.

Flesh and colour change

The flesh is thin, only 1 to 2 mm, pale cream to buff, and brittle in a waxy way. Bend a section and it snaps cleanly rather than tearing along fibres. There is no latex of any kind, and cut surfaces do not change colour on standing: no bluing, no reddening, no browning beyond ordinary drying. Record that absence of reaction, since it helps eliminate several unrelated cups.

Getting a spore deposit

This is an ascomycete, so the spores are discharged actively from the inner surface. Cut a mature cup free, rest it hymenium-down a few millimetres above dark card inside a closed box with a little moisture, and leave it several hours to overnight. The deposit is white.

In the field, a mature cluster will often release a visible puff of spores if you breathe gently on it or knock it after a change in humidity. That is a quick way to confirm maturity before bothering with a deposit.

Under a microscope the spores are smooth, ellipsoid and hyaline, each containing two conspicuous oil drops, and the asci contain eight spores and do not turn blue in iodine. The combination of smooth two-guttulate spores and an eight-spored inamyloid ascus is consistent across the genus.

Habitat and season as evidence

Otidea species are generally understood to be ectomycorrhizal or at least closely root-associated, which is why they appear in the same shaded woodland spots year after year rather than on decaying wood or in the open. If you find a split ear-shaped cup in a lawn, on a bonfire site, or growing directly out of a log, look elsewhere in the key.

Separating it from the look-alikes on morphology

Otidea leporina is the closest structural match: same split ear form, similar size. It is browner and more tan-ochre throughout, lacks the rosy flush on the inner face, tends to be narrower and more sharply pointed, and is more often associated with conifers. Colour, not shape, separates them.

Otidea alutacea is duller, greyish-tan to olive-brown, larger and more open, with the split less deeply developed so the cup approaches a lopsided bowl rather than a true ear.

Otidea bufonia is a dark chocolate to blackish-brown species; no yellow, no pink.

Otidea concinna is a clean chrome-yellow with no pink flush at all and is generally shorter and more open.

Peziza species form regular, symmetrical, sessile bowls that are not split down one side, are usually brown or lilac-brown, have thicker and more watery flesh, and often grow on soil, burnt ground, mulch or rotten wood.

Aleuria aurantia is bright orange, forms flat saucers rather than tall ears, may crack irregularly with age but never opens as a single clean lateral slit, and has a whitish downy outer surface. It also favours bare disturbed soil and path edges rather than deep litter.

Helvella species with cup-like forms sit on a distinctly ribbed or fluted stem, and their tissue is tougher and greyer.

A working field sequence

1. Confirm the habitat: shaded deciduous woodland, leaf litter, often on lime-rich soil.
2. Confirm the form: a tall, one-sided cup split from rim to near the base.
3. Judge the inner surface for the apricot ground plus rosy-pink flush.
4. Check the outer surface: paler, finely mealy, not hairy.
5. Excavate the base and look for a short white stem-like column with mycelial felt.
6. Snap the flesh; expect brittle, thin, unchanging tissue.
7. Take a deposit in a humid box and expect white.