Lemon Peel Fungus

The Lemon Peel Fungus is the most colourful member of Otidea, a genus of ear-shaped ascomycetes in the family Pyronemataceae. Rather than forming a symmetrical bowl, the fruiting body is split from margin to base down one side and grows taller on the opposite side, producing an asymmetric structure that looks convincingly like an animal's ear or a curled strip of citrus peel.

Colour is what separates it from its relatives: the outside is a clean ochre-yellow to yellow-tan, while the inner, spore-bearing surface carries a distinct apricot, salmon or pinkish flush over the yellow ground. That warm pink tone is present in fresh material and is the character most guides key on.

Fruiting bodies usually appear in small clusters, several arising from a common point in the litter and leaning outward like a group of ears. They are firm and slightly rubbery rather than brittle, a texture typical of the genus.

Fruiting body

Ear-shaped, 3–10 cm tall and 2–5 cm wide, split down one side from the margin all the way to the base, with one side elongated and often incurved so that the whole structure leans. The margin is usually entire and slightly inrolled.

Surfaces

The outer surface is ochre-yellow to yellow-brown and finely mealy or minutely scurfy. The inner surface is smooth and yellow with a clear apricot, salmon or pinkish-flesh flush, strongest in fresh specimens and fading with age and drying.

Stipe

The base narrows into a short, stalk-like point of attachment, typically whitish and clothed in fine white mycelial down where it enters the litter.

Flesh & spore print

The flesh is thin, pale yellowish, firm and slightly pliant, with no latex and no colour change when cut. The spore print is white; the spores are smooth and elliptical, usually with two conspicuous oil droplets.

This species grows on soil, humus and leaf litter in deciduous and mixed woodland, with a strong preference for beech and oak, and it also occurs under other broadleaved trees and occasionally in mixed stands with conifers. It favours mossy, shaded, moist ground and is often found in small tufts rather than singly.

Fruiting runs from late summer into autumn, peaking in the main autumn mushroom season. The species is widespread across temperate Europe and occurs across much of temperate North America, though it is generally scattered rather than abundant.

Otidea species are ground-dwelling fungi of forest litter, and the genus is generally regarded as saprophytic on humus and leaf litter, with some evidence suggesting a degree of association with tree roots. Whatever the precise relationship, the mycelium spreads through the upper humus layer beneath broadleaved trees and the fruiting bodies emerge directly from that layer.

The split, ear-shaped form means the spore-bearing surface is held vertically rather than facing the sky. Spores fired from the asci travel horizontally into the moving air of the litter layer, which suits a fungus fruiting among leaves and moss where an upward-facing cup would quickly fill with debris.

Hare's Ear (Otidea leporina) is the same shape but lacks the pinkish flush, being a fairly uniform tan to yellow-brown or fox-brown inside and out, and is more often found under conifers. Tan Ear (Otidea alutacea) is duller leather-brown to greyish tan, opens into a broader, more cup-like shape, and is less strongly ear-like. Toad's Ear (Otidea bufonia) is much darker, dark brown to blackish brown, and more robust.

Wynnea species form larger, clustered rabbit-ear structures rising from a common tuberous base and are much darker reddish brown. Split Peziza cups can superficially resemble an ear, but they are brittle rather than pliant, split irregularly by expansion rather than growing asymmetrically from the start, and are usually browner.