Scleroderma citrinum

Scleroderma citrinum, the common earthball or pigskin poison puffball, is a poisonous, puffball-like fungus recognised by its tough, scaly, yellow-brown rind and firm flesh that turns purplish-black as its spores ripen. The ball-shaped fruiting body, usually 2.5-7.5 cm across, sits directly on the ground without a stem and is ectomycorrhizal, forming root partnerships with oaks, beeches, birches and conifers. It is common in woods and on heaths across the north temperate zone. Despite its superficial resemblance to edible puffballs, S. citrinum is toxic and must not be eaten.

History

The common earthball was described by the mycologist Christian Hendrik Persoon in 1801, in his Synopsis Methodica Fungorum. The genus name Scleroderma comes from the Greek skleros ("hard") and derma ("skin"), describing the tough outer rind, while the epithet citrinum means "lemon-yellow". For much of the twentieth century it was widely catalogued under the synonym S. aurantium. It has never been a food or medicinal staple because of its toxicity, though it has occasionally been used in central Europe - improperly - to adulterate truffle products, a practice strongly discouraged given its poisonous nature.

Overview

Ecologically, Scleroderma citrinum is an important mycorrhizal partner, exchanging soil nutrients with its host trees, and it is itself frequently parasitised by the bolete Pseudoboletus (Boletus) parasiticus, which fruits directly on its surface. It is not cultivated and has no culinary value. The most important practical fact about this species is its toxicity: it is regularly confused with edible puffballs and, in its young button form, can be mistaken for deadly Amanita species. Key separating features are the thick warty rind, the firm flesh that matures to a marbled purplish-black, and the absence of a true stem. Cutting any puffball in half to check for a uniformly white interior is the single most reliable safeguard against poisoning.