Never eat a wild mushroom identified only from a website, a book or an app. Have every find checked in person by an expert, such as a mycological society.
Identification
The summer truffle is an underground, rounded to irregular fruit body 2–10 cm across, with a black skin covered in large, pyramid-shaped warts. The flesh is firm, pale cream to light brown in summer specimens and darker hazel to chocolate brown in autumn ones, marbled with white veins. The aroma is pleasant but milder than that of the Périgord truffle, often described as nutty or like hazelnut and mushrooms. Under the microscope the spores are brown and ellipsoid with a distinctive honeycomb-like network on their surface.
Tuber uncinatum, the Burgundy truffle, was described as a separate species, but genetic studies show it is the same species as T. aestivum; the difference lies mainly in season and ripeness.
Habitat and ecology
Tuber aestivum is ectomycorrhizal with many trees, including oaks, hazel, beech, hornbeam, lime and pines. It grows on calcareous, well-drained soils from the Mediterranean to central and northern Europe, including Germany, Switzerland, the United Kingdom, Scandinavia and eastern Europe. It tolerates cooler climates than the black winter truffle, which explains its wide range. Fruit bodies form a few centimetres below the surface and are located by trained dogs.
Uses and importance
Summer truffle is used generously compared with winter truffles: shaved raw over pasta, eggs, salads, carpaccio and risotto, or infused in butter or oil. Its aroma is fragile and weakens with long cooking or storage, so it is best used fresh within a few days. Autumn Burgundy truffles have a stronger aroma and fetch higher prices than summer harvests. As with all truffles, many "truffle-flavoured" products contain synthetic aroma rather than real truffle.
Cultivation
Tuber aestivum is cultivated in truffle orchards much like the black truffle. Oak, hazel or hornbeam seedlings inoculated with the fungus are planted on calcareous, well-drained soils with good structure. Because it tolerates cooler climates, it is grown in central Europe, including Germany and Switzerland, as well as in the Mediterranean. Harvests begin after several years and remain variable; soil analysis and suitable site selection are essential before planting.
Safety and edibility
The summer truffle is a safe edible. Risks lie mainly in confusion with toxic underground or ground-level fungi and in fraud. If you find truffle-like fungi yourself, identification must be confirmed in person by an expert, such as a mycological society or truffle specialist. Earthballs (Scleroderma citrinum and relatives) are toxic and can look like truffles from the outside; Choiromyces meandriformis is considered toxic or indigestible. Wild truffle harvesting is regulated or protected in many countries; check local rules before searching.
If you suspect mushroom poisoning, call your local emergency number or poison centre straight away, even before any symptoms appear, and keep the remains of the mushrooms.
Look-alikes
The Périgord black truffle (Tuber melanosporum) has small flat warts and purplish-black flesh in winter. Tuber mesentericum (Bagnoli truffle) looks similar but has a phenolic, tar-like smell. Tuber brumale has dark flesh with broad white veins and finer warts. Scleroderma citrinum (common earthball) has a hard, yellowish, scaly skin, grows at ground level and has purplish-black flesh without white veins; it is toxic. Spore microscopy separates these species reliably.
Around the world
The summer truffle has the widest distribution of all commercially used truffles, from North Africa and the Mediterranean to Scandinavia and eastern Europe. It is the main truffle traded in summer and autumn and an increasingly important crop for truffle growers in cooler regions.
