English truffle (Tuber aestivum).—S.C. Porter/Bruce Coleman Inc.
Edible underground fungus in the genus Tuber (order Pezizales, phylum Ascomycota) that has been prized as a food delicacy since antiquity. Native mainly to temperate regions, truffles flourish in open woodlands on calcium-rich soil. The different species range from pea-sized to orange-sized. Truffles usually are associated with tree roots and are found up to about 1 ft (30 cm) below the soil surface. Experienced gatherers occasionally detect mature truffles by scent or by the morning and evening presence of hovering columns of small yellow flies but more often with the help of trained pigs or dogs. The truffle is important in French cookery, and truffle gathering is an important industry in France. Truffles are among the most highly valued foods in the world. False truffles (genus Rhizopogon, order Boletales, phylum Basidiomycota) form small, underground, potato-like structures under coniferous trees in parts of North America.