More than almost any other seasoning, 'bay leaf' is a name worn by several quite unrelated plants, bound together by nothing more than a broadly similar habit of use: a tough, aromatic, evergreen leaf, dropped whole into the simmering pot to lend its fragrance and lifted out before serving. The original and the true bay is the bay laurel, Laurus nobilis, an evergreen tree of the Mediterranean and Asia Minor and a member of the Lauraceae, the laurel family that also gives the world cinnamon, the avocado, and sassafras. Its dark, glossy, leathery leaf carries a warm, faintly bitter, eucalyptus-and-clove fragrance from the compound eugenol and others, and it is the bay of European, Mediterranean, and Latin American cooking, the silent backbone of the stock, the stew, and the marinade.

Three other 'bays' matter greatly at the table, and not one is a close relative. The Indian bay leaf, tejpat (Cinnamomum tamala), is a cousin of cinnamon rather than of the laurel: a long, three-veined leaf from the Himalaya whose scent is frankly that of cinnamon and clove, nothing like the Mediterranean leaf for which it is so often, and so wrongly, substituted. The Indonesian bay, daun salam (Syzygium polyanthum), belongs to a third family altogether, the Myrtaceae of the clove and the allspice, and lends a gentle, sour, herbal note to the cooking of the Malay archipelago. The Mexican bay (Litsea glaucescens) is, like the true laurel, a member of the Lauraceae, and is the 'laurel' of the Mexican kitchen. Two further plants borrow the name without earning a regular place in the pot: the pungent California bay (Umbellularia californica), the so-called headache tree, used sparingly as a stronger stand-in, and the West Indian bay (Pimenta racemosa), a clove relative grown chiefly for bay rum. It is worth a word of caution that the cherry laurel and other ornamental 'laurels' are not culinary at all and are poisonous; only the true bay laurel and its named culinary namesakes belong in food.

The true bay laurel was sacred long before it was culinary. To the Greeks it was the tree of Apollo, sprung from the nymph Daphne who was changed into a laurel to escape the god, and its leaves crowned the victors of the Pythian Games, wreathed the brows of poets, and were chewed, so it was said, by the Pythia, the priestess of the Delphic oracle, to bring on her prophetic trance. Rome took the laurel as the emblem of triumph and victory, crowning its generals and emperors with it, and as the legions marched the tree went with them, planted across Gaul, Iberia, and Britannia, so that the Mediterranean laurel struck root throughout the European provinces. From this Roman diffusion the leaf passed quietly into the kitchen of medieval and Renaissance Europe and became indispensable: the heart of the French bouquet garni and court-bouillon, the perfume of the stock pot, the stew, and the milk pudding from Italy to England.

With the age of sail the laurel crossed the oceans. The Spanish and Portuguese carried it to the Americas, where 'laurel' became a fixture of the Hispanic kitchen, scenting the sofrito, the black beans, and the adobo of the Caribbean and Latin America; and across the Pacific the Manila galleon carried it to the Philippines, where the bay leaf lodged at the very centre of adobo, the national dish. Meanwhile, on the far side of the world and quite independently, the other bays kept to their own homelands: tejpat had long flavoured the Mughlai and North Indian kitchen; daun salam was woven through the cooking of Java, Sumatra, and the Malay world; and the Mexican laurel seasoned the caldos and adobos of Mesoamerica. Four leaves, four families, four corners of the earth, gathered under a single borrowed name.

The Mediterranean bay is the great anonymous workhorse of the Western kitchen, so quietly pervasive that its absence is felt more than its presence. It goes into almost every stock, court-bouillon, and bouquet garni; into the long braises and daubes of France, the ragùs and braised meats of Italy, the bean pots and lentil stews of Spain and Portugal, and the escabeche and adobo of the whole Hispanic world. The British and French infuse it into milk for béchamel, bread sauce, rice pudding, and custard; the cooks of Latin America drop it into the sofrito and the frijoles; and it perfumes pickles, marinades, and the American pickling spice and crab boil. It is rarely tasted on its own and almost never the dominant note, yet it rounds, deepens, and binds the flavours around it.

The other bays hold their own regional thrones. In northern India tejpat, the Indian bay leaf, is one of the whole spices dropped into hot fat at the start of a biryani, a pulao, a dal, or a Mughlai curry, and a classic component of garam masala, lending its cinnamon-clove warmth. In Indonesia and the Malay world, daun salam is as fundamental as the Mediterranean bay is in Europe, scenting the coconut rice, the gulai, the sayur, and the sambal goreng of the everyday table. In Mexico, the native laurel seasons the caldo, the adobo, the pot of frijoles, and the long-simmered mole. Each is, in its own cuisine, the indispensable aromatic leaf; and though a European cook and an Indian and an Indonesian would scarcely recognise one another's 'bay', each would be lost without their own.