The passion fruit is not one plant but a great genus, and one of the most spectacular in the botanical world. Passiflora holds something over five hundred species, the overwhelming majority of them native to the tropical and subtropical Americas, and almost all of them vigorous climbing vines that haul themselves through the forest canopy on coiling tendrils. What they are famous for is the flower: an intricate, almost architectural bloom in which a ring of fine coloured filaments, the corona, radiates from the centre beneath a raised column bearing five anthers and three broad stigmas. It is a structure so unlike any European flower that the first missionaries to see it read it as a coded diagram of the Crucifixion, and gave the whole genus the name it still bears.

The fruit itself is a berry, and its architecture is as unusual as the flower's. Within a hard, hollow, leathery shell hang dozens of seeds, each wrapped in a translucent sac of intensely aromatic, sharply acidic juice called the aril; it is this pulp-and-seed mass, spooned straight from the halved shell or sieved for its juice, that is eaten. Nothing else in the fruit basket tastes quite like it, and the flavour is so concentrated and so high in acid that the fruit is very often used as a flavouring rather than eaten in quantity by itself.

Several species were taken into cultivation quite separately by different peoples of the Americas, and the kitchen still keeps them apart. The passion fruit of world commerce is Passiflora edulis, which exists in two distinct forms: the purple (f. edulis), a subtropical vine of southern Brazil, Paraguay, and northern Argentina, smaller, sweeter, and finer in perfume, and the yellow (f. flavicarpa), a vigorous tropical lowland form, larger, sharper, and far more productive, which is the workhorse of the juice industry. In the high Andes two further species were domesticated: Passiflora ligularis, the granadilla, whose brittle orange shell holds a sweet, mild pulp eaten fresh out of the hand, and Passiflora tarminiana and its close relative P. mollissima, the elongated yellow curuba of Colombia and tumbo or taxo of Peru and Bolivia. The lowlands of northern South America gave the enormous Passiflora quadrangularis, the giant granadilla or badea, whose thick flesh is treated almost as a vegetable. And far to the north, in the temperate woods and old fields of the south-eastern United States, grows Passiflora incarnata, the maypop, the one member of the family hardy enough to survive a frost, gathered by the peoples of the American South-East long before any European arrived.

For the whole of its early history the passion fruit stayed within the Americas, where it had been gathered and grown for centuries before Europeans arrived: the Tupi-Guarani peoples of Brazil cultivated the maracujá, the Andean peoples the granadilla and the tumbo, and the nations of the American South-East gathered the maypop. What the Europeans contributed at first was not transport but a name. Spanish and Portuguese missionaries in South America, struck by the extraordinary flower, read its parts as the instruments of the Passion of Christ, and in 1610 the Roman scholar Giacomo Bosio published in his great book on the Cross an interpretation drawn from drawings and descriptions sent home by friars in the New World. The flower became the flos passionis, and Linnaeus in due course made it Passiflora; the Jesuits used it as a teaching aid in evangelisation, a sermon growing on a vine.

The fruit's real travels began in the nineteenth century, carried by the botanical and colonial networks of the age rather than by the early conquistadors. Purple passion fruit reached Australia in the middle of the century and took to the warm, wet coastal strip of New South Wales and Queensland so completely that within a few generations a passionfruit vine on the back fence had become one of the fixtures of suburban Australian life, and its pulp the defining finish of the national dessert. From Australia the vine was carried on across the Pacific to Hawaii in 1880, where it naturalised, acquired the Hawaiian name lilikoʻi from the Maui gulch in which it was first planted, and entered the island kitchen so thoroughly that it is now one of the signature flavours of Hawaiian baking. Colonial planting carried it likewise into southern Africa, where South Africans took up the fruit under the Spanish-derived name granadilla, and onward up the continent to the highlands of Kenya and the Great Lakes, whose climate suits it perfectly and where fresh passion juice became an everyday drink. Dutch colonial horticulture carried it to the East Indies, and around Medan in northern Sumatra the markisa became a local speciality.

In the last half-century the passion fruit has completed its journey from curiosity to global commodity. Brazil, its homeland, remains overwhelmingly the largest grower and, unusually amongst tropical crops, consumes almost all of what it produces; Ecuador, Peru, and Colombia between them supply much of the world's juice concentrate, and Colombia exports the purple gulupa and the granadilla to Europe; Vietnam has risen very recently into the front rank of producers. And in the kitchens of the northern hemisphere, where the fruit will not grow, it has become one of the defining flavours of modern pastry: the sharp, perfumed acidity of passion fruit set against cream, white chocolate, or milk chocolate is one of the signature pairings of the contemporary European dessert.

The passion fruit today is above all a fruit of juice and of flavour rather than of the fruit bowl. Its pulp is so acidic and so intensely aromatic that comparatively little of the crop is eaten fresh; the great bulk is pressed, pasteurised, and concentrated for the juice, nectar, yoghurt, ice-cream, and confectionery trades, in which passion fruit is one of the most valuable of all tropical flavours. The yellow form of Passiflora edulis dominates that industry for its vigour and yield, whilst the sweeter purple form, and the Colombian gulupa, command the fresh export market.

Production is concentrated in the Americas and, increasingly, in Asia. Brazil is by a wide margin the largest producer on earth and, remarkably for a tropical crop, keeps almost the whole of its harvest at home, where suco de maracujá is one of the national drinks; Ecuador, Peru, and Colombia are the great suppliers of concentrate and of fresh fruit to Europe and North America; and Vietnam has expanded with extraordinary speed to become one of the leading growers. Beyond these, Kenya and the Great Lakes region, South Africa, Australia, Indonesia, Taiwan, and Sri Lanka all grow the fruit substantially, and the several Andean species (the granadilla, the curuba, and the tumbo) remain regional crops of real importance in their own countries even where they are unknown abroad.

The vine grows so readily wherever the climate allows that in much of tropical Asia it is now a commonplace of gardens and market stalls, and visitors often assume it must be native. Thailand raises it across the northern highlands, where it was promoted as a replacement crop for the opium poppy and is drunk as nam saowarot; southern India grows it through the Western Ghats, the Nilgiris, and the hills of Kerala and Tamil Nadu, whilst the north-eastern states, Mizoram above all, have made it a major commercial crop and a bottled squash; Vietnam, Taiwan, and Sri Lanka all grow it in quantity. Yet in these places the fruit is eaten overwhelmingly fresh, split and spooned straight from the shell, or else pressed into juice, squash, and cordial, and it has not, or not yet, given rise to a distinctive dish of its own. That is the pattern almost everywhere the passion fruit has arrived recently, and it says something about the fruit itself: its acidity is so high that it works most naturally as a flavouring and a drink rather than as the substance of a dish, and only a few kitchens have built real dishes upon it, namely those with a sweet, rich, dairy-heavy tradition standing ready to receive it. Brazil had its condensed milk, Australia its meringue, Venezuela its quesillo, and Hawaii its chiffon pie and its malasada; where no such tradition stood waiting, the passion fruit remains, however abundant on the vine, a fruit to be drunk and to be eaten as it is.

Around the fruit there has grown a body of regional cooking as distinctive as any in this atlas. It is the mousse de maracujá and the caipirinha de maracujá of Brazil; the sorbete de curuba of Colombia and the tumbo sour of Peru; the parchita quesillo of Venezuela; the maypop jelly of the American South, made from the only hardy member of the family; the passionfruit pavlova, the passionfruit butter, and the passionfruit sponge of Australia and New Zealand; the lilikoi chiffon pie and the lilikoi malasada of Hawaii; the granadilla fridge tart of South Africa; the fresh passion juice of Kenya; the sirup markisa of Sumatra; and, in the modern European pâtisserie, the passion fruit tart and the passion-and-chocolate pairing that has become one of the defining flavours of contemporary dessert. From a vine that European missionaries read as a sermon, the passion fruit has become one of the most recognisable flavours in the world.