The blackberry, like its cousin the raspberry, is not one plant but a whole tribe of closely related brambles, and it is amongst the last of the common fruits to have been brought under the discipline of the orchard. Botanically it belongs to the genus Rubus, and specifically to the subgenus Rubus (long called Eubatus), the section that holds the true blackberries and the trailing dewberries; it is separated from the raspberries of the subgenus Idaeobatus by one decisive and easily seen difference. When a ripe raspberry is pulled from the plant it slips free of its pale central core and comes away as a hollow thimble; the blackberry, by contrast, keeps its core, so that the picked fruit is solid, carrying away the white fleshy receptacle at its heart. Both fruits are aggregates, not true berries: each is a cluster of tiny drupelets, every drupelet a miniature stone fruit with its own pip, massed together on the receptacle.

The blackberry's taxonomy is notoriously the despair of botanists, for the European bramble reproduces very largely by apomixis, setting seed without true fertilisation, so that each self-perpetuating line breeds true and can be described as a distinct 'microspecies'. Several hundred of these have been named across Europe, and the whole assemblage is gathered under the convenient collective label Rubus fruticosus aggregate; the study of them has its own name, batology. What all of them share is the character of the wayside and the woodland edge: a vigorous, thorny, arching cane that roots wherever its tip touches the ground, colonising hedgerow, clearing, railway bank, and abandoned field with a speed and a tenacity that have made the bramble both a beloved wild larder and a formidable weed.

Unlike the apple or the grape, the blackberry was scarcely cultivated at all for the whole of its history. It grew so freely and so abundantly in the wild, and its thorns made it so unwelcome a garden guest, that there was little reason to plant what the hedgerow gave away; the fruit was gathered, not grown, from the Palaeolithic until deep into the nineteenth century. Serious domestication is therefore very recent, and it happened above all in North America, where nurserymen from the eighteen-forties onward selected thornless and heavy-cropping forms from the wild upright blackberries of the east and the trailing brambles of the Pacific coast. From that late and largely American work came the great modern novelty of the blackberry's story: the deliberate crossing of blackberry with raspberry to make wholly new fruits, the loganberry, the boysenberry, and the marionberry amongst them, a family of hybrid berries that exists nowhere in the wild and belongs entirely to the modern kitchen garden.

For almost the whole of its history the blackberry did not travel, because it did not need to: the bramble grew wild across the length and breadth of the temperate Northern Hemisphere, and each region gathered the fruit that grew at its own door. The peoples of Neolithic Europe ate it in quantity, and the evidence is unusually intimate; blackberry pips have been recovered from the stomachs of Iron Age bog bodies, and the fruit turns up in settlement layers from the Stone Age onward. The classical world knew the bramble as a plant of medicine before one of pleasure: the Greeks called it batos, and the physician Dioscorides prescribed its leaves and its unripe fruit as an astringent against fluxes and sore throats, a use that ran on unbroken through Gerard and Culpeper to the folk medicine of the nineteenth century. The Latin poets and agriculturalists knew it as rubus, the bramble of the neglected field and the tomb, and the fruit itself was morum, a word Latin used indifferently for the blackberry and the mulberry, a confusion that would be written permanently into the Romance languages.

Because the bramble was everywhere, its 'voyage' was really a scattering of separate wild inheritances that met only in the modern age. In Britain the blackberry became, and remains, the archetypal wild fruit, the free harvest of the September hedgerow gathered by everyone from the cottager to the crown, and hedged about with a rich folklore that fixed the end of the picking season by the calendar and the Devil alike. Across the Atlantic the woodland nations of North America gathered their own upright blackberries and trailing dewberries, drying them for winter and cooking them into the settler kitchen that would follow; and on the Pacific coast grew the trailing Rubus ursinus, the native dewberry that would prove the mother of the modern hybrid berries. In the South Caucasus and northern Iran grew yet another, the vigorous Rubus armeniacus, which under the misleading nursery name of the 'Himalayan Giant' would be carried to the Pacific Northwest and, escaping cultivation, become at once the dominant wild blackberry of the American west and the backbone of its processing industry.

The true travels of the blackberry are thus a modern and largely deliberate affair. The Californian hybridists of the eighteen-eighties, James Harvey Logan foremost amongst them, crossed the native trailing blackberry with the red raspberry to make the loganberry, and their successors made the boysenberry after it; these new fruits were then carried out to the temperate colonies of the southern hemisphere, above all to New Zealand, which took to the boysenberry so completely that it became the largest producer of that berry on earth. The European bramble travelled too, following European settlers to the cool south, where in the German-founded farming country of southern Chile it naturalised into an abundant wild crop that filled the mermelada pot and the kuchen tin. And in the last decades of the twentieth century the blackberry became, at last, a fruit of world commerce, as the highland valleys of Michoacán in Mexico turned the zarzamora into a vast fresh export that now keeps blackberries on the shelves of Europe and North America through the whole of the northern winter.

The blackberry today leads a double life much like the raspberry's. On one side stands the wild bramble, still gathered free from the hedgerow and the woodland edge across Britain, Europe, and North America, the very emblem of the foraged fruit and of late summer; on the other stands a young but fast-growing commercial crop, transformed within a single lifetime from a fruit too thorny and too perishable to bother with into one of the fashionable soft fruits of the modern shelf. The rise of thornless, upright, heavy-cropping cultivars and, above all, of long-keeping export varieties has turned the blackberry from a fleeting local treat into a fruit available the year round.

Several distinct kinds share the modern trade, and the kitchen still tells them apart. The wild European bramble (Rubus fruticosus aggregate) remains the fruit of the British and European hedgerow and of the jelly pan. The upright blackberries of North America, descended from Rubus allegheniensis and its kin and much improved by American breeders, are the mainstay of the fresh-fruit punnet. The trailing brambles of the Pacific coast, bred from the native Rubus ursinus, gave rise both to the marionberry, the intense, aromatic processing berry that made Oregon the heart of the North American crop, and to the great hybrid berries, the loganberry and the boysenberry, in which blackberry and raspberry are combined. The Armenian blackberry (Rubus armeniacus), naturalised across the American west, supplies much of the fruit that is frozen and pulped for jam, juice, and the confectionery trade.

Production now spans both hemispheres and every season. Mexico, and above all the state of Michoacán around the town of Los Reyes, has become the world's greatest exporter of fresh blackberries, its harvest flowing north through the winter; the Pacific Northwest of the United States remains the centre of the processed crop and the home of the marionberry; New Zealand is the world's foremost grower of boysenberries; Serbia and the wider Balkans grow the blackberry beside the raspberry for juice and wine; and southern Chile gathers an abundant naturalised crop. Around all of this the blackberry keeps an extraordinarily deep body of regional tradition for so lately cultivated a fruit: the blackberry and apple crumble and the bramble jelly of Britain, the blackberry cobbler and the jam cake of the American South, the boysenberry pie of California and the boysenberry pavlova of New Zealand, the marionberry pie of Oregon, the agua and the atole of zarzamora in Mexico, the kuchen de mora of Chile, and the blackberry wine of the Balkans. From a wayside weed that no one troubled to plant, the blackberry has become both an everyday fruit of world commerce and a cherished taste of place.