Globalization of economic plant groups
We have distinguished six historically important economic plant groups: cereals and staple crops, spices and medicinal plants, horticultural crops, timber trees, ornamental plants, and naturalized plants.
Globally there are about 3000 known food plants of which about 150 have been extensively cultivated and traded. However, about 90% of the human diet consists of around 15 species and, of these, only four (wheat, rice, maize, and potatoes) make up much more than half of the world’s food supply.
Agricultural cereals & staples
Staple foods are those that make up the bulk of peoples’ diet, the main ones being cereals and root crops like potato and taro and, in a few regions, legumes.
Immense areas of natural vegetation, on all habitable continents, have been replaced by agricultural plants, the transition occurring over many millennia and accelerating in step with the demands of the increasing human population.
Chinese peasants were working the rice-paddies of Central China in 6000 BCE (the likely region of domestication of wild rice). By 1000 BCE it had found its way to India and Sri Lanka, then to northern Africa and southern Europe, to be subsequently transported to the New World by early European settlers. Similar stories of geographic diffusion apply to all the common crops.
After the Neolithic Revolution, farming practices in Europe became more widespread and efficient under Roman administration. At the height of its empire Rome was the world’s largest city with a million residents and, even though a farming nation, wheat was imported across the Mediterranean from Carthage to achieve the complimentary daily ration of bread promised to its citizens. Distant bulk trade in staples had thus now become a necessity for urbanised empires.
The spatial impact of agriculture on the land, and the kinds of plants cultivated, has been greatly affected by technology. In about 1300 across the world lifestyles were similar as most people, except forof the ruling elites, toiled on the land. Worldwide today less than 5% of people are employed in agriculture, a consequence of the Industrial Revolution when people moved from the land to the factories in the cities as the muscle of men and horses was replaced by fossil-fuel-powered machinery.
In England, this social transition was most evident during Queen Victoria’s reign from 1837 to 1901 as scientific and industrial expertise was harnessed to convert a predominantly self-sustaining rural society into an urban industrial society. Over this period, the population nearly doubled from 13 to 24 million. By 1900 the British empire controlled about a quarter of the world’s land surface and a quarter of the world’s population. Despite a program of land reclamation in the early 18th century about a half of England’s food was now imported (along with other resources), from its colonies.
Mostly in the 19th century, in a series of European colonial land grabs (often involving removal of indigenous people and biota), vast areas of the world’s arable land were taken up for agriculture including: eastern and south-western Australia, Tasmania, New Zealand, the Great Plains of the United States, Canada, also parts of Africa, Argentina, Brazil, central India, and elsewhere. The 18th and 19th centuries were a second major phase in the commodification and globalization of plants after the Neolithic Revolution.
Further global food demand was addressed with a Green Revolution (c.1930-1960) when, under large-scale industrial agriculture, many family farms across the world were converted to vast corporate super-farms growing high yield and genetically-engineered varieties.
Imported agriculture also brought unwanted pests, diseases, and invasive organisms that spread out of fields, into rivers, and along roadsides, eventually finding their way into forests and wild vegetation.
Staple crops have had a greater impact on humanity than any other plants. They have provided the life-sustaining energy needed for growth, but their cultivation has made massive demands on the world’s resources while creating irreversible changes to ecosystems. There is more than a grain of truth in the claim that crops have domesticated humans.
Spices & medicinal plants
See also the Silk Road, Silk & Spices, Spices, Botany of spice plants, and the Spice Route
Perhaps surprisingly, it is not food plants but herbs, spices, and medicinal plants that have held a special fascination for humanity. Aromatic and psychoactive plants had mystical properties that connected humans to the gods and spirit world. Along with plant medicines they were, in traditional societies, administered by some kind of ‘medicine man’ – replaced in urban societies by religious and intellectually wise men – priests, apothecaries, physicians and, more recently perhaps, scientists.
Incense, frankincense and myrrh, sourced from the wild, had special religious significance. The tradition of incense-burning, popular in ancient Egypt and Babylon, was also practiced in the ancient civilizations of India and China, and is still important in religious rituals today. Opium was traded in antiquity between plantations on Cyprus and the Egyptian pharaohs in an ancient drug trade. The transparent glassy golden orange amber (obtained as resin from coniferous trees of northern Europe) was associated with the Sun and emitted a pine-like aroma when rubbed or burned.
India, the land of spices, had attracted ancient Babylonians, Assyrians, and Egyptians to the Malabar Coast, the southwest region, Kerala, being a centre for land and sea trade from East and West. Many of these Indian and Far Eastern tropical spices were used as condiments and would become pivotal in world trade and global politics, they included: cardamom, cassia, cinnamon, cloves, mace, nutmeg, pepper, turmeric and, to a lesser extent, ginger, henna, sandalwood, and sesame.
In the West leafy aromatic herbs (origano, parsley, rosemary, sage, thyme etc.), many Mediterranean in origin, were garden favourites. Spices, which were sourced from root, stem, bulb, bark, resin, or seeds were mostly native to the Asian tropics, with chillies, pimento, and vanilla sourced from the Americas (there are notable ‘western’ exceptions such as caraway, cumin, dill, fennel, garlic, juniper, liquorice, mustard, and onion).
Western medicine can be traced from ancient Egypt to the Greek physician Hippocrates and Greco-Roman physician Galen. In the Middle Ages the tradition was perpetuated among scholars of the Islamic world and in the Christian monastery physic gardens that pre-dated the first university medicinal ‘botanic’ gardens of sixteenth century Renaissance Italy when botany was extricating itself from its medicinal origins. Equally influential medicinal plant traditions existed in the ancient Indian and Chinese cultures.
Being controlled by rulers, the wealthy, and religious leaders, spices symbolized social status, becoming prestige luxury goods.
The European Age of Discovery began with a spice race between the dominant European naval powers of the time, Portugal and Spain, as they attempted to find a sea lane that would by-pass the Arab merchants controlling the overland Spice route. The goal was the source of nutmeg and cloves but their location on the Indonesian Molucca islands of the Banda and Molucca Seas was an Arab trade secret.
Seafaring trade had long connected India with South East Asia and the islands of the Indonesian Archipelago. Indonesian trade was, from the 8th to the 12th centuries, in the hands of the Sumatra-based Buddhist-Hindu Srivijaya culture subsequently taken over by the Mohavajit Empires. Arab, Persian, and Indian traders had ensured the creation of sultanates in the region so by the 15th century Malacca, on the Malay Peninsula, was an entrepôt for Muslim trade between the Indian Ocean, Java Sea, and South China Sea. Further eastward in southern Sulawesi was Ujung Pandang (Makassar) a multi-racial multi-religious spice entrepôt.
Sailing westward Spaniard Columbus stumbled into the Bahamas, Hispaniola, and Cuba in 1492 and was convinced that he had reached the Spice Islands. This voyage had major ramifications, opening up the Atlantic to commerce between the Americas and northwest Europe.
Sailing eastward the Portuguese had rounded the African Cape (Diaz, 1488), then tracked the African east coast before crossing the Indian Ocean to the Malabar coast at Calicut (Da Gama, 1497) then on to Malacca in 1498. In 1500 Lisbon was the spice hub of Europe, but access to nutmeg and cloves was indirect until the Spice Islands were finally located in 1511. By 1515 Portugal had established local trading hubs and coastal forts that commandeered the trade from Lisbon to India, Sri Lanka, Malacca, and the Moluccas and in 1517 trade with China began. The cloves of Moluccan Tidore could now be exchanged for the silver obtained in Mexico and Peru.
Magellan’s Spanish expedition of 1519-1522 was the first to circumnavigate the globe, proving beyond doubt that the world was a sphere. In so doing he had experienced the spatial limits of the world, the physical reality of a finite planet. Back in Europe this helped generate the desire to begin an inventory of the world’s biological resources, initiating an era of taxonomy and, in the case of plants, flora-writing.
China discouraged trade with Europe at this time but an opportunity arose when, in 1557, a Portuguese naval base was permitted in Macao. Ships now brought spices from Malacca and traded silks and gold with southern Japan. Gradually maritime trade with the West increased.
To control Malacca and Makassar was to control the spice trade. In the 16-18th centuries first Portugal then the Netherlands seized these ports, the Dutch East India Company building its own trading hub, Batavia (today’s Jakarta) in 1619.
France and England then combined strategic and economic interests with Enlightenment ideals when they launched voyages of scientific exploration to the Pacific and East Indies, England taking possession of the Australian continent and many of the surrounding islands. Portuguese, Dutch, and subsequent British influence in the region still remains together with the Spanish Philippines and its trading centre in Manila.
Spice interests in the Far East eventually declined as plants were smuggled away and grown elsewhere as trade quickly diversified.
Herbs, spices, and medicinal plants have occupied little of the world’s land space. Their significance lies in the role they have played within human culture, not least of which being the development of plant science. Spices helped forge trade links between cultures in the ancient world and between East and West along the Silk Road. The quest for nutmeg and cloves was Europe’s first step on the path to the Great Divergence.
Bronze Age civilizations had grown an assortment of horticultural crops, sometimes in market gardens. The Bible’s Book of Numbers describes Egypt as ‘the land of Figs, Vines, and Pomegranates’. Pomegranates recovered from archaeological sites had 4 chambers instead of the 6-8 we know today and fruits in general were mostly smaller than those of today (Hawks & Boulger 1928, p. 20).
In the West this tradition was maintained in the Greco-Roman world, the Romans in particular dispersing fruits and vegetables across their empire. Among these plants were almonds, carrots, chestnuts, garlic, globe artichoke, lettuce, onions, and walnuts (Vaughan & Geissler, 1998).
Roman trade included goods passing along the Silk Road. We know that it was not only luxury spices that moved along this corridor but ideas and even disease. Some crops diffused outward in both directions from the centre of the European continent – like apples, carrots, cotton, sesame, lemon, and possibly garlic and the popular domesticated onion. Passing westward from East Asia were the cereals rice, buckwheat, and millet together with the fruits almond, peach, and some citrus. The eggplant (aubergine) first cultivated in India was subsequently used in both China and as a staple of the Islamic world. From the West passing to China were alfalfa, broad beans, peas, spinach, turnips, different citrus and watermelon (Vaughan & Geissler, 1998). Both wheat and barley arrived in China around 1500 BCE to be used mostly in the north in bread, noodles, and dumplings called manti which appear to be a creation of the Silk Road.
During the Middle-Ages Islamic culture controlled trade through the Middle East and much of the Mediterranean region including the Iberian Peninsula, so Arab merchants were the primary agents of worldwide plant exchange at this time. several introductions to Europe arrived via Moorish Spain probably including the eggplant (aubergine), lemon (possibly Roman), lime, pomelo, rice, Seville orange (possibly Roman), and spinach (Vaughan & Geissler, 1998).
We only have to consider the world’s six major plant-based beverages: beer, wine, spirits, tea, coffee, and cola to realize the social and economic impact of horticultural crops on the world.
Following the discovery of the New World and its mineral riches, new trading centres emerged in north-west Europe, West Africa, and the Americas as links in a highly lucrative Atlantic economy. At first this involved just Portugal and Spain as gold and silver obtained in the Americas were used to pay for the silk and other goods obtained from China and the Far East: but the Dutch, French and English soon followed.
The Atlantic economy provided impetus for European colonialism soon diversifying to include timber, and other raw materials, but especially plantation crops and their products. In a clockwise cycle of trade that followed the South Equatorial Current to the Americas and then the Gulf Stream, there were handsome profits at every port of exchange. Goods manufactured in Europe were traded along the African west coast where slaves were taken aboard for the Atlantic crossing to the Americas and Caribbean where they were delivered to the plantations. Plantation products were then loaded up for the journey back to Europe before the cycle was repeated. Slave labour provided products that included tropical cotton, sugar, tobacco, molasses, and rum.
Atlantic trade in plant products gathered momentum in the 17th century with sugar plantations in Brazil expanding into the West Indies. Sugarcane, which is native to SE Asia, possibly domesticated in New Guinea around 6000 BCE, had passed in ancient times to India, then to Egypt, Syria, and Arabia, and from there into Europe, including the Canaries, from whence it was introduced to the New World by Columbus in 1493. Sugar beet, bred for a high sugar content, was to become popular in the 19th century contributing to about one third of the world’s sugar supply.
The socially fashionable tobacco was first grown in plantations in Virginia then Maryland. By the 1830s cotton plantations in southern USA were feeding the hungry textile factories in Britain’s industrial north.
coffee initially cultivated in Portuguese Brazil was later grown by the British in Kenya from about 1895 to the 1920s. Cocoa growing naturally in Central America was established by the Portuguese in Brazil but then by the British in West Africa especially in Ghana and the Ivory Coast where palm oil was also sourced. To these products we can add the Rubber plant from Brazil, quinine from Bolivia, Ecuador, and Peru, and sisal from South America.
Food crops new to Europe and obtained from South America and the Caribbean included avocado, cashew, cassava, chilli peppers, cocoa, Jerusalem artichoke, Lima bean, peanuts, pineapple, pumpkin, French and runner beans, squash, sunflower, sweet potato, and vanilla – but perhaps most notably the tomato and potato (Vaughan & Geissler, 1998). Old world crops taken to the New World included the apple, apricot, eggplant (aubergine), cabbage, chick pea, citrus, coffee, grapes, mango, olives, onions, peaches, pears, spinach, sugarbeet, and tea. From Africa came sorghum, henna, and watermelons.
Exchange of animals and plants between Europe and the Americas included not only agricultural and horticultural crops but their commensals and diseases in a fusion of Old World and New World biology that we now know as the ‘Columbian Exchange’, named after Christopher Columbus (Crosby, 2004).
European maritime exploration had soon secured the Cape of Good Hope as a stepping-stone to the East – not only the Indian Ocean and the spices of Sri Lanka and India’s west coast where the Portuguese established settlements and medicinal gardens, but beyond to the trading networks of East Asia.
Traditional trade in the Indonesian Archipelago was based on rice, copra, sago, and spices. Moving westward were camphorwood, cinnamon, cloves, mace, nutmeg, pepper, and sandalwood which were exchanged for gold and silver, Chinese porcelain and silk, and Indian textiles.
Plants transported from Southeast Asia included the banana, breadfruit, citrus, coconut, sugar, taro, yams, and plantains and, from China, millet and soybean. In the sixteenth century the banana was introduced to the Americas by the Portuguese via West Africa and the Canaries but it would remain an exotic luxury novelty in temperate Europe until the advent of rapid transport and refrigeration in the twentieth century. Asian fibres included hemp and jute.
Enlightenment French and English voyages of scientific exploration in the southern Pacific would take possession of further territories including Australia, Tasmania, New Zealand, and New Caledonia.
The Dutch had established rubber in Sumatra and coffee in Java and Sri Lanka. By the 19th century it was tea, rice, and rubber that made up much of the cargoes of the powerful Dutch and British East India Companies, made more efficient with the opening of the Suez Canal in 1869. By the 1870s the British Raj in India had had vibrant trading hubs in Madras, Calcutta, New Delhi, and Bombay along with tea and coffee plantations.
Enlightenment scientific interest in economic botany had developed out of Dutch colonial interests in tropical botany with plant hunters, gardeners, and botanists joining voyages of scientific exploration.
Botanic gardens played a major role in the initial discovery, introduction, and distribution of horticultural crops, colonial gardens playing a major role in the success of sugar cane, coffee, tea, rubber, and forest trees (McCracken pp. 137-143). Philip Miller (1691-1771), chief gardener at the Chelsea Physic Garden, excelled in the initial cultivation of melons, paw-paws, and pineapples in glasshouse hot-beds. But novelties and curiosities would turn into major industries. The Royal Horticultural Society’s Plant hunter Robert Fortune in 1848 successfully used Wardian cases to move towards 20,000 tea plants from China to India as a foundation for the Assam and Sikkim tea industries, the Wardian case also being used by the British and Dutch to transport the Quinine Tree Cinchona from Bolivia to Java and India, Rubber Tree, Hevea brasiliensis from South America via Kew to Malaysia and Ceylon, Cavendish Banana, Musa acuminata, from China to Chatsworth Gardens to Samoa, even the Mango, Mangifera indica, as grafted trees transported in the late 1840s from India to Queensland Australia (Keogh, 2017). Keogh (2017) also reports that Berlin Botanic Gardens were playing an increasing role in the trading of horticultural crops between Europe, Africa and New Guinea (Sisal transported from Central America to Africa by the German East Africa Company), while in France the Jardin d’Agronomie Tropicale in Paris had become a French colonial centre for crop research, and Holland’s Leiden and Amsterdam gardens a stepping stone for crops like cinnamon, mango, and ginger on their way to the Bogor Botanic garden in Java and thence into Asia.
In the course of the Age of Discovery, the traditional botanic gardens changed from medicinal garden to botanic institution, incorporating plant novelties, demonstrating plant classification systems, and contributing to plant inventory through scientific taxonomy, floras, catalogues, and an international seed exchange (active until recent times). In the tropics these gardens were experimental and provisioning stations, holding bays for plant novelties on their way to European gardens and for tropical crops passing between the East and West Indies.
Major European city botanic gardens were administration centres for plant collecting and economic botany in the 18th and 19th centuries. The Jardin des Plantes in Paris introduced coffee to the West Indies from a plant sent to Louis XIV as a gift from the Dutch government in 1714, the plant itself derived in turn from one sent to the Amsterdam Botanic Gardens from Java in 1706. Gardeners and botanists from Kew Gardens in London, under the watchful eye of Joseph Banks (1743-1820), joined Enlightenment voyages of scientific discovery as did those of the Jardin des Plantes in Paris overseen by André Thouin (1746-1824). Rubber plants were cultivated at Kew before distribution to Singapore and Sri Lanka, and Kew was also instrumental in the introduction of quinine to India. Breadfruit was transferred by Britain’s Captain Bligh from Tahiti to St Vincent Botanic Gardens in the West Indies in 1793, intended as a staple food for the slaves in the plantations. Cassava (tapioca) was transported to Asia from South America via the Mauritius Botanic Garden in 1736, and thence to Calcutta Botanic Garden.
Over the long term the world’s forests have undergone natural expansion and contraction in response to ice ages and climate change. Human influence on this natural process began with the Neolithic clearing for agriculture and grazing and we assume heavy deforestation resulting from the human demand for fuel as depletion of woodland around cities is well known from ancient history.
Forests cover about 30% of the Earth’s land surface. About 36% of this area is native forest and 13% is legally protected (World Bank, 2017). Though only about 5% of forests (which cover about 30% of the world’s land surface) consist of timber plantations, a far greater percentage is actively managed, enclosed, or only semi-natural(World Bank, 2017b).
By the 11th century BCE forests around cities in Palestine and Asia Minor (western Turkey) had been plundered. Hills around ancient Athens and Rome were denuded creating erosion problems so that timber had to be sourced from distant locations.
Fernow (2011) noted the usual pattern of forestry development beginning with clearing for agriculture followed by a phase of protection, then more strategic silvicultural techniques including selective logging, enclosure, timber plantations, reafforestation etc. He also reported that Britain, once ‘heavily forested’ , in the early 20th century had forests covering only about 4% of the land as one of the least forested of European countries at that time. This has expanded to about 13% today (Forests Commission, 2017). Australia has lost over 40% of its forests since European settlement (World Bank, 2017). In contrast in Japan human impact on Japanese forests was reduced during shogun rule (1603-1867) and since the end of the 19th century improved forest management has resulted in 68% forest cover.
Tree plantations and forest management practices in the West were established mostly in the 18th century, most notably in Britain and France, but also in the British Empire and tropics. By the 19th and 20th centuries forestry practices were being subject to increasing government control across the British Empire, United States, and Europe.
Modern technology using bulldozers, chain saws, railway networks and logging trucks means large areas can be cleared in very short time, a matter of global concern. Since 2003 the United Nations Food and Agriculture Organization has provided policy advice on sustainable forest management.
For more background see Future gardening, British horticultural legacy, Nurseries & networks, Plant domestication
All cultures have admired plants for their beauty. From antiquity we know of a few plants that were given special status in cultural histories. Roses were popular in ancient Egyptian, Greco-Roman, Persian and Islamic cultures. Then there is the Chrysanthemum of China and the two sacred lotuses, one of Egypt (Nymphaea), the other of India (Nelumbo).
However, ever since Greek philosopher Theophrastus it has been Europeans who have indulged a scientific, not just utilitarian and aesthetic, interest in plants. This intellectual curiosity has been combined with an idiosyncratic acquisitiveness as plant collections have accumulated in herbaria, museums, botanic gardens, plant nurseries, and home gardens.
Though gardens date back to the Bronze Age in the West, the Romans took garden aesthetics to new highs. But the fascination with plant trophies, the ‘beautiful, curious, and new’ began in earnest in the 16th century, accelerating through the Age of Discovery, and culminating in an 18th century plant lust and collectomania sometimes called ‘botanophilia’. This was a movement headed by celebrated personalities like Englishman Joseph Banks and France’s Empress Josephine Bonaparte. The wealthy and influential in Europe all wanted a share of the world’s botanical bounty but, as with the spices before them, it was some time before these plants would trickle down to the lower social strata. The populist democratic horticulture we know today did not arrive until after World War II.
Parks and gardens take up little planetary space but they incorporate many different kinds of plants. We can get an idea of the botanical scale of this by following the global plant stocktake that has taken place over time.
We have inherited from antiquity just a few key plant inventories, each one adding to the names of the past. They begin with medicinal plants listed on Egyptian papyri (c. 2000-1000 BCE) and the works of Hippocrates (c. 460 – c. 370 BCE), followed by the more general listings produced by Theophrastus (c. 371 – c. 287 BCE) and Pliny the Elder (c. 23-79 CE), and the Materia Medica of Dioscorides (c. 40 – 90 CE). At the time of the Roman Empire about 1,350 different plants had been recorded in the West.
During the 16th and 17th centuries in Europe, botanical science had emerged from its medicinal origins and was laying the foundations for plant inventory – its system of classification and nomenclature. Botanists were describing new species, speculating about the possible number of different plants in the world, and publishing lists of existing species – 4,000 in 1613 (Jean Bauhin), and 6,000 in 1623 (Gaspard Bauhin). English botanist John Ray listed some 18,700 different kinds of plants in his three-volume Historia Plantarum (1686-1704). Frenchman Louis-François Jauffret estimated in 1790 that there were at that time about 25,000 species known to science. In 1753 Carl Linnaeus, Europe’s most renowned naturalist of the 18thcentury, a few decades before Australian settlement by Europeans, had estimated that the total number of plant species in the world was unlikely to exceed 10,000 (Stearn, 1959).
It was soon apparent that Linnaeus had made a gross underestimate as plants flooded into Europe at the end of the 18th century. Then, between 1829 and 1933 Britain greatly extended existing plant knowledge as Kew botanists published a series of floras (effectively a stocktake of plants growing within the British Empire). They were floras of North America, Antarctica, New Zealand, Tasmania, British West Indies, Sri Lanka (Ceylon), the Cape of South Africa, Hong Kong, Australia, and British India.
Today the total number of naturally-occurring seed plant taxa in the world is estimated at about 374,000 (RBG Kew, 2016).
Among the first books to be printed in the 15th century were the compendia of medicinal and garden plants called herbals in a tradition that lasted from about 1470 to 1670. Most of these borrowed heavily from Dioscorides and plagiarized one-another’s work and illustrations. We can count the 500 to 1,000 species described in these volumes as the recorded legacy of cultivated plants bequeathed to the modern world from Classical times (Morton, 1981, p. 175).
Plant exchange between countries has been a two-way process but in the case of ornamental plant species this was mostly an inflow to Europe, beginning in the 16th century with colonial exploration and expansion – part of the accelerating process of globalization. Waves of new plants arrived in gardens as Europe extended its geographic influence outwards (Stearn, 1965):
• To 1560 – European-Mediterranean Period
• 1560-1620 – Near East (mostly bulbs)
• 1620-1686 – Herbaceous plants from Canada and Virginia
• 1687-1772 – Cape of South Africa
• 1687-1772 – North American trees and shrubs
• 1772-1820 – Australian plants
Stearn increased the number of periods to nine, his additional three periods being:
• 1820-1900 – tropical glasshouse plants and hardy plants from Japan and North America
• 1900-1930 – plants from West China
An additional pair of non-geographic but important categories of cultivated plants can be added:
• 1930s-> – genetics and plant breeding producing new garden varieties
• 1980-> – genetically engineered plants
Though Portugal and Spain had gardening traditions it was mainly the Netherlands and its botanic gardens at Leiden and Amsterdam that set the European trend for the plant collection and gardening that would follow, acquiring plants collected overseas and making a special study of those from the tropics. With a change in political fortunes it then became France and Britain that would dictate the character of fashionable horticulture and botany.
By the 1730s England was the acknowledged horticultural capital of Europe with the Chelsea Physic Garden holding Europe’s most extensive plant collection. A 1750 preface to a German language edition of Miller’s Dictionary of Gardening (Miller was in charge of the Chelsea Physic Garden and the Dictionary was a monumental compendium of garden plants of the day) declared that: ‘The British are all, more or less, gardeners’ (cited in Wulf, 2009, p. 136).
From the 18th century in England a new affluent middle class of merchants and professionals joined the upper echelons of society in the socially prestigious activity of gardening. This was reflected in the rapidly increasing number of commercial plant nurseries. In the reign of Charles I (1600-1649), London had about five small nurseries and seed suppliers, these numbers rising to around 15 by 1700, and 35 in 1730 when nurseries were starting up in the provinces. In Georgian England (1713-1830) by 1760 there were around 42 nurseries in London and 40 in the provinces including distant places like Edinburgh and Yorkshire. By 1780 printed directories were being produced (Harvey, 1974, pp. 4-6).
In late Georgian England the number of commercial plant nurseries soared. As the Industrial Revolution progressed so too did communication by transport and the printed word, so that by 1839 garden chronicler John Loudon could list 18,000 species cultivated in Britain (Harvey, 1974, p. 128). Similar developments were taking place on the continent and in the colonies. The numbers of new species and cultivars available would continue to climb.
The 19th century then combined a rapid increase in global population with the successes of industry, along with vastly improved technology, communication, and transport systems all integrated into Britain’s relatively stable and flourishing global economic empire. As a result of inventions like the Wardian case. Nurseryman George Loddiges (1786-1846) ‘… put into circulation over 500 cases to all parts of the globe’ and ‘… it is estimated that in just 15 years William Hooker, director of the Gardens at Kew from 1841 to 1865, imported more plants than in the previous century‘ (Keogh, 2017). Attention was on homeland plant acquisition but clearly plant exchange was in two directions.
Today Britain’s native flora numbers about 1,500 species but since the number of plants growing in the wild totals about 3850 then more than half of these are naturalised aliens. By contrast the different kinds of garden plants alone (including cultivars) numbers well over 120,000 (Armitage, 2015, pers. comm.).
Australia has a flora of about 29,000 species and of this about 13% (~3,750) is naturalised. Of these naturalized plants about 60% are garden escapes.
Weeds are plants growing where they are not wanted, whether that be in the wild, in commercial crops, gardens, or elsewhere. Weeds, as defined here, are, in broad terms, plants ultimately originating from cultivation or human agency so for our purposes they are part of global cultivated plant geography. They are an odd category of plants that have, literally, escaped from the formal (intended) process of cultivated plant transfer.
Our interest in weeds is, in the first instance, in terms of their impacts. Their management requires that we understand their origins and biology but a first step is to develop estimates of their proportions in relation to the other major plant groups.
Citations & notes
 Jauffret, L-F. 1790. Projet … cited in Bataski, Y., Cahalan, S.B. & Tchikine, A. 2016. The botany of empire in the long eighteenth century. Dumbarton Oaks: Washington
 World Bank 2017b. https://data.worldbank.org Accessed 17 Aug. 2018
Hawks, E. & Boulger, G.S. 1928. Pioneers of Plant Study. Sheldon Press: London
Keoh, L. 2017. The Wardian Case: How a Simple Box Moved the Plant Kingdom. Arnoldia 74(4): 2-13
Roach, F.A. 1985. Cultivated fruits of Britain: their origin and history. Blackwell: Oxford
As part of the colonial botanic garden era agri-horticultural societies were established in India at Calcutta and Madras in 1820 and elsewhere.