Thousands of years before the Incas developed an empire in the region that now includes Peru, Chile and Bolivia, the local farmers were already cultivating the potato. There are about two hundred species of wild potatoes still growing, but fewer than a dozen are now widely cultivated in the Andes. For most of the world, however, the potato is represented by a single species: Solanum tuberosum.
A number of the plants widely cultivated throughout the world today had their origin in the Americas. Many of the most prominent species belong to the Solanaceae family, including potato, tomato, pepper and tobacco plants. These, for the most part, are tender, warm-climate crops. The potato is an unusual member of this family, coming as it does from a region where frosts can occur even in summer. The potato prefers a cool growing season.
The Andean farmers cultivated other root crops besides the potato, but maize (corn) was considered the mainstay of the diet, as well as the main ingredient from which they brewed an alcoholic drink called chicha. Maize is a tender crop that requires hot summers. The farmers of the Andes grew maize and other warm-season crops in the lowlands, and potatoes in the cooler, drier high valleys and the upland plateau. They even had species that could withstand the frosty conditions of the inhospitable altiplano.
Solanum tuberosum is classified as a herbaceous annual, usually propagated vegetatively, with new plants sprouting from the buds (eyes) on the tubers. The tubers that are planted are known as "seed potatoes," as opposed to "true potato seed" from the potato fruits. Even the most hardy potato plant will be killed by a long hard freeze. There are two main varieties or subspecies of S tuberosum, adapted to different growing conditions. S tuberosum subsp. andigena is the short-day variety that does not set tubers until the days grow shorter in the fall. S tuberosum subsp. tuberosum is the long-day variety that sets its tubers at the height of summer, when the days are over twelve hours long. Today, almost all potatoes cultivated outside South America are of this type.
When Pizarro's conquistadors invaded the Inca empire in 1532, they were looking for gold, not potatoes. Nonetheless, a few specimens of the andigena type were brought to Spain, where they were grown successfully. But for a variety of reasons, the potato was not at first accepted in the New World. As a member of the Solanaceae, the Nightshade family, the potato was considered poisonous, and not entirely without reason. If potato tubers are exposed to sunlight, they develop the toxic alkaloid solanine. But the primary reason was that the Spanish conquerors regarded the tuber as fit only for the consumption of the native Indians and other despised groups such as prisoners and the inmates of hospitals. The potato was lumpy, ugly and grew in the dirt. Also, it wasn't mentioned in the Bible and thus might be of diabolic origin.
But around 1580, the potato was introduced to Ireland. At first glance, the moist climate of Ireland would seem to be unsuitable for a crop that evolved on the arid slopes of the Andes. But the potato thrives on abundant rainfall if it has well-drained soil, and the long, cool growing season in Ireland is perfect for the fall-maturing short-day potato.
The story of the potato in Ireland is one of politics and sociology as well as botany. The typical Irish cottager was a subsistence farmer who had to make a living from a rented plot of land that might be no more than an acre. The only crop possible under this circumstances was the potato, which yields more food value per acre than any other. The combination of potatoes and milk provides a nutritionally complete diet. An Irish cottager with a small plot and a spade could grow enough potatoes to feed a large family and raise a pig, perhaps also to distill a few pots of the homemade liquor called poteen.
The amount of potatoes raised in Ireland increased rapidly throughout the eighteenth century, and so did the number of people who raised them. Between 1780 and 1840, the Irish population doubled from four to eight million. This increase put more pressure on the land and caused rents to rise, leaving as many as a third of the population entirely dependent on smaller plots and the potatoes they could grow on them. By 1840 the variety most commonly grown by the poor cottagers was an inferior but high-yielding potato called the Lumper, an import from Scotland where it had been used only for feeding stock. This degree of monoculture left the Irish potato crop highly vulnerable to disaster.
The 1840s saw the appearance in Europe of the fungus Phytophthora infestans, causing a disease called Late Blight. In 1845, the blight destroyed at least half the Irish potato crop, and in subsequent years until 1850, the disease returned. The result was widespread famine in Ireland, with at least a million deaths from starvation and subsequent disease. Another million emigrated; the Irish population has never recovered to its 1840 level.
The blight devastated potato crops throughout Europe and caused hardship to the degree that the population depended on it for basic sustenance. The country worst affected after Ireland was Holland, but deaths there from blight-related famine were only about nine percent of the Irish toll. Although widespread blight was never again so severe after 1850, it inspired agronomists to seek out possible cures for the disease and to breed resistant strains of potato. By this time, the worldwide importance of the crop was too great to consider abandoning it.
First of all, it was necessary to discover the fungus responsible for the blight. Once this was accomplished, the copper/lime fungicide known as Bordeaux mixture, invented for use in vineyards, was shown to be effective against it. From the end of the nineteenth century, potato cultivation has depended on fungicides.
While farmers in Ireland and the Low Countries had readily adopted the potato, they initially resisted the new crop in many other countries, where governments attempted to introduce it by persuasion or even more forceful measures. In France, a series of famines and failures of the wheat crop in the eighteenth century eventually convinced the government that the potato would be a good hedge against starvation. Antonine-Augustin Parmentier famously surrounded his potato patch with armed guards so that peasants would regard the crop as valuable. In the nineteenth century, after the revolution had resulted in land redistribution to small farmers, the potato gained acceptance.
Parmentier was introduced to the potato when he was a prisoner during the Seven Years War in Prussia. The Prussian King Frederick the Great did not limit himself to suggesting that his peasants grow potatoes, he ordered them to, so that he could supply his army. The Russian Empress Catherine the Great issued a similar order, but it took Nicholas I to enforce it in the mid-nineteenth century.
Despite this initial reluctance, by the end of the nineteenth century northern Europe led the world in both potato production and consumption, including consumption as vodka distilled from the tubers. The growth of the potato in this region was made possible by the development of new, long-day varieties of S tuberosum. The short-day andigena type flourished in the mild climate of Ireland, but in the shorter growing season of the north, with its severe winters, the crop would freeze in fall before the tubers could be harvested. While the long-day potato is native to regions of Chile, European growers apparently bred their own from the short-day varieties.
North America was another country where potato growing was adopted voluntarily by the population. In the colonial period, "potato" originally meant the totally unrelated sweet potato, Ipomoea batatas, which could then only be grown in the southern states. The white potato was introduced in the eighteenth century, where it was known as the Irish potato to distinguish it from the other tuber. By the mid-nineteenth century, with the introduction of long-day varieties, it was the most popular vegetable grown in the US, which it still remains.
Its popularity was greatly boosted when in 1872 the young Luther Burbank accidentally bred the potato now known by his name. This, and its descendant the 'Russet Burbank', is a variety particularly well-suited to baking and frying. The 'Russet Burbank' was first grown in Colorado; the official "Idaho® potato" is the 'Russet Burbank'. The high elevation of this region, its soil and the availability of water for irrigation rapidly made it the center of potato cultivation in the U.S. in the beginning of the twentieth century, with the 'Russet Burbank' the primary crop.
Unfortunately, this region was also the home of the insect that soon become known as the Colorado Potato Beetle, Leptinotarsa decemlineata. It quickly spread to become one of the most serious pests of the crop worldwide, despite quarantine attempts by European governments. The import of American potatoes into Europe during and after WWII is sometimes blamed for its spread into Germany and eastern Europe. In consequence of this and other pests, potato farming in the twentieth century came to involve routine insecticide use as well as fungicides.
Throughout most of the twentieth century, northern Europe led the world in potato production, with Russia in first place. In the last couple of decades, however, potato cultivation has begun on a large scale in Asia. Now, the #1 producer of potatoes in the world is China, which grew twice as much of this crop as Russia in 2007. In third place is India.
This growth in Asian potato production is the result of government plans to increase food production in these highly populous states that have traditionally depended on rice. The rise in worldwide food prices, particularly for grains, has increased the urgency of these projects. In China's northwest region, officials hope that potato cultivation will bring productivity to land subject to recurring drought. In Bangladesh, it is being promoted as a winter crop during the dry season. Increased cultivation is also being promoted in the sub-Saharan and highland regions of Africa.
Because of the rapid expansion of potato culture worldwide, the UN declared 2008 the International Year of the Potato.
While the potato has great promise for relieving world hunger, it would be prudent not to forget the example of Ireland. This crop is still subject to several serious diseases and pests. In 1990, a new race of Phytophthora infestans was discovered, immune to the existing fungicides that have controlled the blight for over a century. As the cultivation of the potato expands worldwide, agronomy is racing to keep up with it in developing new varieties and new methods of cultivation.
Agronomists have returned to the Andes, to the place where the potato originated, to use the many native species for breeding new and desirable traits into the potato, such as resistance to disease and adaptation to different growing zones. One of the most promising developments is the production of true potato seed that will produce reliably. The ability to grow potatoes from true seed would eliminate many problems with seed potato storage and transportation, as well as viruses that can be passed on in the seed tubers.
As the world population keeps rising, new crops and new agricultural methods have to race to keep up with it. The potato could be a solution, but the more a population is dependent on a single, vulnerable crop, the greater the potential for disaster. We do not want to see another world-wide potato famine.
Lang, James. Notes of a Potato Watcher. College Station, 2001.
Zuckerman, Larry. The Potato: How the Humble Spud Rescued the Western World. New York, 1998.
International Potato Center: http://www.cipotato.org/
Peruvian potatoes: ©CIP http://www.cipotato.org
Russet Burbank Potato: © Steve Caruso http://creativecommons.org/licenses/by-sa/2.5/
Marketplace potatoes: by Fir0002/Flagstaffotos http://commons.wikimedia.org/wiki/Commons:Text_of_the_GNU_Free_Documentation_License
Other photos: USDA
The paintings "The Potato Eaters" and "Potato Planters" are by Vincent Van Gogh