The potato was first introduced to Europeans after Cortés and his conquistadores found the New World Incan populace subsisting happily on potatoes along with quinoa, amaranth and maize (corn) in the 1500s. Potatoes are believed to have been systematically hybridized and cultivated by the Incas from 7-10,000 years ago. European sailors first brought potatoes to the Canary Islands and from there to Europe and Asia (and back to North America). Since potatoes are propagated vegetatively, all European varieties of cultivated potatoes are believed to have sprung from the single strain bought to the Canary Islands. There are hundreds of species of edible potatoes, from the southwestern US to the Chile, but only one species has been cultivated outside of South America. The adoption of the potato as a food source has by Europeans been credited with one-quarter of the population growth in Europe from 1700-1900.

Like other medieval people of the Old World (or what we now call Europe and Asia), the Irish grew wheat and barley to sell, to grind into flour for bread and to brew ale and hard liquor. The best land in Ireland was used to grow wheat and to graze cattle, but the Irish grew vegetables, especially cole crops, on the rest. These folks were of Gaelic-speakers of Celtic ancestry.

something completely different

Around the late 1500s, an interesting hot-house plant arrived in Spain, a member of the Solanacea family, a Solanum tuberum specimen from the expeditions to the "New World." It was a member of the "nightshade" family, so they reckoned it must be poisonous (the same assumption was extended to tomatoes). By 1650, the potato had arrived in the greenhouses and ornamental gardens of the Irish gentry, valued mainly for its curiosity value and exotic character.

This new, foreign plant was suspicious since it did not reproduce the familiar way, with normal seeds, but by vegetative starts now known as "seed potatoes." It looked a bit like someone with leprosy, and so was doubly mis-trusted. When it was realized that this new plant thrived in the moist, cool Irish climate, and didn't mind the hills, the farmers began feeding its starchy, swollen tubers to livestock. Ultimately the local Irish began eating this new crop themselves; what began as fodder was converted to food.

"Despite the benefits of potatoes, their widespread adoption did not follow immediately after their first appearance at the end of the sixteenth century....Potatoes were widely adopted as a field crop in Europe towards the end of the seventeenth and beginning of the eighteenth centuries" write Nathan Nunn and Nancy Qian. Ireland began to rely heavily on this new crop; by the first quarter of the 19th century, 1/3 of the population of Ireland subsisted solely on potatoes.

depending on potatoes

With this cheap, new, relatively nutritious food source, the population of Ireland swelled to an all-time high, above 8 million, in about 1840. (Greater nutrition also increases fertility.) Potatoes are called the first modern "convenience food," by the International Potato Center, because the "potato is energy-rich, nutritious [and] easy to grow on small plots." Then, in 1845, the annual fall-harvested potato crop failed. What had already been harvested, rotted, and what was not yet harvested, decayed in the fields. More than one million people are estimated to have died from famine or from an increased vulnerability to endemic diseases like tuberculosis and cholera--some estimates are as high as one-and-a-half million. An additional one million more emigrated or forced to emigrate to other English-speaking countries (like the US, Canada, Australia and New Zealand), all of which now have large "Irish" populations. At least one-quarter of the population of Ireland disappeared.

The reason for the late blight: the fungus-like Phytophthora infestans. This pathogen can complete a life-cycle in 5 days on a potato leaf under optimal conditions (it also infects other Solanacea family members, such as tomatoes). It requires low temperatures and high humidity to live and reproduce. However, frost does not kill the spores living in soil or in stored crops. P. infectans was reported in New York and Philadelphia in 1843, and in early 1845 appeared in a shipment of seed potatoes for Belgian farmers.

The 1845 autumn crop failed, but the Irish were accustomed to having crops fail occasionally. Due the nature of P. infectans, mutating readily and staying alive and contagious in the soil without a host plant, after the first bad harvest things went from bad to worse to horrifying in Ireland. For one thing, there wasn't an uninfected supply from which to draw the next year's seed potatoes.

Because Ireland had been growing only S. tuberosa 'Irish Lumper' during the famine period and propagating seed potatoes that were genetically clones of the parent plant, there were no genes for resistance were bred in to 'Irish Lumper'. Farmers in Ireland and elsewhere in Europe were baffled by this new blight. They did not know the difference between bacteria, virus, fungus and weather; they could not understand why the crops kept failing. Germ theory had yet to be figured out

Other countries also experienced potato crop failures in the the middle of the 19th century, but only Ireland relied so heavily on the potato for nutrition that crop failure meant disaster. "Black '47" is what they called the worst year of the disaster; "over one million had died from malnutrition, slow starvation, rampant disease and escalating despair that did not abate until 1852." writes Sylvaine Gold of the New York Times. Malnourishment meant hungry prople were more susceptible to tubrculosis, typhoid fever, cholera, and diseases of infancy and old age.

take-home message

The potato was a perfect crop for 19th Century Irish peasants because it provided a greater yield on a smaller plot than wheat or other crops. Current "potato promotions in Africa ominously echo the terms in which eighteenth- and nineteenth-century British observers praised the tuber."warns Ellen Messer. in The Cambridge World History of Food. People should be wary of depending on a sole crop that "might lead to a repetition of the Great (nineteenth-century Irish) Hunger." says Messer, The potato, baked, boiled, mashed or fried or fricasséed, is a wonderful vegetable which is nutritious and low calorie enough for even dieters while providing a high yield from a small area of ground. But we must never forget the lessons of an Gorta Mórin as it is known in Gaelic, "the Great Hunger."