Among the earliest visitors to their gardens each year are Americans of Irish extraction. Undeterred by the blustery wind and cold, shovels in hand, they are observing the proud tradition of planting potatoes on St. Patrick’s Day.

Many Americans know how the failure of the potato crop between 1845 and 1852 caused mass starvation and disease in Ireland, precipitating a huge wave of Irish immigration to the United States. Since then, America’s Irish immigrants and their descendants have contributed mightily to every field in this country: politics (two presidents), law, industry, science, scholarship and the arts.

The Irish people—and their tragedy—have likewise had an extraordinary impact on the potato. The history of the potato—or to call it by its technical name, Solanum tuberosum—begins in the northern Andes, the mountainous terrain spanning Peru, Ecuador, Colombia and Venezuela. For millennia, the potato was a staple food for the region’s indigenous Inca. By the time the Spanish explorer Francisco Pizarro arrived in 1532, the natives were growing a diverse and multicolored assortment of the 200 potato varieties. Like today, potatoes thrived in the elevated regions of the subtropics, where the climate resembles a cool Canadian summer.

Europeans failed, at first, to grasp the potato’s culinary and commercial promise. To the European mind, root crops were somewhat—how do you say?—less estimable vegetables than their aboveground herbaceous cousins or grains. It was Europe’s superstitious common folk who comprised the anti-potato crowd, while French and Italian aristocrats prized the potato as a delicacy, and “earth truffle” and “earth apple”. Court ladies adorned their hair with tiaras of potato blossoms in their hair, a decorative flourish due for a revival.

Back in South America, the Spanish conquerors saw another kind of potential in the potato. Far from being a delicacy, they saw in the compact, long-lasting and nutritious tubers the perfect slave food—a single potato providing sufficient fuel to sustain a native miner an entire day. Colonial British spies took note: marveling at the potato’s productivity and potential as a food source. Before long, the English operatives relayed the news—and doubtless tubers as well—back to England.

Ireland was Britain’s original colony. Seventeenth century English and anglo-Irish landowners saw the spud as the ideal crop to feed the Irish peasants who labored on their estates under conditions akin to slavery. Potatoes, the estate owners rightly reckoned, were cheaper to grow and process than grain, while Ireland’s cool, cloudy summers provided the optimal climate for the potato to thrive. Introduced in County Wicklow around 1640, it was only a few decades before the large, lumpy type of potato became Ireland’s dominant food crop, especially in the populous south. Ninety percent of the Irish depended on the potato as their primary means of subsistence and livelihood.

The adoption of the potato in Ireland gave rise to one of history’s dark ironies. Until the fatal blight, Irish peasants thrived on their diet of fresh and earthy potatoes, on average consuming five to ten pounds per day. The British, meanwhile, disdained the potato, one of nature’s perfect foods, sticking to a nutrient-poor diet of aged meats and processed grains, such as flour.

The introduction of potatoes caused a dramatic spike in the Irish birth rate. In 1800, Ireland’s population was four and a half million. When the Great Famine began, in 1845, Ireland’s populace numbered 8 million. The diet of potato and dairy products improved Irish health so that, the Irish literally dwarfed the English, the sturdy Celts growing into the “Irish giants” of fact and fiction. The increase in Irish stature, strength and numbers were accompanied by a dramatic decrease in the country’s infant mortality, with six to ten children in the average family.

Originating in a remote valley in Mexico, a pernicious strain of the fungus Phytophthora infestans set sail for Europe with devastating effects. On landing, the resulting disease, called blight, traveled quickly throughout western Europe, beginning in 1845. During the unusually cool, overcast summers of 1846 and 1847, the fungus’s prodigiously infectious spores rode the moist winds. As many of the several dozen potato cultivars in use were related, the fungus ravaged the crops in Ireland and across northern and central Europe. Poland, for example, was only somewhat less hard hit than Ireland. The land-locked Poles starved en masse, while the Irish had had some access to the seas.

The potato, once a godsend for the Irish, became their country’s curse. The Great Potato Famine killed over one million Irish through starvation and disease: more than 12 percent of the population. The acute food shortage and grim prospects caused millions of Irish to emigrate to North America, in search of a better life, surely, but also simply to survive. By 1900, Ireland’s population was down to 3 million, from its peak of 8 million in 1840.

Desperate to explain the wave of destruction, growers and farmers blamed themselves, the soil, the British—even Satan. Part of the most prosperous country in the world, the Irish had solid reasons for holding the British to account. British landowners continued to export grains and livestock from their Irish lands, even as their tenant farmers were dying en masse. A half-hearted British initiative to import American corn to Ireland only slowed the death count, corn lacking the potato’s exceptional range and richness of nutrients.

The 1860s saw a spectacular rebound of Ireland’s potato crop, after Irish and British agriculturists discovered the remedy: breeding new plants from the potatoes that had survived the deadly blight. Out of Ireland’s laboratory of death and misery, tragedy begot triumph. Historians regard the Great Potato Famine as a pivotal point in the evolution of scientific agriculture, helping lead to work like Mendel’s study of garden peas in the 1860s, the science of genetics, and modern agriculture.

In How the Irish Saved Civilization, Thomas Cahill convincingly contends that Irish monks conserved the roots of western civilization. The Irish deserve recognition, too, for their role in conserving one of the world’s greatest food crops, and the horrific sacrifices and suffering that preceded their discovery. On St. Patrick’s Day, let’s remember both the tragedy and triumph of the potato’s epic history in Ireland.