By 1840 potatoes were the most common crop in Ireland taking up as much as twenty-five percent of cropland in some counties. The diet of approximately half of the poorest 8.2 million Irish population was almost exclusively potatoes and an adult male would eat 12 to 14 pounds per day.1 Compounding this level of dependence on a single crop was the fact that Irish potato farming was a monoculture - only a single potato variety was grown: the Lumper. This meant that any plant disease that could infect one plant could potentially infect all. In the late summer of 1845 that disease was introduced into Ireland in the form of the "Late blight" - Phtyophthora infestans. Within months what had been a bumper crop was cut in half by the blight.
"Late blight" is a fungal infection - a fact not understood in 1845.
Note that the contemporary Dublin news article at left refers to a
"cholera" in the potatoes.
1 The fungus migrated to Ireland
and Europe along with seed stock shipped from the Americas. Airborne
spores quickly spread the infection in Irish fields
the green growth above ground black and causing the infected
potatoes to rot. The fact that the
Lumper variety was particularly susceptible and that its culture was
nearly universal meant a rapid infestation of the year's crop.
Potatoes were easy to grow, even in the rocky, less fertile soils of the Irish uplands. In a report entitled Reclamation of Waste Land, at Baureigh, Queen's County Irish land agent, William Trench, described how peat lands could be reclaimed and turned to highly productive potato farms. Though most farmers and renters operated on a much smaller scale than Trench described and used the older "lazy bed" method pictured below to raise their crops. Potato production soared right along with the Irish population in the decades before the famine. Even so, consumption of potatoes was largely by lower class labourers, small farmers, renters, and stock.
The following summer Land agent William Trench was among the first to warn the English government of the blight and its potential for serious damage. He noted that the early part of the summer had been unusually warm and that potatoes flourished. By mid August, though, the weather had become unseasonably wet and cool and he began to hear reports of damage:
On August 1st of that calamitous year, 1846, I was startled by hearing a sudden and strange rumour that all the potato fields in the district were blighted; and that stench had arisen emanating from their decaying stalks. I immediately rode up to visit my crop, and test the truth of this report; but I found it as luxuriant as ever, in full blossom, the stalks matted across each other with richness, and promising a splendid produce, without any unpleasant smell whatever. On coming down from the mountain, I rode into the lowland country, and there I found the report to be but too true. The leaves of the potatoes on many fields I passed were quite withered, and a strange stench, such as I had never smelt before, but which became a well-known feature in “the blight” for years after, filled the atmosphere adjoining each field of potatoes. The crop of all crops, on which they depended for food, had suddenly melted away, and no adequate arrangements had been made to meet this calamity, the extent of which was so sudden and so terrible that no one had appreciated it in time, and thus thousands perished almost without an effort to save themselves. 2
1) The table of Potato
Consumption breaks the pre famine Irish population down
roughly by social/economic class. Calculate the average rate of
consumption for each labor group; that is, the number of pounds of
potatoes consumed per person within each group.
2) Explore late potato blight on the internet and outline the cause of the disease, how it effects potatoes, and how fast and how it spreads.
3) Which counties in Ireland had the largest and smallest percentage of
land in agricultural use at the time of the famine? Open the  Irish Famine map and Change Styles in the Ireland - Counties layer to map the % Land in Crops 1851. The degree to which potatoes dominated local agriculture varied considerably across Irish counties. Change
Styles in the Ireland - Counties layer and
create a map showing % Acres in Potatoes 1851.
Describe any pattern(s) you note comparing the two maps.
5) Oats was the second leading food crop in Ireland in the decade of the famine; although a large part of it was exported abroad. Create a map similar to the one for potatoes showing the % Acres in Oats 1851. Compare and contrast the two maps noting similarities and differences in the patterns of cultivation of the two crops across the country. What do your observations suggest in terms of the well being of the populations involved?
images from Potato Varieties of Historical Interest in Ireland, Republic
of Ireland. Department of Agriculture, Food & the Marine, 2010,
"Searching for Potatoes,"from Illustrated London News, December 22, 1849 as found at Views of the Famine
1"Disease in the Potato," The Freeman's Journal, September 11, 1845, Dublin, Ireland as found at newspapers.com.
2William Steuart Trench, Realities of Irish Life, London: Longmans, Green, 1868, pp 101-103 as found at Archive.org.