Underground Mushroom Farms | A Visual Essay

47 million years ago, when the sea covered the north of France, limestone banks started to form in the area where Paris now stands. From the 14^th century, this same limestone would be mined. As a result, the operations created vast underground quarry networks, a subterranean city which birthed the buildings above until a number of sinkholes and collapses in the city centre caused the Paris quarries to be closed by decree on September 15, 1776.

From Quarries to Catacombes

As the city expanded and outgrew existing cemeteries in the 18th century, the story of the subterranean world below the City of Light moved on, and the former quarries became the final resting place for many of Paris’ citizens.¹
 

Plan of the Catacombes, drawn by the IGC (Inspection Générale des Carrières) in 1857.

While this continued through the 19th century, in 1820 another industry was born in the catacombs; mushroom farming. The constant temperature, humidity and darkness of the quarries were ideal growing conditions for growing fungi, which grew on rows of nutrient rich horse manure. Quarrymen became farmers, and they cultivated a button mushroom that became famous well beyond the city limits; les Champignons de Paris.² At the height of the industry, there were estimated to be around 2000 farmers working below the city’s streets.³

With the development of the Paris metro tunnels and the original quarries falling into disrepair, the cultivation of Paris' catacomb mushrooms declined, and very few producers remain today; none operate within the original quarries below the city.² However, both in France and around the world, mushrooms continue to be cultivated in unusual subterranean locations; from historic natural caves, to abandoned underground urban carparks, and disused quarries. Those in the know believe the flavour of mushrooms grown in these locations is superior; the constant temperature and humidity as well as the fact that they grow 50% slower underground gives them a richer, more concentrated taste, with less water loss during cooking.⁴ Take a virtual trip with us below the surface to explore more…

Harvesting of cultivated mushrooms (Champignonniere Chalbot-Manuel), France. The classic way of growing mushrooms underground is by creating mushroom beds, also called “Meules” in French. Compost would be laid in long rows of about 30-40cm wide. They were punched with the feet and then the sides were stuffed with the hands as if one were tucking them in with a blanket. The result is long round beds of about 40-50cm high. Photo from Les Merveilles des Sciences et de l'Industrie, by Eugene-Henri Weiss, published by Hachette, Paris, 1926. (Photo credit DEA / ICAS94 / Contributor/Getty Images)

January 1946: A man watering a crop of mushrooms being grown in subterranean caves in the St Peters Mountains, Holland. The caves are man-made, and served as a refuge for the area's inhabitants during the Napoleonic Wars. (Photo by Keystone Features/Getty Images)

Experimental cultivation of mushrooms in a cave who hosts also the museum in a former WWII antiaircraft refuge made in ancient tuff quarry and roman water tanks. Naples, Italy. These caves were also used by Bourbons to link the Royal Palace and military barracks. (Photo credit KONTROLAB /LightRocket/Getty Images)

Carriere Equestre; an abandoned mushroom farm in France. From the 1970s, automation in mushroom fertiliser production saw producers move from traditional meules beds to growing mushrooms in round bags. These bags were mechanically filled with ripe mushroom fertiliser, inoculated with mycelium and taken to the cultivation areas. The plastic was more resistant to the humid climate than wooden beds. (Photo by Bert Beckers)

During the 20^th century, the underground mushroom farming industry spread from Paris to Belgium and The Netherlands. The area of Riemst - Maastricht has countless (+200) underground limestone quarries, and most of these quarries were used as a mushroom farm at some point in time. The industry grew so big that Riemst became one of the largest European providers for underground mushrooms.⁴

A tragic quarry collapse in the De Roosburg mushroom farm, once the largest mushroom nursery in Western Europe, and advances in mushroom growing techniques has meant that today only two underground producers remain in the area; Theo Jennen in Wallonia, and Dirk Jackers in Flanders, Belgium. Both grow their mushrooms in quarries using iron raised beds. The manure is prepared by a composting factory nearby and gets delivered together with the iron beds.⁴

Dirk Jackers is the last underground mushroom farmer in Flanders. Located in a large quarry with high ceilings, the climate is stable and ventilation is done simply using an old airshaft and some large plastic sheets. (Photo by Bert Beckers)

Theo Jennen is the last underground mushroom farmer in Wallonia. Located in a smaller quarry with low ceilings, a more advanced ventilation system is needed, as well as the need to disinfect the galleries every time before setting up a new culture. (Photo by Bert Beckers)