I am a grocery-list-captured male shopper. If something is not on the grocery list, it most likely does not go into the shopping cart. There is one item, though, for which I make an exception. Whether it is on the list or not, I always get a pack of mushrooms because I love them. I love mushrooms in my soup, in my burgers, on my toast, or just sauteed with garlic1.
Given the short shelf life of mushrooms and their fragility, I had always assumed that most of the mushrooms I buy must be coming from some nearby place in California.
I recently learned that Canada’s mushroom production has been growing over the last 20 years, and much of it is exported to the United States, while production in the United States has declined. Differences in policy toward migrant workers between the United States and Canada, and differences in investments in new technology may explain the divergence in mushroom production between the two countries.
But before we get into the details, it is important to understand where and how mushrooms are grown, harvested, and shipped.
US mushroom production
You would be surprised to learn that almost 69% of the US mushroom production occurs in the borough of Kennett Square, Pennsylvania. It is a small town of about 6000 people, but mushroom-growing facilities around town produce almost 451 million pounds of mushrooms annually (2024). 451 million pounds of mushrooms would occupy about 45 American football fields or 35 soccer fields. The dollar value of mushroom production in the US is roughly $ 1 billion per year.
China is the undisputed leader in mushroom production. China accounts for 93% of the world’s global mushroom production.
The history of mushroom farming in Kennett Square dates back to 1885, when a grower obtained mushroom spores from Europe and began growing mushrooms. This concentration of mushroom farming in Kennett Square, Pennsylvania, is due to historical immigration patterns, primarily of Italians in the 1950s or 1960s, easy availability of horse manure for the mushroom substrate, an easy access to the Philadelphia and New York markets.
Growers use an old system called “Pennsylvania doubles” to grow mushrooms. Specialized, two-story cinderblock buildings with wooden shelves and intensive manual picking characterize the system. The system is designed with the assumption of cheap labor.
The growing houses provide a strictly controlled environment for growing white button, cremini, and portobello mushrooms on stacked beds, producing approximately 400 to 500 million pounds of mushrooms annually. Growers can manage the temperature, humidity, and airflow to create optimal conditions for mushroom mycelium to grow and fruit.
The houses are equipped with vertical wooden or aluminum shelves, which maximize growing space. The shelves house pasteurized compost (often made from hay, straw, poultry litter, and cocoa shells) used to grow mushrooms year-round.
As you can see in the video below, the conditions inside the mushroom-growing facilities are hot, humid, and stinky! The process of harvesting mushrooms is fairly manual, unless the grower has invested in a robotic harvesting system from companies like 4AG Robotics. Most US production facilities lack an automation design.
Mushroom shelf life dictates the supply chain
Mushrooms are a type of fungus. If you have the right spawn available and can control the environment economically, you can grow mushrooms year-round. Mushrooms have a short shelf life. Mushrooms are 92% water. A mushroom starts losing water as soon as it is harvested. Anyone who has seen a fresh mushroom that has begun to dehydrate knows how unappetizing it can look.
The dominant mushroom variety grown in both the U.S. and Canada is called the Agaricus. Your most common mushroom variety in your grocery store, the white and brown button mushrooms, cremini, baby bellas, and portobello, all belong to the Agaricus family. The Agaricus family accounts for more than 90% of mushroom production and sales in North America. Shiitake (my favorite or oyster mushrooms) do not belong to the Agaricus family.
Canada and the United States grow mushrooms year-round in climate-controlled, indoor warehouses. Readers of this newsletter are aware of my massive skepticism about the economic viability of vertical farming, but mushrooms provide a counterexample in which vertical farming actually works. The main difference is that mushrooms are fungi and do not need sunlight for photosynthesis.
Due to supply chain constraints and the limited shelf life of mushrooms post-harvest, most fresh mushroom consumption occurs within a few days of production. For example, mushroom production from Pennsylvania mostly stays within a few days of transit.
Most mushroom production facilities in Canada are located in British Columbia and Ontario, close to the US border, and deliver their products to the northern United States within 36-48 hours of harvest. Production geography relative to population is the structural constraint that neither shelf-life extension nor improved cold chains can fully overcome.
The shelf life of mushrooms is the hard constraint. Fresh button mushrooms have a 7-10 day usable shelf life under an optimal cold chain, beginning at harvest. Mushrooms are a high-respiration-rate product. They consume oxygen, produce CO2, and generate moisture. Every degree of temperature above the ideal range of 34-38 degrees F doubles the respiration rate and halves the effective shelf life. Continuity in temperature from the moment of harvest to when the customer picks it up is a critical supply chain variable.
Mushrooms are fragile and bruise under their own weight. Vibration and pressure can cause bruising in transit. Each bruise initiates a localized decay, which accelerates from the point. It limits the number of handoffs or transfer events, since each event is a risk. Mushrooms can lose quality if they dehydrate or become too heavy, and they require an ideal relative humidity of 90-95%.
The same MAP technology used for packaged salads is also used for mushrooms and can extend their shelf life, though it cannot do much for the product’s fragility or the minimum handling requirements.
So, why is US production dropping while production in Canada is rising, even though 99.6% of Canada’s exports go to the US? A big part of the answer to this question lies in how the United States and Canada provide support to migrant workers who come over to pick mushrooms.
by Rhishi Pethe, SFTW | Read more:
Images:Rhishi Pethe; YouTube: Alan Rockefeller, CC BY-SA 4.0, via Wikimedia Commons
You would be surprised to learn that almost 69% of the US mushroom production occurs in the borough of Kennett Square, Pennsylvania. It is a small town of about 6000 people, but mushroom-growing facilities around town produce almost 451 million pounds of mushrooms annually (2024). 451 million pounds of mushrooms would occupy about 45 American football fields or 35 soccer fields. The dollar value of mushroom production in the US is roughly $ 1 billion per year.
China is the undisputed leader in mushroom production. China accounts for 93% of the world’s global mushroom production.
The history of mushroom farming in Kennett Square dates back to 1885, when a grower obtained mushroom spores from Europe and began growing mushrooms. This concentration of mushroom farming in Kennett Square, Pennsylvania, is due to historical immigration patterns, primarily of Italians in the 1950s or 1960s, easy availability of horse manure for the mushroom substrate, an easy access to the Philadelphia and New York markets.
Growers use an old system called “Pennsylvania doubles” to grow mushrooms. Specialized, two-story cinderblock buildings with wooden shelves and intensive manual picking characterize the system. The system is designed with the assumption of cheap labor.
The growing houses provide a strictly controlled environment for growing white button, cremini, and portobello mushrooms on stacked beds, producing approximately 400 to 500 million pounds of mushrooms annually. Growers can manage the temperature, humidity, and airflow to create optimal conditions for mushroom mycelium to grow and fruit.
The houses are equipped with vertical wooden or aluminum shelves, which maximize growing space. The shelves house pasteurized compost (often made from hay, straw, poultry litter, and cocoa shells) used to grow mushrooms year-round.
As you can see in the video below, the conditions inside the mushroom-growing facilities are hot, humid, and stinky! The process of harvesting mushrooms is fairly manual, unless the grower has invested in a robotic harvesting system from companies like 4AG Robotics. Most US production facilities lack an automation design.
Mushroom shelf life dictates the supply chain
Mushrooms are a type of fungus. If you have the right spawn available and can control the environment economically, you can grow mushrooms year-round. Mushrooms have a short shelf life. Mushrooms are 92% water. A mushroom starts losing water as soon as it is harvested. Anyone who has seen a fresh mushroom that has begun to dehydrate knows how unappetizing it can look.
The dominant mushroom variety grown in both the U.S. and Canada is called the Agaricus. Your most common mushroom variety in your grocery store, the white and brown button mushrooms, cremini, baby bellas, and portobello, all belong to the Agaricus family. The Agaricus family accounts for more than 90% of mushroom production and sales in North America. Shiitake (my favorite or oyster mushrooms) do not belong to the Agaricus family.
Canada and the United States grow mushrooms year-round in climate-controlled, indoor warehouses. Readers of this newsletter are aware of my massive skepticism about the economic viability of vertical farming, but mushrooms provide a counterexample in which vertical farming actually works. The main difference is that mushrooms are fungi and do not need sunlight for photosynthesis.
Due to supply chain constraints and the limited shelf life of mushrooms post-harvest, most fresh mushroom consumption occurs within a few days of production. For example, mushroom production from Pennsylvania mostly stays within a few days of transit.
Most mushroom production facilities in Canada are located in British Columbia and Ontario, close to the US border, and deliver their products to the northern United States within 36-48 hours of harvest. Production geography relative to population is the structural constraint that neither shelf-life extension nor improved cold chains can fully overcome.
The shelf life of mushrooms is the hard constraint. Fresh button mushrooms have a 7-10 day usable shelf life under an optimal cold chain, beginning at harvest. Mushrooms are a high-respiration-rate product. They consume oxygen, produce CO2, and generate moisture. Every degree of temperature above the ideal range of 34-38 degrees F doubles the respiration rate and halves the effective shelf life. Continuity in temperature from the moment of harvest to when the customer picks it up is a critical supply chain variable.
Mushrooms are fragile and bruise under their own weight. Vibration and pressure can cause bruising in transit. Each bruise initiates a localized decay, which accelerates from the point. It limits the number of handoffs or transfer events, since each event is a risk. Mushrooms can lose quality if they dehydrate or become too heavy, and they require an ideal relative humidity of 90-95%.
The same MAP technology used for packaged salads is also used for mushrooms and can extend their shelf life, though it cannot do much for the product’s fragility or the minimum handling requirements.
So, why is US production dropping while production in Canada is rising, even though 99.6% of Canada’s exports go to the US? A big part of the answer to this question lies in how the United States and Canada provide support to migrant workers who come over to pick mushrooms.
by Rhishi Pethe, SFTW | Read more:
Images:Rhishi Pethe; YouTube: Alan Rockefeller, CC BY-SA 4.0, via Wikimedia Commons
