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Will it be necessary to rebuild American farms that get 40 kg of mushrooms per square meter?


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UMDIS Mushroom Information Agency recently had the opportunity to attend the Short Mushroom Course in the US and to visit a number of farms in Pennsylvania, where up to 60% of the mushrooms in the United States are grown. So I will share my impressions with you.

Strong marketing, developed logistics and trade, significant and growing concentration of production in a small number of companies, high demand for mushroom farm products. The lack of domestic production is covered by imports from Mexico and Canada. The biggest problems of the industry are a lack of people, an excess of flies and the need to find a replacement for peat.And most of the farms inside the country grow mushrooms in such conditions that if you were inside such a growing room without knowing which country you are in and what time it is outside, the most accurate would be to bet that you are somewhere in Brazil and it is 1950 outside.

But in order. 


In the USA, high yields are obtained from a square meter, often substantially higher than 40 kg. For this, they put a lot of compost per square meter and are not so picky about the quality. Mushroom Business recently published an excellent article by Raymond Samp, a consultant with 60 years of experience in both America and Europe, on the fundamental difference in mushroom production styles in the US and Europe. If you haven’t read it, I highly recommend it. 

The US has much lower environmental requirements than Europe, allowing many states to compost outdoors without worrying about ammonia emissions, noise, or odor. We were on farms near Kennett Square – a small town, the “mushroom capital” of America, as they say here. About half of the mushrooms in the US are grown here – hundreds of small farms are tightly interwoven with residential buildings, large and small composting plants and other suburban infrastructure. Once upon a time, each small farm had its own owner, especially this business was successfully run by people from Italy. But over time, more successful farms bought out less successful ones or for some other reasons, and now the number of farms remained huge, but the number of owners decreased to dozens. Therefore, one company often has a large number of sites scattered around the area under its control. Although the number of small farms has decreased, there are still some individual entrepreneurs who receive compost from larger players and deliver their products to them. We specifically asked to show us the smallest, truly separate and independent, farm in the region – and it turned out to be not so small, with the production of several hundred tons of mushrooms per month. 

The climate in the same Pennsylvania allows you to make good compost all year round in the open ground. Although some composting plants use bunkers in the production of phase 1 compost, others do without them at all. And even when there are bunkers, compost spends a good half of the time in heaps and piles on nearby sites. 

Compost plants use as raw materials horse manure on straw, straw, corn stalks, corn cobs, chicken droppings, mixing everything and adding water. Mixing lines typical for Europe are not used here, but mixing is done with the help of loaders, hoppers, and pile formers. Water is added in the process. At the large Giorgi compost plant we visited, there is also a ceiling system for loading compost, which accordingly also performs mixing during compost turn. 

The most noticeable difference between the compost here and in Europe is that it is much more fermented and shorter. This is what allows you to then put the standard 120 (for phase 2) and sometimes more kilograms of compost per square meter on the growing shelves. When Phase 1 compost is put on the shelf, and there are still many such farms left, the amount of compost per square meter is increased by another 10-20 kg. Such, more fermented compost is more stable on the shelf of the mushroom farm, and it is possible to keep the temperature in an acceptable range. 

Efforts to grow in the US on Phase 3 compost seem to have failed so far, and most mushrooms are now grown on Phase 2 compost, and there are still a large number of farms that load Phase 1 on shelves and pasteurize in growing rooms. 

In general, everything is quite clear with compost – not burdening yourself with too many environmental regulations, having enough raw materials, not too expensive energy sources, enough land, the possibility to sell  or use Phase 2 or Phase 1 compost, simpler and less tidy, so to speak, the appearance of compost plants appears fully justified. That definitely cannot be said about growing rooms. 

Growing rooms 

If you imagine that a European mushroom grower got into an American growing room without any prior idea of ​​what they look like, he would be in astonishment. Wooden racks that are 40-50 years old, simple front and back doors, no stationary lighting, no clean/dirty corridors, no carts for collecting mushrooms, no irrigation systems. At the same time, the standard growing room, which they call “American double”, is four seven-tier racks with a total area of ​​about 600 m2, where they put about 80 tons of compost. The air duct standard is a wooden box in the center of the room, from which the nozzles exit both down and to the sides, although there are different options. Each room has a separate climate unit, usually installed outdoors behind the growing room. At the level of 4th shelf, the racks are connected by beams, on which wooden bars are placed, on which you can walk – in this way, the room is divided into the lower part, into three shelves in height, and the upper part, where at the level of the “floor” – wooden bars there is the fourth shelf and three more shelves above. Interestingly, to collect 4th shelf, pickers simply sit on the “floor” of the second floor, dangling their feet on the first floor between the wooden lattice and the rack. 

On one of the farms, we were shown a working growing room, which is in the photo from the 1920s. There may not be many “hundred-year-old” growing rooms here, but there are definitely quite a few 50-year-old ones. Previously, rooms were loaded manually, but now the loading and unloading of rooms is largely mechanized. The truck feeds the compost to a narrow mobile conveyor that feeds it into the room through a narrow door located opposite the passage between the racks in the back of the room (there are two such doors for two pairs of racks). The conveyor from the street ends at the beginning of the rack, where it is joined from below by a transverse small conveyor that throws compost onto the rack on the left or right of the aisle. A net moves along the shelf, which is pulled from the other side of the room by a suspended winch, and a man with pitchforks helps the compost to be distributed more evenly across the width of the shelf than the transverse conveyor itself manages to spread. 

Loading is surprisingly fast. By eye, the loading of compost onto the shelf occurs at the same speed as during the operation of a standard “European” filling machine, although the number of people involved is greater – it seems that 8 people managed it. Their work is not easy. The disadvantage compared to a filling machine is that after such loading, two more operations cannot be dispensed with – first leveling with forks, then with a ruffling machine, and then tamping with a tamping machine. One way or another, the result of such loading is not as uniform as that of a filling machine and, most importantly, it is much more labor consuming. And what is important, greater labor intensity is expressed not only in a greater number of man-hours, but also in what they are spent on – smoking while watching the flow of compost on the filling machine while sitting in a warm corridor and turning the handle of the height of the shaft – this is not at all waving pitchforks for 4 hours in a row (European farm loading crews, I know – your job isn’t sugar either). Lighting is temporary, during loading, a garland and, if not enough, a flashlight on the forehead. 

The standard width of the shelves is also larger than in Europe – 1.5 m instead of 1.34 m commonly used in Europe. 

The compost is then incubated for 10-12 days – so fast because almost everyone uses synthetic speed spawn, and the application rate also seems to be much higher (I was counting from units (bags) to the room for a long time when loading so many pounds per foot, and in in the end I was satisfied with the result “much more”). 

A supplement is usually added to Phase 2 compost. This is possible in great extent because the compost, if you look at it through the European experience, is over-fermented, and therefore not so active, and even at 120 kg per m2, overheating can be prevented. Usually. Then the casing soil is applied manually or semi-automatically – necessarily with the use of industrial CI (instead of mixing incubated compost into the casing, which is usual for Europe). 

After that, manual watering (I guess be with a flashlight on the forehead) and waiting for the harvest under the intense control of the technologist (with a flashlight of course). 

The harvest on the shelves looks quite unusual. There are often a lot of mushrooms, it seemed to me that in America mushrooms have much less need to grow vertically 😊. This is because a good half of the mushrooms are brown strains, where a large part of the crop needs to be open (portobello) and they allow them to grow on top of each other. 


Temporary lighting in the form of long LED lamps is installed in the room. But since the shelves are wide and there are not many lamps, there are also flashlights on the forehead. For collection, either boxes with nested boxes are used, or simply boxes, not some farms of a special shape – which are nested one inside the other. They don’t particularly bother with calibration, and in general, the average size of mushrooms in America is larger – in stores, most of the space is occupied by sizes of 5-6 cm, but there are many and various others, in particular, large white and portobello are also enough on store shelves. Instead of the mobile picking lorries usual in Europe, ladders are used here, and the boxes holder is usually hung on the side of the rack. The quality of cutting is different, it is not bad, but rather it can be said that it meets local standards. Based on the number of stems on the floor, one might think that many collectors cut them straight to the floor. The product itself – mushrooms collected in boxes – looks decent enough, although not at all as rigidly standardized as the product coming out of mushroom growing rooms in Europe. Remains of peat, lack of laying, dirtier mushroom, greater difference in sizes in one package than we are used to – this is acceptable for the local market. 

Packing houses 

In fruits, vegetables, mushrooms, there is such a rule – if the product has a certain consumer quality after harvesting, it is impossible to improve it with post-harvest processing. It seems that this rule does not work here. Modern packhouses seem to be able to make absolutely attractive packages of a product ready for distribution to supermarkets from a rather mediocre product coming from the farm. 

It is interesting that in the warehouse we visited, where about 100 tons of mushrooms are packed per day, the mushrooms are packed warm. It is packed in a film without prior cooling. The film, in addition to being breathable in itself, contains several rows of holes approximately 5 mm in diameter. After packing, the packed mushrooms are cooled by vacuum cooling. Managers explained to us that these holes are a requirement of the legislation, and they would be happy to get rid of them, which would allow to extend the shelf life. But it seems that vacuum cooling would be difficult without these holes. Packaging branded with the trademark of the manufacturer is a rather insignificant part of the assortment. Its basis is the trademarks of retail chains. Different package sizes, different mushrooms, sliced ​​and whole – only in this Giorgi mushrooms warehouse, the shelf with labels contains more than 350 different labels. And it occupies an entire pavilion. In general, the packing facility is completely modern, unlike the growing rooms from which the mushrooms come. Let’s get back to them, the growing rooms. 

…growing rooms The hygiene of classic rooms is based on the mandatory cookouts (steaming). Also, where production is not organic, chemicals are used. Since on all farms without exception, no matter how they look, safety standards have been implemented and relevant certificates have been obtained, traffic and hygiene on farms are sufficiently regulated. To be honest, I don’t quite understand how it works – the cleanliness does not look absolute, wooden racks and a lot of cracks, open mushrooms (spores), a huge number of flies, composts 1 and 2 phases – but the prevalence of diseases is not observed. I think that the answer lies in several points. 1) Deeper fermented and more selective compost 2) Fast synthetic spawn and CI instead of compost in the casing 3) Many years of experience of the whole community 4) … and diseases are still there and not so few. 

Flies are a particular headache for local mushroom growers. Moreover, if Sciarids is more annoying in Europe, then here there are more problems with Phorids. And they cause problems not only to mushroom farms, but also to local residents. Since Kennett Square has hundreds of mushroom growing rooms scattered throughout the area interspersed with residential areas, it’s common for locals to find hundreds of Phorids in their kitchens, we’re told. And since local legislation protects either agricultural production here in general or the mushroom business specifically, complaining to the state about their flies does not lead to a positive effect. The problem is aggravated by the fact that a large part of the farms produce organic mushrooms and cannot use chemical means of protection. Even if someone manages to get rid of “his” flies, there will be no need to wait long for the neighbors’ flies. 

Therefore, the question with flies here is not whether they are there or not, but whether there are many of them or too many. They put seals on the doors, filters on the windows and air conditioning units. It helps to some extent but measuring the number of flies and fighting them is a constant process here. 

As I said, a significant part, tens of percent, of production is organic mushrooms. Moreover, the division into organic or inorganic production begins at the farm – as I was told, all the compost here is organic. There is no requirement for organic production to use organic straw or organic chicken manure in compost production. Therefore, all compost is organic. And to get organic mushrooms, it is enough not to use chemicals in cultivation at mushroom farm. And get certified and fill out a bunch of logs, I guess. 

Brown mushrooms are very popular in the USA. About 40% of the fresh market is brown mushrooms. Moreover, if the most popular variety in Europe is Amycel Heirloom, Amycel Brawn is more often preferred here, which, although it is somewhat inferior (although there is also a debate about this) as Heirloom, is less demanding in terms of growing conditions and technology. And a huge number of brown mushrooms are grown as portobello – that is, with large open caps. Portobello and brown mushrooms (here they are called baby bella or cremini) are a must-have item for supermarkets. All the growing rooms we visited have automatic climate systems. Automation, as a rule, is quite simple, aimed mainly at maintaining a given temperature. Humidity is often controlled “manually and I have not seen automatic CO2 monitoring on any farm. Moreover, there are no external weather stations that allow modern automation systems to save energy resources. Maybe they do it manually based on experience. The conclusion of Raymond Samp, which he makes in the article I mentioned at the beginning of the article – the American type of production is neither worse nor better than the European one, just everything is good for its conditions, and the conditions in the USA are such that the market is happy to accept what is supplied to it. And it seems that this situation will continue, and mushroom productions in the USA will continue to grow mushrooms in their growing rooms with wooden racks without CO2 sensors. 

In principle, American mushroom growers, after the demonstration of growing rooms, do not really wait for the question “how so?!” and immediately begin to tell why they do so. Maybe they don’t wait for the question because it shines in the eyes of a person who is used to seeing growing rooms in Europe. They all explain that this cultivation system has been tested by time, gives predictable and good results, high yields. And that the construction of European-style farms will not pay off, as it requires huge investments, and here everything is already there, built, working, only sometimes repair and change the boards every few to ten years. However, I note that since the companies are already quite large, we met mainly not with owners, but with managers or technologists. So I can’t guarantee that the owners 100% support this opinion. But it definitely sounds like a basic, well-rehearsed answer. 

How the future looks like. 

It is impossible to argue with the fact that something is better for some conditions and not suitable for others. But I am sure that IN 15 YEARS IN THE USA THERE WILL BE NO INDUSTRIAL MUSHROOM GROWING IN CLASSIC “AMERICAN DOUBLE”, i.e. their classic rooms that I described – with wooden racks, a simple climate, flies and no lighting. And this statement contradicts the generally accepted explanation that I voiced in the previous paragraph. 

So, I am sure that in not too many years there will be no more such room. I will explain why. 

The first is people. The problem of finding people to collect mushrooms is already super urgent. The Europeans, with their self-propelled picking lorries, have a very hard time finding people, but the working conditions in the American rooms are obviously worse. Much will depend on the economic situation in the countries and territories south of the US and the US policy in relation to labor migration. But the world has recently been moving towards progress at a rapid pace, and I assume that this will continue. In any case, it will be easier to attract workers to low-paid, monotonous and difficult work for farms where the rooms have light, picking lorries, and better yet the rack itself, it goes by itself and a fly does not climb your shirt collar. They say there have been many attempts to bring Dutch technology to the US and all have failed. Maybe so. But I know for sure that the attempts have not stopped, and someone will break through – and American retail chains will taste a different quality. I do not want to say here that the quality of American mushrooms is insufficient. But different. And supermarkets will like the one offered by European-style farms more. And I think the most important thing is operating costs. I have not studied the accounting books of American mushroom farms, but I am sure that there will not be everything so sweet with the exploitation of such farms. Low-cost airlines, which try to save on everything as much as possible, tend to update their fleets with new planes, rather than buying much cheaper used ones. Because in the long run, the investment in an expensive new plane will pay off due to lower fuel consumption, lower repair costs, less downtime, fewer pilots… I am sure that operating a growing room that needs constant repair, where it is uncomfortable to work, where flies fly in, where you can’t get the maximum harvest because there is no maximum control of the climate and uniformity of loading and so on – in the long term, it is not profitable. And as soon as it becomes obvious, in mushroom America, the race for reconstruction will begin. And maybe it has already started, simply no one wants to encourage competitors, pushing them ahead of themselves. 

Maksym Yenchenko, 

UMDIS Mushroom Information Agency 

AMYCEL representative in North-Eastern Europe  

The Mushroom Information Agency UMDIS advises on cultivation technology, investment, and features of the mushroom market. Contact: or +38 093 569 09 41 JTNDaWZyYW1lJTIwd2lkdGglM0QlMjI1NjAlMjIlMjBoZWlnaHQlM0QlMjIzMTUlMjIlMjBzcmMlM0QlMjJodHRwcyUzQSUyRiUyRnd3dy55b3V0dWJlLmNvbSUyRmVtYmVkJTJGZUlJWlAtX1dHMmclMjIlMjB0aXRsZSUzRCUyMllvdVR1YmUlMjB2aWRlbyUyMHBsYXllciUyMiUyMGZyYW1lYm9yZGVyJTNEJTIyMCUyMiUyMGFsbG93JTNEJTIyYWNjZWxlcm9tZXRlciUzQiUyMGF1dG9wbGF5JTNCJTIwY2xpcGJvYXJkLXdyaXRlJTNCJTIwZW5jcnlwdGVkLW1lZGlhJTNCJTIwZ3lyb3Njb3BlJTNCJTIwcGljdHVyZS1pbi1waWN0dXJlJTIyJTIwYWxsb3dmdWxsc2NyZWVuJTNFJTNDJTJGaWZyYW1lJTNF

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