Cultivating mushrooms in greenhouses

It is remarkable how every year mushrooms and fungi in general are gaining more and more followers thanks to their versatility, diversity, peculiar flavour, textures, colours and the multiple benefits they have for the balanced diet of human beings. Therefore, we want to dedicate this publication to the cultivation of mushrooms in greenhouses, their production and other data that can be especially useful if you are considering their cultivation or even if you are already involved in it.

Before we get into the subject, it is necessary to specify that, although mushrooms can be perfectly planted with the use of greenhouses, certain measures must be considered to guarantee that the final product has the necessary quality and is suitable for human consumption, since this is a crop that requires special attention due to its physiological characteristics and agronomical requirements.

Agricultural producers who have been working for years cultivating mushrooms in greenhouses know that, compared to other crops that require a certain amount of light, plenty of water and a significant land extension, mushrooms don’t need the incidence of sunlight to thrive, as they require areas where darkness and freshness are prevalent.

In that regard, it is important to note that the plastic films used for the greenhouse should be 100% opaque. Also, if the film can be bicolour (white/green for example) is even better since it becomes an additional factor for reducing the visual impact on the environment when the green face of the plastic is placed on the outside, so it mimics the environment of the field.

On the other hand, having a large planting surface is not necessary and depending on the type of farm and the amount of mushrooms you want to harvest, it is enough to have a specific area of the greenhouse that is shaded and not necessarily large to be able to plant the seeds.

How to cultivate mushrooms

This is one of the most frequently asked questions of both farmers and enthusiasts. The truth is that there are several alternatives that can be put into practice; however, some of the most popular are the use of tree trunks or trays that can be purchased already prepared or that have simply been manufactured with residues of other reusable materials.

If the idea is to use trays, it is recommended that they are at least 2 feet long and between 10 and 12 inches deep, so the raw material can be better distributed, and they are more likely to thrive in a suitable space.

On the other hand, if the trunks are preferred, those should be approximately 4 to 6 inches in diameter and at least 40 inches long, aside from preferring those coming from oak trees or other hardwood trees such as poplars, sugar maple, argan wood, yellow birch and alder, species that are harvested in late winter or early spring season.

If you use trays, those should be ideally filled with growing medium and then you can place the mushroom spawn on it, but in the case of tree trunks you must open some holes and fill them with mushroom spawn. The mushroom spawn will depend on the growing method selected and can be chosen from several types, where two of the most commonly used are brick and flake.

Considerations for the growing environment

Another crucial aspect is the culture medium, as it must be adequate to guarantee the quality of the final product.

It is recommended to cultivate mushrooms in a favourable environment based on a culture medium formed by organic materials containing a large amount of natural sugars and nitrogen, such as the one obtained by mixing straw with manure for example. Its properties related to humidity and nutrient content create the perfect setting for fungal growth.

There are agricultural producers who prefer to make their own compost, which is quite possible, since it can be created from the mixture of straw, peat, corn fodder and water, but it will depend on the amount of mushrooms you wish to sow. If the quantity is larger there are other alternatives such as, for example, purchasing mushroom kits that already have the culture medium and the mushroom spawn, so you can obtain the results you expect.

While it is ideal to have a space where darkness predominates, a minimal incidence of sunlight shouldn’t represent a significant damage when it comes to cultivating mushrooms in greenhouses. However, you have to be careful if you don’t have an area that is completely dark, making sure the amount of light is minimal and keeping pests away and under control to avoid compromising the integrity of the crop.

It is also important that the temperature inside the greenhouse remains stable, approximately between 55 and 60 degrees Fahrenheit, while the air should remain moist, trying to take additional measures to prevent the entry of strong air currents that can be harmful to the whole crop. In this sense, it is particularly important to inform the plastic manufacturer of the plastic film about the specific needs of the crop to obtain the most suitable one for the greenhouse.

Some plastic manufacturers that can customize their agricultural plastics to suit the farmer’s requirements, since they offer opaque plastics are:

• Reyenvas
• Solplast
• Sotrafa

Regarding this topic, we invite you to read our post on the critical temperatures of crops where we talk about the different types of plants, their ideal temperature to thrive and some recommendations about plastic films.

Steps to consider when cultivating mushrooms

The most important thing to do when it comes to cultivating mushrooms in greenhouses is to follow a few simple steps. First, prepare the growth beds so that you can spread evenly about 2 inches of soil, preferably dark and with a high content of nutrients, in the bed intended for cultivation.

The substrate to be used must be fully sterilized, so you can place it in a pressure cooker to guarantee that there are no contaminating agents in order to achieve this. The following step is to pour the substrate into the planting site and inoculate the same using fungus spores while adjusting the temperature according to the type of fungus you are sowing, this is crucial to maintain the humidity levels required by each species.

You should supervise permanently to notice when outbreaks occur, which can take place within three weeks, and at this time cover the growth area with a white mycelium network and increase the temperature in the greenhouse between 65 to 70 degrees Fahrenheit.

Spray the trays or tree trunks at least once or twice a day to keep the seeds moist and, once the mycelium is formed, lower the temperature to 60 degrees Fahrenheit and place a damp newspaper or a small layer of soil. You will probably be able to harvest the mushrooms after a month.

You can spray the compost twice a day to continue taking advantage of it to obtain new growths. No new sprouts will appear once the nutrients are depleted.

One of the aspects that cannot be overlooked when developing mushroom cultivation in greenhouses is to guarantee that there is an adequate fruiting condition, in other words, to guarantee a perfect combination of temperature, humidity and air intake to prevent the fungus from getting dehydrated without bearing fruit. Although it may seem simple this can be a challenge due to the characteristics and requirements of each type of mushroom, for this it is essential to be clever and know how to customize the conditions within the greenhouse.

Mushroom production in the United States

There are many varieties of mushrooms that can be cultivated today, whether it is for culinary or medicinal use; however, within the 2,000 species of edible mushrooms there are some that stand out and that have become the favourites in terms of consumption in the United States.

The most popular are the white button or agaricus mushrooms, as well as the criminis and portobellos, better known as brown mushrooms. There are also the shiitake that are being widely used in gourmet dishes, and the oyster, wood ears and enoki mushrooms.

According to information published on the website of the Agricultural Marketing Resource Center, in 2016 alone the United States produced a total of 943 million pounds of mushrooms, just slightly below the previous season, with a total crop value close to $1.2 billion for that year.

Most commercially produced mushrooms are from the agaricus species, showing that “out of the 919 million pounds of agaricus produced in 2016, the majority or at least 824 million pounds, were cultivated for the fresh produce market and 95 million pounds were processed.”

American consumers continue to buy fresh, canned and dried mushrooms, both domestic and imported. The cost of fresh mushrooms usually rises at the winter season, so many farmers rely on the cultivation of mushrooms in greenhouses to be able to produce mushrooms to meet the demand and as a way to increase production during the cold season.

A curious fact about mushroom production in the United States is that Chester County, in the State of Pennsylvania, has become the nation’s leading producer of fresh mushrooms, supplying nearly 50% of the country’s production. According to data published by Modern Farmer, the 61 farms that exist in this county are responsible for more than 400 million pounds of mushrooms valued at $365 million, contributing an estimated $2.7 billion to the local economy.

This industry is responsible for generating jobs for more than 10 thousand workers in the area, mostly from the Hispanic community. California ranks second with 18% of the production in the United States.