Growing mushrooms in greenhouses

Mushrooms are grown for various purposes, including for eating. In fact, their consumption is on the rise: not only are they tasty, they are also healthy as they are rich in protein and other nutrients, low in fat, and low in calories.

In Italy, the most commonly grown mushrooms are the field mushroom or champignon in its many varieties (Agaricus bisporus) and Pleurotus ostreatus (known as oyster mushroom, pearl mushroom, hiratake, etc.). Other species include the king oyster or king trumpet mushroom (Pleurotus eryngii), the poplar fieldcap or velvet pioppini (Cyclocybe cylindracea or aegerita), and the shiitake mushroom (Lentinula edodes). You don’t need to buy them at the supermarket as these are all types of mushrooms that you can also grow at home. Today, we will give you an overview of how to grow edible mushrooms yourself.

Mushroom cultivation: how it works

Mushrooms are not grown on regular soil but on special growing substrates, from which they absorb nutrients. These are mixtures of organic and mineral materials, packaged in blocks with plastic wrappings (grow bags), produced by companies specializing in the preparation of substrates for mushroom cultivation. The substrate varies according to the species of mushroom to be grown, ensuring optimal chemical, physical, and nutritional conditions. The raw materials for the substrate are usually controlled waste from agricultural and industrial activities, such as various types of straw and wood processing residues. The substrate also undergoes heat treatment (pasteurization) to kill pathogens and fungi that compete with the species to be cultivated.

The substrate grow bags you buy (in agricultural stores, nurseries, online, etc.) may be pre-inoculated or already incubated with a specific type of mushroom. What does that mean? Inoculation or sowing consists of mixing the mycelium—i.e., the “seed” of the mushroom—into the substrate, usually in the form of grain seeds or sawdust/wood chips on which the mycelium itself has developed (spawn). Inoculation is followed by incubation, the phase in which the mycelium colonizes the substrate. At the end of incubation, the mushroom grow bag is ready for production. The substrate blocks should come with cultivation instructions, which we recommend you follow step by step.

Growing mushrooms yourself: the mushroom greenhouse

Growing mushrooms requires fairly large spaces: the ideal solution is to build a special structure, a mushroom greenhouse. Mushroom greenhouses for professional mushroom cultivation are mechanized and technologically sophisticated. They are equipped with heating/cooling, humidification, and ventilation systems for air recirculation; artificial light; and computerized management of environmental parameters, which are monitored by sensors.

In fact, in order to fruit and grow, mushrooms need the right temperature, humidity, light, and the correct concentration of oxygen and carbon dioxide in the air. These environmental parameters vary depending on the type of mushroom and the stage of cultivation: incubation (if this takes place in a mushroom farm), fruiting (from the end of incubation to the appearance of small mushrooms), ripening, and harvesting.

As a rule, the production, and therefore the harvesting, of mushrooms takes place in several waves (flushes), which become progressively less plentiful, after which the cultivation substrate has exhausted its available nutrients. At this point, you can mix it with soil to obtain compost for garden and vegetable plants, use it as mulch, or compost it. Depending on the species, mushrooms grow on the top of the substrate grow bag, which is uncovered, or from cuts you make on the sides of the wrapping. We recommend that you follow the cultivation instructions each time. And that’s not all: if you want to grow mushrooms, we suggest you study the biology and specific needs of the species you are interested in.

For DIY mushroom cultivation, you can adapt existing environments, such as your basement or garage, or build a mushroom greenhouse. A mushroom greenhouse is a tunnel structure supported by arches made of curved iron pipes and protected from the outside with a covering.

It can be covered, for example, with corrugated fiberglass or opaque polycarbonate sheets (so that no direct light enters the greenhouse) or with thick shade cloth combined with plastic greenhouse sheeting, which protects from rain and retains moisture and heat inside (in cold weather). The ends of the tunnel are closed in a similar way: make sure there is enough space to transport the mushroom grow bags into the mushroom bed, for example with a wheelbarrow or transporter. Once opened and protected with shade cloth to keep out insects and other pests, the entrance also serves to ventilate the greenhouse. Always keep the area around the mushroom greenhouse clean by cutting back vegetation, for example using a brushcutter, wheeled brushcutter, or flail mower.

The mushroom greenhouse floor may be paved with concrete or simply covered with mulch. Depending on the species, you can grow mushrooms by burying the grow bags in the ground or by keeping them raised on shelves or small platforms (e.g., fruit crates). The construction of the mushroom greenhouse should be designed according to the climate in your area. In any case, while building the tunnel, you may find it useful to have a power generator to run the necessary equipment, if you need to weld the metal support structure or carry out other work.

In the mushroom greenhouse, cultivation involves ensuring that humidity, temperature, light, and ventilation are adequate for the different stages of cultivation. Therefore, check the humidity and temperature by placing thermometers with built-in hygrometers at several points in the tunnel. Once or several times a day, depending on the humidity, spray water on the mushroom grown bags with a backpack sprayer or, if you only have a few, with a pressure pump or a standard spray bottle. When working on the mushroom grow bags, harvesting, etc., your hands and clothes must be clean. In fact, all the equipment you use must be disinfected, for example with bleach.

Other ways to grow mushrooms at home

In addition to mushroom greenhouses, there are several other ways to grow mushrooms yourself. At home, you can literally grow them with special kits that are easy to use even if you are not an expert (just follow the instructions provided). Ready-to-use kits are available on the market, already seeded and incubated: just place the mushroom grow bag in a humid and bright environment and spray it with water when needed. Other kits contain everything you need to grow mushrooms from scratch, preparing the substrate yourself, sowing the mycelium, waiting for the incubation period, and so on.

Alternatively, you can grow mushrooms in your garden, finding a shaded and humid area, such as under trees. Outdoors, you can grow mushrooms in various ways, using secondary areas of the garden or areas unsuitable for vegetable growing:

• On logs or stumps inoculated with mycelium spawn plugs (dowels), i.e., small wooden cylinders colonized by the mushroom mycelium that are inserted into the wood. Slices of trunk stacked on top of each other and inoculated with sawdust spawn can also be used.

• In various containers (fruit crates, plastic pots, etc.) that are clean and filled with straw or sawdust as a substrate, which must be inoculated with sawdust spawn, generally more suitable for outdoor environments than grain spawn.

• On the ground, in an area free of grass, where you layer the growing substrate and mycelium in the form of sawdust spawn.

• As live mulch in vegetable gardens or flower beds, where you spread sawdust spawn mixed with straw or sawdust, covering everything with a protective layer of straw or cardboard to enrich the soil with organic matter and promote its biodiversity.

If you choose to grow mushrooms on sections or slices of log, the wood must be fresh—recently cut with a chainsaw—and healthy.

Growing mushrooms at home can be an alternative or a complement to traditional vegetable gardening. In any case, it is an interesting resource for growing your own food. Here are some other articles related to this topic: how to raise snails, how to build a DIY beehive for raising bees, and a DIY barn for goats or sheep.