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How to Grow Mushrooms Indoors: A Beginner’s Guide

Mushroom growing can be a rewarding hobby with benefits that extend beyond the taste and nutritional value of your crop. But there are some important concepts that you must understand before getting started.

Mushrooms grow from a white mass of mycelium, which colonizes the substrate and prepares it for fruiting. To speed up this process, it is important to incubate your substrate at a warm temperature.


Mushroom cultivation is a DIY hobby that requires a lot of patience and care. The process involves buying mushroom spawn, preparing and inoculating the substrate, and creating fruiting blocks. Using grow kits makes the project easier for beginners, but you can also make your own substrate and inoculation mixtures.

The Latin prefix sub- means “below” or “under.” In the case of a mushroom substrate, the idea is that the fungus will spread from the grain spawn to cover and colonize the entire container or tray. This process, called colonization, takes a few weeks.

When the substrate is inoculated, it’s placed in a dark and cool place for a few weeks, so the mushroom mycelium can grow throughout it. The container or tray should be kept away from sunlight to give the mushrooms their optimum temperature of around 21 degrees Celsius. A plastic bag may be used to keep the soil or spore mixture moist, but it should not be sealed tightly — mycelium needs airflow to develop.

The substrate can be made from a mix of compost, vermiculite, or even sawdust, depending on the type of mushroom you’re growing. Some species, such as shiitakes, grow best on hardwood sawdust logs. Others, like oyster mushrooms, thrive in straw or cotton hay. The spawn is then mixed into the substrate and covered with a layer of newspaper. After several weeks, white thread-like mycelium should appear.

Once the spawn and substrate are fully colonized, you can remove the paper and mist the surface to trigger fruiting. To do so, you should first make sure that your environment is sterile and that there are no other microorganisms present that might compete with the mushroom mycelium for water or nutrients. This is achieved by cleaning surfaces and tools, wiping containers with isopropyl alcohol, and pasteurizing or sterilizing the substrate.

Once the mushrooms are growing, you’ll need to maintain these conditions, and harvest them when their caps have fully opened. Mushrooms grow quickly, and can double their size within a day or two once they’ve reached maturity.


Mushroom cultivation requires a lot of attention to detail, especially in a home setting where the conditions can be quite variable. The first step is to determine the mushroom species you would like to grow and then source the appropriate substrate and spawn. Oyster mushrooms (Pleurotus ostreatus) are the most popular species to grow at home as they can be grown on straw, sawdust blocks, coffee grounds and cardboard. They also grow very quickly and are hardy.

Once you have your substrate ready and sterilized (this is done using a pressure cooker or cooking pot), inoculation can begin. Spawn is live fungal culture that is injected into the substrate to initiate a mushroom colony. The simplest method is to use a PF tek or a similar technique. The idea is to inject the spores into the substrate through a small syringe and then cover the container with a layer of vermiculite, a coarse material that allows the spores to settle on it. Then, the substrate is placed in a dark place and allowed to incubate.

During this time the mushroom spores germinate and develop into mycelium, which is what grows the mushrooms. As this process takes place, the spores will absorb some of the substrate’s nutrients and carbon dioxide. During this stage it is important to make sure that the temperature of the room does not get too warm or mycelium will die and your mushrooms will not grow, so it is advisable to use special shrooms monotub for this.

When the mycelium is sufficiently developed, the syringe can be removed and the substrate lightly misted to keep it moist. At this point, the mushroom spores will be covered by a white layer of mycelium that looks like a dusting on the surface of the soil. The substrate should be kept in a cool, dark place at about 21 degrees Celsius. A light heat source can be used if necessary, but no direct sunlight, as this will burn the spores.

Mushrooms require a good amount of oxygen to grow. If there is not enough oxygen in the growing medium, mushrooms will appear deformed, spindly or wrinkly. A tent like enclosure can be used to keep the air moving and nutrient levels high, but the space should not be sealed too tightly. Oxygen-starved mushrooms will also lose a lot of water, so the enclosure should be opened often to let in fresh air.


Mushrooms have become increasingly popular as a DIY pursuit. From picking and foraging to growing them at home, mushrooms are fun to grow, offer a unique culinary experience and are believed to have some health benefits. Growing mushrooms at home requires a little more effort than some other crops, but the basic principles are fairly easy to master. Growing mushrooms indoors requires a space that moderates temperature, humidity and light to mimic the environmental conditions of the wild and encourage spore production. This can be as simple as a closet, a garage or basement to a retrofitted room or a building designed for mushroom cultivation.

Mushroom growth relies on a substrate made up of decaying organic matter such as wood chips, sawdust or straw to provide the nutrients necessary for colonization. This is known as the spawn bed or casing layer. To cultivate mushrooms, the bed must be inoculated with a mushroom spawn that is recommended for your climate. The spawn should be spread over the substrate and covered with 2.5cm (1″) of a mix of 50% garden soil or compost, 50% peat and a handful of lime (to make the soil more alkaline). The compost must be tightly packed to keep it from washing out. Once colonized, the casing should be kept moist by misting with water using a rose watering can or a spray bottle.

The mushroom spawn can be purchased in a kit that includes the pre-inoculated substrate, called a grow log, or you can buy a bag of spores and inoculate your own logs. Regardless of the method, it can take several months to up to a year to harvest your first crop of mushrooms from a log-growing method.

If you decide to try this method, Lynch recommends beginning with oyster mushrooms, which are easier than some other varieties, such as shiitake, pioppino or lion’s mane. Oysters grow well on many substrates, including coffee grounds, cardboard and cornstalks. They are also hardy and tolerate a wider range of temperatures than some other varieties. Aside from finding the right type of mushroom, the key to success with a log-growing mushroom is providing adequate oxygen. Mushrooms that are starved for oxygen may rot before they produce fruit.


While many gardeners are adept at growing vegetables, fungi require a different skill set than plants. Mushrooms like cool, damp, dark conditions. While some species, such as morels and truffles, are best off foraged, there is a wide variety of edible mushrooms that can be grown easily indoors in a small grow space.

The simplest way to cultivate mushrooms is to buy pre-poured agar, a nutrient-rich gel that serves as a substrate for germinating spores. This can be purchased at most nurseries and some grocers. For a more hands-on approach, you can make your own agar at home by cooking it on the stove in a water bath. Some spores, such as oyster mushroom spores, are quite hardy and will germinate with very little heat, while others are more finicky and need to be cooked in a special mixture of water and nutrient-rich glycerol.

Once the agar has been prepared, it can be spread on a surface that is not in direct sunlight and covered with a layer of newspaper for a few days until white thread-like mycelium appears. Once this has happened, the agar can be covered with a layer of compost or soil that is 50 per cent organic matter and 50 per cent lime. Keep the surface moist by misting regularly or using a hose with spray attachment. After several weeks, if you have the right conditions (temperature and humidity), you should begin to see mushroom pins appearing.

These will first appear as a white coating on the surface of the mycelium and then will begin to grow, or “fruit,” into adult mushrooms within a week or two. They will continue to double in size daily until they are ready for harvesting.

One of the most difficult aspects of growing mushrooms is meeting all the specific conditions that a particular species requires. It is important to research the type of mushrooms you are trying to cultivate so that you have an understanding of their needs and can provide them with the proper conditions. This will help ensure success and a successful crop of mushrooms.

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