Grow Your Own Mushrooms: A Step-By-Step Guide

Mushrooms are a type of fungus, and not plants, and are more closely related to humans than plants. They are the fruiting bodies of fungi, thriving on substrates rich in organic material. They require an even, warm temperature, as well as moisture once they have spawned. Mushrooms can be grown indoors, in a bucket or on a log, or outdoors in your backyard. They grow best in cool, humid conditions, but can also be grown in more arid climates with more frequent watering. You can buy mushroom growing kits, which include a mushroom block filled with oat bran, sawdust or other substrate material that has been coated with mushroom spores. Alternatively, you can grow mushrooms from scratch by purchasing mushroom spawn or spores and growing them in a suitable substrate.

Using a growing kit

Using a mushroom-growing kit is a straightforward way to start cultivating mushrooms. These kits are dispatched when fully colonised and ready for fruiting. They require little maintenance and can be set up indoors.

To begin, you should always wash your hands before working with a grow kit. It is recommended to start growing as soon as you receive your kit, although it is possible to delay for weeks or even months if kept refrigerated. When you are ready, bring the kit to room temperature.

The next step is to identify the type of mushroom you are growing and the specific requirements for that species. The method for opening the kit will depend on whether the mushroom is side-fruiting or top-fruiting. For side-fruiting varieties, such as lion's mane and oyster mushrooms, make a small cut into the grow bag to expose the substrate to fresh air. Tape can be used to hold the bag against the substrate. For top-fruiting varieties, such as king oyster and reishi, open the top of the bag and fold it over with a clip to restrict airflow.

Once the kit is prepared, it is important to provide the right growing conditions. Mushrooms require high humidity to form, so a humidity tent or a misting and fanning regime can be used to maintain the correct moisture levels. Alternatively, a humidifier and humidity controller can be used to automate the process. Fresh air exchange is also important, as mushrooms produce carbon dioxide and will grow long and leggy if they require more oxygen.

Finally, when the mushrooms are ready, it is time to harvest them. It is important to do this before the veils under the caps tear, as this will impact future flushes. To harvest, grab the base of the stalk and gently twist and pull the mushroom away. After picking, the stems may turn bluish, which is called 'bruising' and is evidence of potency.

Choosing a substrate

Mushrooms require a substrate rich in organic material to provide them with the right mix of nutrients, including sugar, starch, lignin, fats, protein, and nitrogen. There are various options for substrates, each with its own level of complexity. Some mushrooms thrive better on specific substrates, so it is essential to research the ideal conditions for the mushroom type you want to cultivate. Here are some commonly used substrates:

• Compost: Mixing spawn with compost is a simple method that allows nature to take its course.
• Straw: Straw is a suitable substrate for mushroom growth, but it may need to be pasteurized to eliminate any contaminants.
• Sawdust: Sawdust is another option, but it is important to ensure it is free from contaminants by pasteurizing it before use. Hardwood sawdust is commonly used.
• Coffee Grounds: Coffee grounds can be used as a substrate to grow mushrooms.
• Wood Chips: Wood chips can be soaked in boiling water, drained, and then layered with spawn in a bucket to create a suitable environment for mushroom growth.
• Soil: A layer of potting soil can be used to cover the mixture of spawn and substrate, providing the necessary nutrients for mushroom growth.
• Oats: Oat bran is often included in mushroom-growing kits as a substrate material coated with mushroom spores.

When choosing a substrate, it is important to consider the specific requirements of the mushroom variety you plan to cultivate, as each species has unique preferences for its growing environment.

Preparing the spawn

Preparing spawn is a critical step in mushroom cultivation. It involves creating a medium for the mushroom mycelium to grow and colonise before being transferred to the substrate. Here is a detailed guide on preparing the spawn:

Selecting Spawn Substrate

The first step is to choose the right substrate for the spawn. Grain spawn is the most common and effective option for mushroom cultivation. Various grains can be used, such as rye, wheat, millet, or a mix of these grains. These grains provide an ideal environment for mycelium growth due to their nutritional content and ability to retain moisture.

Sterilising the Substrate

Sterilisation is a crucial step to ensure a contaminant-free environment for the mycelium to thrive. Place the chosen grain in a pressure cooker or autoclave, ensuring it is fully submerged in water. Follow recommended timing and pressure settings for grain sterilisation, typically around 15-20 PSI for 1-2 hours. This process eliminates any potential contaminants, ensuring a healthy spawn.

Inoculating the Spawn

After sterilisation, allow the grain to cool in the closed pressure cooker. Once cooled, carefully open the cooker and check for any signs of contamination, such as discolouration or unusual odours. If the grain appears healthy, proceed to the inoculation. Wear a face mask and sterile gloves to maintain a sterile environment. Using sterile technique, transfer a small amount of grain to a petri dish or spawn bag. Then, introduce the mushroom spawn or culture syringe, containing the desired mushroom mycelium, into the grain. Mix gently to distribute the mycelium evenly.

Incubation and Colonisation

Place the inoculated spawn in a warm, dark location with a temperature range of 21-29°C. This temperature range accelerates mycelium growth. Maintain a slightly moist environment by misting the spawn with sterilised water if needed. Over time, the mycelium will colonise the grain, turning it into a white, fluffy mass. This process typically takes 2-4 weeks, depending on the mushroom species and environmental conditions.

Expansion and Maintenance

Once the grain spawn is fully colonised, it can be used to inoculate the substrate or expanded to create more spawn. To expand, simply introduce a small amount of the colonised spawn to a new batch of sterilised grain, following the same sterile techniques. Continue this process to build up a substantial amount of spawn for larger cultivation projects.

Preparing spawn is a delicate and patient process. It requires attention to detail, sterile techniques, and a controlled environment to ensure the success of your mushroom cultivation endeavours.

Maintaining temperature and moisture

Maintaining the right temperature and moisture levels is crucial for successful mushroom cultivation. Mushrooms are delicate and temperamental crops that require specific conditions to thrive. The ideal temperature and humidity ranges vary depending on the mushroom species, so it is important to tailor the growing environment to the specific needs of the mushrooms you wish to cultivate.

Temperature control is essential during all stages of mushroom growth. The optimal temperature range for most mushroom cultivars is between 23°C to 26°C (73.4°F to 78.8°F). However, some sources suggest a slightly wider range of 60°F to 70°F (15°C to 21°C). Maintaining a consistent temperature is crucial, as even small fluctuations can impact the growth rate and quality of the mushrooms. During the incubation stage, which typically lasts two to three weeks, the temperature should be maintained between 65°F to 75°F (18°C to 24°C). This stage is critical for the formation of the mycelium, the vegetative part of the mushroom. Once the mycelium has formed, the temperature needs to be lowered to around 50°F to 60°F (10°C to 16°C) during the fruiting stage to encourage the growth of the fruiting bodies.

To control temperature levels, you can use heating and cooling equipment such as heating pads and cooling fans. Additionally, it is important to provide adequate ventilation and diligent temperature monitoring to ensure ideal conditions for mushroom growth.

Maintaining high humidity levels is also crucial for mushroom development. Relative humidity should be maintained between 80% and 95% to create an optimal environment for mushrooms. High humidity helps retain moisture, which is vital for the opening of mushroom caps and the overall health of the fruiting bodies. When a bag is first placed into a fruiting chamber, a slightly higher humidity of up to 95% is recommended for the initial development of pins (tiny mushroom heads). After a day or two, the humidity should be adjusted to approximately 80%. A higher relative humidity results in faster mushroom growth, while lower humidity levels can lead to slower-growing but more flavorful mushrooms.

To regulate humidity, growers can use humidifiers, misting systems, humidity domes, and spray bottles. Fans can also be used to distribute moisture evenly and reduce the risk of mould. It is important to ensure that the growing containers are made of materials that can hold moisture, such as plastic, glass, or polyethylene bags. Additionally, the containers should be large enough to allow for proper air circulation, which is crucial for maintaining humidity levels.

Harvesting

For the first flush, it is common to see miniature-sized mushrooms, which is normal and not a cause for concern. To make harvesting easier, you can float your cake on top of filtered water, which also helps to rehydrate the cake and access any bottom or side pins.

When it comes to harvesting oyster mushrooms, the ideal time is indicated by the shape of their caps rather than their size. It is best to harvest when the caps begin to uncurl and flatten but before they become too flat. The edges should still be slightly curled under to limit the number of spores released.

For pink oyster mushrooms, in particular, they should be harvested before they release pink dust. You can harvest them before the caps start to flatten, especially if they have already reached a good size. Younger mushrooms tend to be more tender and succulent.

Shiitake mushrooms can be harvested when the edges of the caps are curled under, and 80% of the gills are exposed. You can also check if the partial veil has broken, exposing the gills.

When harvesting, you can either twist and pull the mushrooms or slice them, leaving stumps. Twisting and pulling can disrupt and damage the network of mycelium, so it is recommended to use scissors for larger clumps to harvest them as close to the surface as possible.

It is important to note that if mushrooms are left to mature too long, they will drop spores. While this is not a significant issue, it can make it harder to get subsequent flushes from the same area.

Frequently asked questions