Mushroom Magic: Understanding Sawdust Spawn Power

Mushroom sawdust spawn is a popular method for cultivating mushrooms, favoured for its ease of use, low cost, and good results. It is a great choice for beginners as it is relatively simple to work with and produces satisfactory outcomes. Sawdust spawn is created by inoculating sawdust with live mycelium, which then colonizes the substrate. The substrate is typically hardwood sawdust, such as oak, beech, or maple, mixed with supplements like bran, soybean hulls, or coffee grounds. This mixture is then sterilized and cooled before introducing the mushroom spawn. The spawn rate can be adjusted to speed up colonization and reduce the risk of contamination. The inoculated sawdust block is then sealed and placed in a warm, dark area for incubation. As the mushroom spawn spreads and feeds on the organic material, the mycelium grows, leading to the formation of mushrooms.

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The inoculation process: Drill holes into logs, fill with spawn, and seal

The inoculation process involves drilling holes into logs, filling them with spawn, and sealing them. This method is ideal for outdoor use and inoculating large quantities of logs or mushroom growing beds. Before you begin, ensure your work surfaces are clean and your hands are washed to avoid contamination.

Drill holes into the logs using a drill or angle grinder with an adapter and a special drill bit. The depth and width of the holes will depend on the size of the log and the amount of spawn you have. As a general rule, the holes should be deep enough to accommodate the spawn without overflowing.

Next, fill the holes with sawdust spawn, ensuring the spawn is evenly distributed and well-packed. The spawn should be at room temperature and free of any contaminants. Once the holes are filled, use wax to seal the holes and secure the spawn in place. The wax will also help to prevent contamination and moisture loss.

After sealing, the inoculated logs need to be incubated. Place them in a dark, warm area with temperatures ranging from 65 to 77 degrees Fahrenheit (18 to 25 degrees Celsius). The logs should be left undisturbed for several weeks to allow the spawn to spread and colonize the substrate. During this time, check the logs periodically for any signs of contamination, such as discolouration or unusual odours.

Once the substrate is fully colonized, it can be used to grow mushrooms. This process, known as "colonization," can vary in duration depending on the mushroom species and environmental conditions. However, you should eventually see fine, white mycelium forming on the substrate, indicating that it is ready for mushroom cultivation.

Sterilisation: Kills unwanted bacteria and fungi

Sterilisation is a crucial step in the process of mushroom cultivation to prevent contamination and ensure successful mushroom growth. The goal of sterilisation is to kill any unwanted bacteria or fungi that may compete with or hinder the growth of the desired mushroom spawn.

Before sterilisation, it is essential to prepare the substrate by mixing hardwood sawdust with chosen supplements. A commonly recommended ratio is 5 parts sawdust to 1 part bran, creating a moist but not dripping wet mixture. This substrate is then packed into bags or containers, leaving enough space for mushroom growth and ensuring even distribution without compacting the mixture.

The bags or containers are then sealed and subjected to sterilisation. A pressure cooker or autoclave set at 15 psi for 90 minutes is typically sufficient to kill unwanted microorganisms. However, it is important to note that the time required may vary depending on the mass loaded into the steriliser. For example, a typical load of 18-20kg of substrate would require at least 3 hours.

After sterilisation, it is crucial to allow the substrate to cool to room temperature in a clean area to prevent contamination. This cooling period ensures that the high temperatures used during sterilisation do not inadvertently kill the desired mushroom spawn when it is introduced.

By following these steps and paying close attention to the sterilisation process, mushroom cultivators can effectively kill unwanted bacteria and fungi, creating an optimal environment for their desired mushroom species to thrive.

Humidity and temperature: Affect colonisation time and success

Humidity and temperature play a crucial role in the colonisation time and success of mushroom sawdust spawn. Mushrooms thrive in humid conditions, with optimal humidity levels for growth ranging from 85% to 95%. Maintaining the desired humidity can be achieved through misting the growing area, but care must be taken to avoid over-wetting the substrate. Additionally, ensuring proper air circulation is vital to prevent CO2 buildup, which can hinder mushroom development.

During the incubation phase, opinions vary on the necessity of humidity. Some sources claim that incubators should not be humid at all, as humidity can lead to bacterial contamination. In contrast, other sources suggest that humidity levels during incubation can range from 30% to 85% RH (relative humidity). However, it is generally agreed that higher temperatures during incubation can increase the likelihood of contamination.

When it comes to fruiting, mushrooms prefer slightly lower humidity levels, with a range of 60% to 85% being optimal. Shiitake mushrooms, for example, thrive in temperatures of 50–85 °F (10–29 °C) and 60% to 85% humidity. Maintaining the ideal humidity and temperature conditions for the specific mushroom variety is crucial for successful colonisation and fruiting.

The initial moisture content of the substrate is also important. It can be determined by measuring the moisture content of the sawdust before starting the process. The final moisture content should aim for around 60% of the total weight, as evaporation and the addition of supplements will affect the overall moisture level.

Additionally, the spawn to substrate ratio can influence colonisation time and success. Increasing the spawn ratio can speed up colonisation and reduce the risk of contamination. This is because more spawn leads to faster mycelial growth and a quicker transition to fruiting.

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Spawn to substrate ratio: A higher ratio reduces contamination risk

When cultivating mushrooms, it is crucial to understand the relationship between the spawn and the substrate. The spawn to substrate ratio plays a significant role in the success of mushroom cultivation, particularly in reducing the risk of contamination.

The spawn to substrate ratio refers to the proportion of mushroom spawn used relative to the amount of substrate or growing medium. A higher spawn to substrate ratio is often recommended to reduce the risk of contamination. This is because a higher ratio of spawn can lead to faster colonisation of the substrate by the mycelium. As a result, there is less opportunity for mould or bacteria to develop and contaminate the substrate.

For example, a 1:2 ratio of spawn to substrate is suggested for beginners by Curious Ape Mushrooms. This ratio provides a balance between fast colonisation and a reduced risk of contamination. On the other hand, a more advanced grower might opt for a 1:4 ratio, which uses less spawn and is more cost-effective, but it carries a higher risk of contamination and requires careful management.

It is worth noting that the spawn to substrate ratio can vary depending on the type of substrate being used. For instance, when using straw as a substrate, a spawn ratio of 1:20 is recommended, whereas for manure, compost, or coir substrates, a ratio no higher than 1:4 is advised.

To further minimise the risk of contamination, it is essential to maintain a sterile environment during the inoculation process. This includes cleaning work surfaces, hands, and equipment, as well as ensuring the substrate has cooled to an appropriate temperature before adding the spawn, as high temperatures can kill the mycelium.

Choosing spawn: Buy from a reputable, local company

When choosing mushroom sawdust spawn, it is important to buy from a reputable, local company. This is because the spawn should be as fresh as possible, and buying from a local company minimises the time it spends in transit. The spawn will weaken over time and its chances of success will decrease, so it is best to use it soon after it arrives. To extend the life of the spawn, you can store it in the fridge, but it will still become less viable the longer you wait.

It is also important to ensure that the spawn is of good quality and has been produced by a company with a good track record. Contamination is a common issue when growing mushrooms, and old or well-travelled spawn may be less likely to grow. Buying from a reputable company can help to reduce the risk of contamination and increase your chances of success.

In addition to buying from a reputable local company, it is a good idea to do your own research and choose the right type of spawn for the specific mushrooms you want to grow. The type of spawn you use can depend on various factors, such as whether you are growing mushrooms indoors or outdoors, and the type of substrate you are using. For example, sawdust spawn is typically used for outdoor growing and is ideal for inoculating large quantities of logs or mushroom growing beds. On the other hand, grain spawn is better for smaller substrates or fruiting blocks.

When choosing a local company, you may also want to consider the specific ingredients and processes they use. For instance, some companies use hardwood sawdust supplemented with soybean hulls, while others use a mixture of hardwood and softwood sawdust. You can also look for companies that offer guarantees, such as free replacements for any products that arrive damaged or contaminated. By doing your research and choosing a reputable, local company, you can increase your chances of success when growing mushrooms with sawdust spawn.

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