Laura Smith
Mushroom inoculation is the process of bringing spawn into contact with a food source to initiate its growth. The goal of inoculating is to introduce the mycelium culture to as many points in the substrate as possible, allowing the mycelium to quickly colonize the substrate before competing organisms take hold. The substrate is the medium that the mycelium will grow in, typically a natural waste product such as straw, wood chips, sawdust, or even paper. Before inoculating the substrate, it must be hydrated and sanitized. The inoculation rate, or the amount of spawn added to the substrate, will determine the speed of spawn run and the growth of mycelium. After the substrate has been inoculated, it is ready to be incubated in an environment with warmth and humidity.
How to Inoculate Mushroom Substrate
| Characteristics | Values |
|---|---|
| Purpose | To introduce the mycelium culture to as many points in the substrate as possible, so that the mycelium can quickly colonise the substrate before competing organisms get a chance to take hold. |
| Substrate | Straw, sawdust, woodchips, freshly cut hardwood logs, compost/manure, cardboard, paper, etc. |
| Preparation | Substrate must be hydrated and sanitised. For straw bags or sawdust blocks, the substrate must be pasteurised or sterilised using heat or alkalinity changes to prevent competing microbes. |
| Inoculation Methods | Drilling holes into a log, cutting wedges into a stump, mixing spawn into individual bags, using spore syringes, or spreading mycelium-coated materials/liquids (mushroom spawn) through the substrate. |
| Spawn Types | Grain spawn, sawdust spawn, liquid culture, or petri dish culture. |
| Environmental Conditions | For outdoor methods, there is little concern for introducing contaminants, while indoor methods require sterile conditions to avoid contaminating the substrate. |
| Incubation | Provide warmth and humidity to the mycelium while it colonises. Suitable temperatures range from 15-30°C, with mid-20s being optimal. |
| Fruiting | Once the substrate is fully colonised (visually observable by white mycelium), it is ready for fruiting. Provide indirect light and cut horizontal slits on the bag for airflow and mushroom growth. Maintain high humidity to prevent mushrooms from drying off. |
| Contamination | If there is mould, sprinkle salt directly on the mould or scoop it out with a sterile spoon. If mould is extensive, start over with a new spawn and substrate. |
| Notes | The inoculation rate is the amount of spawn added to the substrate, balancing colonisation speed and cost. Higher rates lead to faster mycelium growth but do not increase mushroom yield. |
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What You'll Learn
The importance of hydration and sterilisation
Hydration of the substrate is essential as it provides the necessary moisture for the mycelium to thrive and colonise the substrate effectively. However, it is crucial to achieve the right level of hydration, as too much or too little water can hinder the colonisation process and reduce yields. The substrate should be kept slightly on the drier side, as waterlogged substrates are more susceptible to contamination. A common method to determine the optimal hydration level is the squeeze test, where only a few drops of water should drip out when a handful of hydrated substrate is squeezed tightly.
Sterilisation of the substrate is another critical aspect of successful mushroom cultivation. It helps eliminate competing organisms and creates a clean environment for the desired mushroom culture to establish itself. Sterilisation methods can vary depending on the substrate type. For example, straw and woody substrates may require shredding and soaking before sterilisation, while coffee grounds may not need sterilisation if they are fresh and handled with proper hygiene.
The choice between dry and wet inoculation methods also influences the hydration level of the substrate. Dry inoculation involves using dry spawn, while wet inoculation introduces spawn mixed with water. The decision between the two methods depends on factors such as the mushroom species, the growth environment, and the stage of the mushroom cultivation process.
To ensure effective sterilisation, it is common to use techniques like pasteurisation or steam sterilisation, raising the pH level of the substrate, or employing equipment like a pressure cooker, a still air box, or a laminar flow hood. Sterilisation times and temperatures may vary, but it is crucial to allow the substrate to cool in clean conditions before inoculation to prevent contamination.
In summary, proper hydration and thorough sterilisation of the substrate are key factors in the inoculation process. These steps ensure that the mycelium has the optimal environment to colonise the substrate rapidly and produce a successful mushroom crop.
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Choosing the right substrate
The first thing to consider is the availability of a particular substrate. For example, straw-based substrates are more accessible than hardwood substrates and can be prepared using basic home utensils. You should select a substrate that is readily available in your area. If straw is not an option, sawdust or pre-inoculated pellets are good alternatives.
Next, you should consider the specific needs of the mushroom species you are growing. For instance, wood-based substrates are optimal for reishi, lion's mane, and maitake mushrooms, while oysters can grow on nearly any substrate. Shiitake mushrooms grow best on hardwood sawdust from oak and beech or from logs outdoors. Lion's mane mushrooms also grow well on hardwood sawdust, especially from oak, beech, or maple trees. If you are growing button mushrooms, a composted substrate mixed with straw and manure is ideal.
Another popular substrate combination is MASTER MIX, a 50-50 mix of sawdust and soybean husk. This mixture yields more than a traditional substrate, although it still requires sterilisation. Coffee grounds are another low-tech mushroom substrate option that does not require pasteurisation or sterilisation, as long as they are used quickly and handled with proper hygiene.
To achieve the right hydration for your substrate, it is important to conduct a squeeze test. Pick up a handful of the hydrated substrate and squeeze it as tightly as possible. Only a few drops of water should drip out; if there is more, you have added too much water. If there is no water, you will need to add more.
Before inoculating the substrate with spawn, it is important to sterilise it to kill off any competing mould or bacteria. Sterilisation techniques such as heat pasteurisation or chemical sterilisation can help to eliminate competing organisms.
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The role of incubation
Incubation is a crucial step in the mushroom cultivation process, during which the mycelium is left to grow, spread, and colonise the substrate. It begins right after inoculation and ends when the substrate has been fully colonised, preceding the fruiting stage. While incubation is mostly a hands-off phase, growers play a vital role in providing optimal conditions for mycelium growth and development.
The primary role of growers during incubation is to maintain an environment with the right temperature and humidity levels. Most mushroom species thrive in temperatures ranging from 15°C to 30°C, with mid-20s being the optimal range. A high humidity environment is also essential to prevent the mushrooms from drying out or becoming stunted during growth.
The duration of incubation varies depending on the mushroom variety and the substrate used. While some species like oysters can colonise a substrate in just 2-3 weeks, others like Reishi can take months. Logs, for instance, typically require at least six months to a year of incubation, whereas nutrient-rich substrates like straw or sawdust can be colonised by mycelium in 10 to 14 days.
To optimise incubation, growers should monitor the development of their mushroom blocks. This includes checking the growth rate and ensuring even mycelial growth. If the mycelium is growing slowly, issues with the culture or environmental conditions may be the cause. In some cases, growers may need to intervene by triggering the fruiting process, such as by rehydrating the substrate or using temperature changes for certain mushroom species.
Additionally, growers should be mindful of potential contaminants during incubation. For example, fungus gnats can access and feed on the mycelium if the incubation area is not well-contained. Therefore, ensuring that containers are well-sealed is crucial to prevent contamination and promote successful colonisation during incubation.
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Inoculation rates
The inoculation rate is the amount of mushroom spawn or liquid culture added to a substrate. It is usually shown as a ratio to the amount of substrate. The ideal inoculation rate balances colonisation speed and the cost of spawn per pound or kilogram of mushroom yield. The higher the spawn rate, the faster the mycelium will colonise the substrate, but generally, a higher yield is not achieved. Growers aim to use as little spawn as possible while not drastically increasing colonisation time or chances of contamination.
The inoculation rate or amount of spawn added to the substrate also depends on the type of mushroom being grown. Some species are very particular about the type of substrate used, while others are flexible. Fussier species that are slow colonisers may need higher inoculation rates. The substrate's nutrient level is another factor that determines the inoculation rate. Low-nitrogen, carbon-rich materials like logs, woodchips, and straw can be inoculated outdoors in the open air, while most indoor methods require sterile conditions to avoid contaminating the substrate.
The cultivator's level of expertise also plays a role in determining the inoculation rate. For a new cultivator, a higher inoculation rate can boost the success rate. As the grower refines the cultivation process, they can gradually lower the inoculation rate and observe its impact on colonisation time.
Different inoculation methods, such as top spawning and through spawning, also influence the speed of colonisation. Top spawning involves placing the spawn on top of the substrate and letting it grow downwards, while through spawning involves mixing the spawn throughout the substrate.
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The culture stage
To begin, you'll need to gather supplies and equipment, including a mushroom culture or spawn. You can purchase or make your own mushroom culture. If you're creating your own, you'll typically need to use mushroom tissue or spores to grow mycelium in a nutrient-rich medium. This can be done in a petri dish or by creating a liquid culture.
The type of substrate you're using will dictate the level of sterility required during the culture stage. Substrates with low nutritional values, such as cardboard, straw, sugarcane bagasse, coco coir, and unsupplemented hardwood sawdust, don't require sterile conditions for inoculation. However, if you plan on creating grain spawn or using nutrient-rich substrates, you must inoculate the substrate in sterile conditions. For small amounts of substrate, a glove box or still air box can be used, while larger quantities are best inoculated in front of a laminar flow hood.
During the culture stage, it's important to maintain sterile techniques to prevent contamination. This includes working in a clean environment, sterilising equipment, and practising good hygiene, such as washing your hands before handling any materials.
Additionally, the culture stage involves deciding on the inoculation rate, which is the amount of mushroom spawn or liquid culture added to the substrate. The inoculation rate balances colonisation speed and the cost of spawn per pound or kilogram of mushroom yield. A higher inoculation rate leads to faster colonisation, but it doesn't necessarily result in a larger mushroom yield. As such, growers aim to use the minimum amount of spawn needed to colonise the substrate without significantly increasing colonisation time or the chances of contamination.
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Frequently asked questions
Mushroom inoculation is the process of bringing spawn (mushroom tissue or spores) into contact with a substrate (the medium the mushrooms will grow in) to initiate its growth and development.
The goal of inoculating is to introduce the mycelium culture to as many points in the substrate as possible, so that the mycelium can quickly colonise the substrate before competing organisms take hold.
Common substrates used for cultivating mushrooms include straw, sawdust, woodchips, freshly cut hardwood logs, compost, manure, cardboard, and paper.
Before inoculating a substrate, you will need to gather supplies such as mushroom culture or spawn, as well as equipment like a pressure cooker, a laminar flow hood, or a still air box.
The process for inoculating a mushroom substrate involves preparing the substrate by hydrating and sanitising it. Then, the spawn is introduced through drilling holes, cutting wedges, or mixing spawn into bags. Finally, the inoculated substrate is incubated by providing warmth and humidity for the mycelium to colonise.
