Michael Davis
Mushroom spawn is a living fungal culture, called mycelium, grown onto a substrate. It is the backbone of any mushroom-growing operation and is similar to a seed. Unlike seeds, mushroom spawn is grown from selected genetics and cloned for consistent production of a particular mushroom cultivar. Spawn is the carrier that holds a specific strain of mushroom mycelium in stasis until the cultivator transfers it into a substrate such as a wood log, straw, or compost. The goal of the spawn is to spread out bits of mycelium into its final habitat where it can grow, colonize, digest food, and ultimately fruit.
| Characteristics | Values |
|---|---|
| Definition | Living fungal culture, called mycelium, grown onto a substrate |
| Types | Plug spawn, Grain spawn, Sawdust spawn |
| Use | Plug spawn is hammered into freshly cut hardwood logs; Grain spawn is used for commercial indoor mushroom grows; Sawdust spawn consists of mycelium grown into hardwood sawdust |
| Production | Spawn is produced in a laboratory by incubating specialty mushroom strains and growing them into various forms |
| Function | Holds a specific strain of mushroom mycelium in stasis until the cultivator transfers it to a substrate; Provides the backbone to any mushroom-growing operation |
| Growth medium | Should be nutritious and allow for vigorous mushroom growth; Rye grain and wheat berries are commonly used |
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What You'll Learn
Mushroom spawn is a mycelium 'seed'
Mushroom spawn is a mycelium "seed" used for mushroom production. It is a living fungal culture, grown onto a substrate. The substrate is usually composed of small and homogeneous pieces to allow for vigorous mushroom growth. This enables the mycelium to spread aggressively after inoculation. The substrate should be nutritious and easily spreadable.
Mycelium is the white filamentous part of mushroom-forming fungi. It is a web-like network of small white threads often seen on the forest floor. Mycelium is the body of the fungi, while mushrooms are the reproductive structures. It can be easily cloned, and any cell can form a new and independent colony.
To make spawn, specialty mushroom strains are incubated in a laboratory, then grown into a variety of forms for use, including sawdust, grain, and plugs (hardwood dowels). Each of these, once colonized by mycelium, is referred to as spawn. Different types of spawn are made for use in different substrates. For example, grain spawn is used for commercial indoor mushroom grows, while plug spawn is used for outdoor cultivation.
To use mushroom spawn, cultivators inoculate their bulk growth substrate with it. After inoculating a substrate, the spawn's mycelium colonizes the substrate. Once the substrate has been fully colonized, the fungus produces mushroom fruiting bodies.
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Spawn is grown on substrates like grain, sawdust, and wooden dowels
Mushroom spawn is the living fungal culture, or mycelium, grown onto a substrate. It is the backbone of any mushroom-growing operation and is similar to a seed. However, unlike seeds, mushroom spawn is grown from selected genetics and cloned for consistent production. Spawn is grown on substrates like grain, sawdust, and wooden dowels.
Grain spawn is used for commercial indoor mushroom growth. It is not suitable for inoculating outdoor logs but is perfect for indoor cultivators or inoculating straw beds. Grain spawn is most often used to inoculate loose substrates like straw. The grain provides a nutrient boost to unsupplemented substrates. It is a perfect medium for spawn because it has a high nutrient content, is small in size, and is easily accessible. All of North Spore's grain spawn, for example, is produced using millet and wheat berries and is USDA-certified organic.
Sawdust spawn consists of mycelium grown into hardwood sawdust. It is flowable and can be poured into bags that hold sterilized logs and sawdust blocks. It is a preferred spawn for many commercial log growers because spawn delivery can be mechanized with specialized tools. It is also economical when purchased in large quantities. However, sawdust spawn is prone to drying, so substrates must be managed for moisture.
Plug spawn is the type of spawn sold in little bags at garden centers, co-ops, and farmers' markets. They are locally produced wooden dowels that have been grown with mushroom mycelium. To use plug spawn, you need access to freshly cut hardwood logs. Holes are drilled into the log, spawn plugs are hammered into the holes, and melted wax is brushed over the plugged holes to seal the log. This method is slower than using sawdust spawn, and colonization rates are slower. However, it is simple to use, requires no tools but a hand drill, and is great for small projects.
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It can be produced at home
Mushroom spawn can be produced at home, and doing so allows for greater control over the cultivation process and can be more cost-effective. Here is a general guide to producing mushroom spawn at home:
Preparation and Sterilization
Begin by gathering the necessary materials, including a sterile workspace, gloves, masks, and other protective equipment. Sterilize all equipment and tools using a pressure cooker or boiling water to eliminate any contaminants. Prepare the substrate, such as grain or sawdust, by sterilizing it in sealed bags or containers to prevent contamination.
Spores or Culture Acquisition
Obtain mushroom spores or a culture from a reputable source. Spore syringes or liquid cultures can be purchased online or from specialty stores. Alternatively, create your own spore print by collecting spores from mature mushroom caps and storing them in a sterile container.
Inoculation
In a sterile environment, inoculate the substrate with the spores or culture. For grain spawn, inject the spores into the grain using a spore syringe, ensuring even distribution. For sawdust spawn, mix the spores or culture into the sawdust substrate. Seal the containers or bags to maintain sterility and prevent contamination.
Incubation
Place the inoculated substrate in a warm, dark location with a consistent temperature between 65-75°F (18-24°C). The incubation period can range from two to four weeks, depending on the mushroom species and environmental conditions. During incubation, mycelium will grow and colonize the substrate, breaking down the nutrients and preparing for fruiting.
Maintenance and Expansion
Maintain sterility throughout the process by regularly checking for any signs of contamination, such as mold or discolouration. If expansion is desired, transfer mycelium from the original spawn to a new substrate, ensuring sterile conditions. Continue this process until the desired amount of mushroom spawn is achieved.
Fruiting and Harvesting
After the spawn has fully colonized the substrate, induce fruiting by exposing it to fresh air, light, and moisture. Create a fruiting environment by transferring the spawn to a specialized fruiting chamber or a humid, well-ventilated area with indirect light. Maintain optimal conditions for mushroom growth, including proper temperature, humidity, and airflow. Harvest the mushrooms when they reach maturity, typically when the caps are fully expanded and slightly curved inward.
Producing mushroom spawn at home requires patience, attention to detail, and a sterile working environment. By following these steps and adapting them to the specific mushroom species and available resources, hobbyists and cultivators can successfully create their own mushroom spawn for personal use or small-scale farming.
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Spawn is prone to contamination
Mushroom spawn is a complex, biological material and as such, it is susceptible to contamination by other microorganisms. Spawn contamination can occur at any stage of the mushroom cultivation process, from the initial spawn production to the final stages of mushroom fruiting. Contamination can render the spawn unusable and affect the yield and quality of the mushrooms.
The most common contaminants are bacteria and wild fungi. Bacteria can rapidly multiply and outcompete the mycelium for resources, while wild fungi can invade and overpower the spawn. Contamination can occur through airborne spores, unsterile equipment, or even contaminated water or compost. It is a constant risk that mushroom growers must manage.
Good sterile technique is essential to prevent contamination. This includes sterilizing equipment, using sterile materials, and working in a clean environment. Growers often work in sterile labs for spawn production, using laminar flow cabinets to ensure a sterile air environment. Sterile techniques are particularly important when transferring mycelium from one substrate to another, as this is a critical point of potential contamination.
Even with careful practices, contamination can still occur. It is important to regularly check spawn for signs of contamination, such as discolouration, odd textures, or unusual odours. If contamination is suspected, it is crucial to act quickly to isolate the affected spawn to prevent it from spreading. In some cases, contaminated spawn can be rescued by transferring healthy mycelium to a new substrate, but often, it must be discarded to prevent further issues.
Certain mushroom species are more prone to contamination than others. For example, the popular button mushroom, Agaricus bisporus, is relatively resistant to contamination, which is one of the reasons for its widespread commercial cultivation. Growers often select strains that demonstrate some resistance to common contaminants, especially in large-scale commercial operations.
Overall, spawn contamination is a constant risk in mushroom cultivation. While it can be challenging to manage, with good practices and quick responses to any issues, it is possible to minimize the impact of contamination and successfully grow mushrooms.
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Plug spawn is a popular type
To use plug spawn, one must have access to freshly cut hardwood logs. Holes are drilled into the logs, and the spawn plugs are hammered into them. Melted wax is then brushed over the plugged holes to seal the log. Plug spawn is slower than using sawdust spawn, and the colonisation rates are slower. However, it is still a great option for those who want to try growing mushrooms outdoors.
Plug spawn is a good option for small projects. It is also economical when purchased in quantity. However, it is prone to drying, so substrates must be managed for moisture. Proper waxing or other moisture barriers must be installed and monitored.
Plug spawn is a convenient way to get started with mushroom cultivation. It is simple to use and does not require any specialized tools or equipment. With plug spawn, one can easily grow mushrooms outdoors using freshly cut hardwood logs. This type of spawn is also locally produced and widely available at garden centres, co-ops, and farmers' markets.
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Frequently asked questions
Mushroom spawn is a living fungal culture, called mycelium, grown onto a substrate. It is used as a seed to grow mushrooms.
The three most common types of mushroom spawn are plug spawn, grain spawn, and sawdust spawn. Plug spawn is grown on wooden dowels, grain spawn is grown on grains such as rye or wheat berries, and sawdust spawn is grown on hardwood sawdust.
Mushroom spawn is used to inoculate a growth substrate, such as wood logs, straw, or compost. The spawn spreads out and colonizes the substrate, and then the fungus produces mushroom fruiting bodies.
