Mushroom spawn is the living foundation for growing mushrooms, acting as the fungal equivalent of plant seeds. It consists of mycelium, the vegetative growth of a fungus, cultivated on a nutrient-rich carrier material. The mycelial network produces the fruiting body, which is the mushroom that is harvested. Prepared spawn provides a reliable, fast-growing starting point for cultivation, bypassing the slow process of starting directly from microscopic spores. This active mycelium serves as the inoculum, introduced to a larger substrate to begin the colonization that leads to a successful harvest.
Where to Purchase Prepared Spawn
The most straightforward method for obtaining spawn is purchasing ready-to-use products from commercial suppliers. These specialized vendors, often mycological labs or dedicated online retailers, produce spawn under sterile, controlled conditions. Choosing vendors with a strong reputation for quality control ensures the product is contamination-free and the strain is viable.
Commercial operations use laboratory-grade cultures to ensure the spawn is aggressive and healthy. The purchased spawn is typically fully colonized, meaning the mycelium has completely permeated the carrier material, making it ready for immediate use. You will find a variety of options, including grain spawn, sawdust spawn, and plug spawn, available for popular species like Oyster, Shiitake, and Lion’s Mane.
Local agricultural suppliers or specialty nurseries may also carry mushroom spawn. Before making a purchase, confirm the spawn’s generation, as first-generation (G1) spawn generally offers the best vigor and yield potential. Checking the packaging date and confirming the expected shelf life ensures maximum viability.
The Process of Creating Your Own Spawn
Creating your own mushroom spawn involves propagating a mushroom culture onto a sterilized substrate, a process that requires strict sterile technique. This begins with a small, pure culture, often a liquid culture syringe, a tissue clone on agar media, or a spore syringe. The goal is to transfer this culture into a larger, nutrient-rich medium without introducing competing molds or bacteria.
The chosen substrate, commonly a grain like rye, millet, or wheat, must first be properly hydrated by soaking and then simmering briefly. This ensures the grains are moist but not waterlogged. The grain is then loaded into jars or heat-resistant bags with filter patches, which allow for gas exchange while blocking airborne contaminants.
Sterilization is performed using a pressure cooker or autoclave, which must reach 15 PSI for at least 90 minutes to eliminate all competing organisms. The sterile grain must cool completely before inoculation, which introduces the culture. The culture is injected through a self-healing port or introduced by transferring an agar wedge in a clean, still-air environment.
After inoculation, the containers are placed in a clean, dark area at an appropriate incubation temperature. Over several weeks, the mycelium spreads, appearing as a white, thread-like network colonizing the grain. Once colonization reaches between 30% and 50%, shaking the container helps redistribute the colonized grains, accelerating the final colonization process.
Understanding Different Spawn Substrates
The material used to carry the mycelium, the spawn substrate, is chosen based on the mushroom species and the intended cultivation method.
Grain spawn, made from sterilized cereal grains, is widely used for indoor cultivation due to its high nutrient content. Each colonized grain acts as an inoculation point, leading to fast and even colonization when mixed into a bulk substrate like straw or sawdust.
Sawdust spawn, typically made from hardwood sawdust, is a common choice for commercial mushroom blocks and inoculating logs. The fine particle size promotes rapid colonization of wood-based substrates. Sawdust spawn is effective for wood-loving species such as Shiitake, Lion’s Mane, and Reishi.
There are two other specialized types of spawn:
- Plug spawn consists of wooden dowels colonized with mycelium, designed for outdoor log cultivation. These plugs are hammered into holes drilled into fresh-cut logs, providing a simple method for growing wood-decomposing mushrooms outdoors.
- Liquid culture is a suspension of live mycelium in a nutritious water solution, primarily used for rapid expansion or for inoculating grain quickly via syringe.
Proper Handling and Storage
Once acquired or created, proper storage is necessary to maintain the spawn’s viability. Spawn is a living culture, and its shelf life is directly related to its storage environment. A cool, dark, and clean space is ideal for storage.
At room temperature, grain and sawdust spawn can remain viable for approximately four to eight weeks, though using it within two to three weeks of production is recommended for the best results. For longer-term preservation, commercial growers often refrigerate the spawn, which can extend its shelf life to three to six months by slowing the mycelial metabolism. Spawn should never be frozen, as this will damage the living cells.
Preventing contamination is a primary concern during handling; all tools and surfaces should be kept clean, and unnecessary handling should be avoided. Contamination is often visible as off-colors like green, pink, or black patches, or a sour, bacterial smell. If contamination is noticed, the spawn should be immediately isolated and disposed of to prevent spreading to other cultures or growing areas.