The mushroom Ganoderma lucidum, commonly known as Reishi, is prized for its unique growth forms, which manifest as either elongated, branched “antlers” or shelf-like “conks.” Cultivating this species indoors requires precise control over the environment and substrate preparation. This article provides a procedural guide for the successful indoor cultivation of Reishi, detailing the materials and techniques required.
Essential Supplies and Environmental Requirements
Successful indoor cultivation requires assembling the proper materials and establishing a controlled growing environment. The primary growth medium, or substrate, for Reishi is hardwood sawdust; oak, maple, or alder are effective choices. This bulk substrate must be inoculated with grain spawn, which is a cereal grain colonized by the Reishi mycelium. Components are mixed and placed into specialized, autoclavable polypropylene grow bags equipped with a micro-pore filter patch, allowing gas exchange while preventing contamination.
A pressure cooker or autoclave is necessary for sterilizing the prepared substrate. This process eliminates competing molds and bacteria, ensuring the Reishi mycelium has an uncontested food source. Beyond materials, surrounding conditions must be carefully managed to support each developmental phase. The incubation phase, where the mycelium colonizes the substrate, requires a consistently warm temperature, ideally 75 to 80 degrees Fahrenheit (24–27 degrees Celsius).
Once colonization is complete, the temperature can be lowered to 70 to 75 degrees Fahrenheit (21–24 degrees Celsius). Humidity is a sensitive parameter, needing to be maintained at 90 to 95 percent, especially during fruiting to prevent drying. Controlled fresh air exchange (FAE) is equally important, delivering oxygen while removing the carbon dioxide produced by the growing fungus. These factors must be monitored and adjusted to guide the organism through its lifecycle, dictating whether it forms the antler or conk structure.
Substrate Preparation and Inoculation Techniques
Substrate preparation directly impacts the success of the cultivation cycle, requiring careful measurement and sterile practices. Hardwood sawdust must be hydrated to 50 to 60 percent moisture content; when a handful is squeezed firmly, only a few drops of water should be released. Nutrient supplements, such as wheat bran or rice bran, may be mixed in to increase nitrogen and accelerate colonization. The addition of gypsum helps prevent substrate particles from clumping during sterilization.
After mixing the hydrated substrate and supplements, the mixture is loaded into the grow bags, leaving space for sealing. Sterilization is the next step: bags are placed inside a pressure cooker and heated to 15 pounds per square inch (psi) for 90 to 120 minutes. Maintaining this high pressure and temperature kills all competing microorganisms, creating a sterile environment. The bags must cool completely to room temperature before inoculation.
Inoculation involves introducing the grain spawn into the cooled, sterile substrate, demanding strict sterile technique to prevent contaminants. Growers utilize a still air box or a laminar flow hood to create a clean working area, minimizing airborne mold spores. The grain spawn is broken up and mixed thoroughly into the sawdust, ensuring the mycelial network is evenly distributed. Once inoculated, the bag is sealed, and the mycelium begins colonization, using the filter patch to manage gas exchange.
Managing the Grow: Incubation, Fruiting, and Harvesting
The incubation phase requires the inoculated substrate to be kept in darkness at 75 to 80 degrees Fahrenheit. This period, typically lasting two to four weeks, allows the white mycelium to spread rapidly, consuming nutrients and fully colonizing the block. Once the substrate block is covered in a dense, white network, the mycelial mass often thickens and turns yellowish-brown, indicating readiness for the fruiting stage.
Reishi cultivation offers the option of steering development toward either the “antler” or “conk” form, dictated primarily by the concentration of carbon dioxide (CO2). To encourage the elongated, branching antler structure, the substrate bag is left sealed, utilizing only the micro-pore filter patch for gas exchange. This high-CO2 environment simulates the organism’s search for fresh air, causing it to grow vertically in long, cylindrical points.
Conversely, to initiate the shelf-like conk, or cap, the grower must introduce a significant increase in fresh air exchange (FAE) to rapidly drop CO2 levels. This is achieved by cutting an opening in the grow bag and moving the block into a dedicated fruiting chamber where air is actively exchanged several times per hour. The sudden availability of oxygen signals the organism to stop vertical growth and begin horizontal expansion, forming the characteristic hard, shiny cap. Maintaining high humidity (90 percent or greater) is necessary to prevent the exposed surface from drying out.
Harvest timing depends on the desired final product and form. Antler Reishi is harvested when the stalks reach the preferred length or before the tips flatten and form a cap. Conks are ready once the white, soft growing edge, or rim, stops actively developing and hardens. The final product is harvested by cutting the mushroom cleanly at the base where it meets the substrate block.
Post-Harvest Processing and Storage
Following harvest, Reishi requires extensive processing due to its dense, woody texture and high moisture content. The mushrooms must be thoroughly dried to prevent spoilage and ensure long-term storage without developing mold or bacterial growth. To facilitate drying, especially for larger conk forms, the mushrooms are often sliced into thinner, uniform pieces.
The most effective method for removing moisture is using a food dehydrator set between 120 and 140 degrees Fahrenheit. Drying is complete when the pieces are brittle and snap cleanly when bent, ensuring all internal moisture has evaporated. Properly dried Reishi can be stored in an opaque, airtight container, such as a glass jar, in a cool, dark location away from direct sunlight and heat.
After the initial harvest, the remaining substrate block can often be rehydrated to trigger a subsequent fruiting cycle. This is achieved by soaking the spent block in cold water for several hours, which shocks the mycelium and replenishes moisture. After a resting period of a few weeks in the fruiting chamber, the block may produce a smaller second flush, maximizing the total yield from a single substrate preparation.