The Reishi mushroom, scientifically known as Ganoderma lucidum or G. lingzhi, is a fungus with a long history of use in Asian traditions. Its reputation is built on its perceived health-promoting properties, which has driven widespread interest in its cultivation.
Preparing the Growth Medium
The cultivation process begins with preparing the substrate, which acts as the nutritional foundation for the Reishi mycelium. Since Reishi naturally grows on hardwood trees, the growth medium is typically composed of hardwood sawdust, such as oak, maple, or beech. This base material needs to be supplemented with a nitrogen source to provide the necessary fuel for vigorous mycelial growth.
Common supplements include wheat bran, rice bran, or soy hulls, generally mixed with the sawdust at a ratio providing 5\% to 15\% supplementation. The moisture content should be between 55\% and 65\%—a level where the substrate holds its shape when squeezed but only releases a few drops of water. Gypsum is often added to help balance the pH (5.5 to 6.5) and improve the substrate’s texture for better air exchange.
Once the substrate materials are mixed and hydrated, they must be sterilized to eliminate competing organisms like bacteria and mold. This is typically achieved by sealing the substrate in specialized polypropylene grow bags and heating them in a pressure cooker or autoclave. A common schedule involves sterilizing at 15 pounds per square inch (PSI) for 90 minutes to 2.5 hours, depending on the volume of the block. After sterilization, the substrate must be allowed to cool completely before the next step to prevent thermal shock and inhibit contamination.
Mycelial Colonization and Incubation
The next step is inoculation, where the sterile substrate is introduced to the Reishi spawn, which is the mushroom’s mycelium grown on grain. This transfer must be performed using sterile techniques, often within a clean workspace or a specialized flow hood, to maintain the purity of the substrate block. A small amount of the Reishi grain spawn is mixed into the cooled substrate bags, initiating the colonization process.
Following inoculation, the bags are moved to an incubation area where the mycelium can colonize the substrate completely. Reishi mycelium is a relatively slow grower compared to some other cultivated species, requiring a warm, dark environment, ideally between 75°F and 80°F. During this “spawn run,” the mycelium spreads throughout the block, transforming the loose substrate into a dense, solid, white mass.
Full colonization can take anywhere from three to twelve weeks, depending on the specific Reishi strain and the incubation temperature. A unique characteristic of Reishi is that the fully colonized mycelium may turn a yellowish-brown or reddish color, which is a normal sign of maturity and is not a sign of contamination. Once the block is completely firm and encased in the dense mycelial network, it is ready to be moved into fruiting conditions.
Triggering Antler and Conk Formation
Reishi’s final shape is dictated by the concentration of carbon dioxide (\(\text{CO}_2\)) in the air. This environmental control allows the cultivator to produce two distinct forms: the antler or the conk (shelf) shape. The transition from colonization to fruiting requires a drastic change in environmental conditions to initiate the mushroom’s development.
To produce the antler form, characterized by long, vertical, unbranched growths, the block must be kept in a high \(\text{CO}_2\) environment with minimal fresh air exchange (FAE). In this low-oxygen setting, the mushroom stretches upward in search of oxygen, creating the distinctive, pointed, deer-horn appearance. Humidity must be maintained between 90\% and 95\% to prevent the delicate growing tips from drying out.
Conversely, to encourage the formation of the shelf-like conk, the environment requires a significant increase in fresh air exchange. Lowering the \(\text{CO}_2\) concentration signals the Reishi to stop vertical growth and begin developing the characteristic fan-shaped, varnished cap. During this fruiting stage, temperature should be maintained between 70°F and 80°F, with humidity at 85\% to 90\%. Manipulating air exchange is the primary method used to control the final morphology of the Reishi fruiting body.
Harvesting and Drying Reishi
Timing the harvest depends on the desired end product, which is often dictated by the chosen growth form. Antler Reishi is typically harvested when the stalks reach the desired height, just before the white growing tip begins to flatten out, which can take several months. Conk Reishi is ready when the cap has fully expanded and the white growing margin on the edge of the cap has receded, often just before or as the mushroom begins to release its fine brown spores.
To harvest, the Reishi is simply cut at the base where it meets the substrate block using a sharp knife or shears. Because the mature fruiting body is tough and woody, it must be sliced into small pieces before drying to ensure proper preservation. Attempting to slice a fully dried Reishi is extremely difficult and can damage equipment.
The harvested pieces require thorough drying to preserve their compounds for long-term storage and use in teas or tinctures. A food dehydrator is the most effective tool, set to a low temperature, typically between 95°F and 115°F. The drying process is complete when the pieces are brittle and snap cleanly, ensuring the moisture content is low enough to prevent mold growth.