The Magic Of Commercial Mushroom Cultivation

Commercial mushroom farming is a lucrative business opportunity that can be started with minimal space and resources. The entire growing process begins in a laboratory, where spores are inoculated into sterile cereal grains, which then develop into spawn. This spawn is then sown into a substrate, typically consisting of straw or supplemented sawdust/wood chips. The substrate is placed in a controlled environment, such as a growing house or room, where temperature, humidity, and light levels are carefully monitored to induce fruiting and growth. Oyster and shiitake mushrooms are often the most profitable varieties due to their fast growth rates and ability to be grown indoors. Commercial mushroom farming can be started on a small scale and quickly become profitable, making it an attractive venture for entrepreneurs and farmers.

Growing mediums/substrates: straw, supplemented sawdust, compost, or wood chips

Commercial mushroom growers have a variety of growing mediums or substrates to choose from, including straw, supplemented sawdust, compost, or wood chips. Each type of mushroom prefers different substrates, so growers must choose the right one for their desired crop.

Straw is a common substrate for home and commercial growers, especially those just starting. It is an inexpensive option that can be purchased at farm shops, pet stores, and other locations that sell animal feed or bedding. Straw is also available in pre-treated and chopped bags, which can be used successfully for cultivation. However, straw does not produce the best yield and can be difficult to work with as it needs to be chopped for optimal results. Oyster mushrooms grow very well on straw and are the best species to grow on this substrate. The straw for oyster cultivation can be treated through fermentation, pasteurisation, or a lime soak.

Sawdust is another popular substrate choice for many types of mushrooms. Growers can use hardwood sawdust or supplement it with other materials like soy hulls or coco coir. Sawdust-based substrates are faster than logs, and supplemented sawdust formulas tend to colonise faster than other substrates.

Compost is another option for a growing medium, especially for common button mushrooms. This substrate is created through a two-phase composting and sterilisation process using manure and straw. Compost supplementation can also improve the nutritional status of mushrooms.

Wood chips, like sawdust, are derived from wood and are thus preferred by some mushroom varieties. The species of tree the wood chips come from matters, and many hardwoods are appropriate.

Spawn/inoculation: spores are inoculated into sterile grains, then sown

Spawn/Inoculation

The spores, or natural seeds of the mushroom, are so tiny that they cannot be handled by a person. Instead, they are carefully inoculated into sterile grains, which are then sown. This process should be done in a laboratory to ensure sterile conditions. The spores are injected into sterilized grains using a syringe. The syringe tip must be flame-sterilized before use, and the injection should take place in a still-air environment to minimize airborne contaminants.

The amount of spore solution injected depends on the potency of the syringe and the type of grain. A general rule is to use 1-2 ccs of solution for every pound of grain. However, some sources recommend 1-2 ccs per quart-sized grain jar, while others suggest using a smaller amount of spores for better results. It is important to note that using too much spore solution can cause bacteria to flourish and alter the H2O content in the jars.

The grains used for inoculation can be stored in the fridge for an extended period, depending on the species. For example, king, blue oyster, and shiitake grains can be stored for over four months and remain viable.

Once the grains are inoculated, they need to be placed in an undisturbed area with a temperature between 75 and 81°F (23.8-27.2°C). Signs of growth should appear within 3-10 days. After about three to four weeks, the mycelium will have colonized 70-75% of the bag. At this point, the grain is broken up to allow the mycelium to colonize the remaining area, which takes approximately another week.

Once the mycelium has fully colonized the compost, it needs to be transferred to fruiting conditions to induce the growth of mushrooms. This is done by changing factors such as temperature, oxygen levels, and humidity.

Fruiting/flushing: mushrooms fruit/flush in controlled conditions

Commercial mushroom cultivation is a complex process that requires careful control of environmental conditions. One of the most critical steps in this process is fruiting or flushing, which involves inducing the mushrooms to form fruiting bodies and produce mushrooms. This phase is influenced by species-specific growth patterns and environmental factors such as humidity, temperature, fresh air exchange, and light.

To initiate fruiting or flushing, growers manipulate the environment to signal the mycelium to form fruiting bodies. This can be done by making adjustments to humidity or temperature. For instance, dropping the temperature in the growing room below 20°C triggers the spawn to develop fruit bodies. Additionally, factors like optimal moisture levels, temperature, and air exchange rates play a crucial role in inducing flushes.

The substrate, which serves as the mushroom's "food," also influences the fruiting process. Substrates that are nutrient-rich can support more flushes and larger yields. Between flushes, the substrate may need rehydration to maintain moisture levels that are conducive to fruiting. This process of rehydration is known as "dunking."

Certain mushroom species, such as Oysters, Lions Mane, and Pink Oysters, are known for their ease of fruiting and ability to produce multiple flushes. However, other species like Shiitake require more specialised techniques, including longer colonisation times, physical stimulation ("smacking" the blocks), and cold shocking by placing them in a refrigerator.

By understanding and managing the flush cycle, cultivators can maximise their yields and ensure productive substrates throughout the mushrooms' lifecycle. This involves optimising conditions for each flush, timely harvesting at peak maturity, and managing contamination risks, as substrates become more susceptible over time.

Harvesting: mushrooms are hand-picked in stages over 2-3 weeks

Harvesting Mushrooms

Harvesting mushrooms is a delicate process that requires care and precision. The first mushrooms are ready for harvest in about three weeks. However, it's important to note that mushrooms mature at different times, so harvesting is done in stages over a period of two to three weeks.

The entire harvesting process is done by hand. Harvesters use trolleys equipped with built-in knives and weigh scales to collect the mushrooms. It is crucial not to touch the mushrooms until they are ready for harvest, as doing so could damage the crop.

The first flush of mushrooms is harvested over four to five days. After this initial harvest, the mushrooms are left to rest for about three days, during which they grow back. This process is repeated in stages or flushes, allowing for continuous harvesting over a two-to-three-week period.

The timing of the harvest is critical to the quality and size of the mushrooms. Mushrooms grow rapidly, doubling in size within 24 hours. Therefore, the harvesters must be vigilant in monitoring the crop to ensure optimal picking time.

To increase labour efficiency during harvesting, many growers opt for straw as a substrate. Straw is readily available and comes in compressed bales that are easy to store. By shredding the straw, growers can increase the surface area exposed to the mycelium, facilitating its movement and enhancing yield.

Drying and storing: post-harvest, mushrooms are dried and stored

Drying and Storing Mushrooms

Post-harvest, mushrooms are dried and stored. The process of drying and storing mushrooms varies depending on the grower and the species of mushroom. Here is an overview of some common methods and considerations:

Drying Techniques

• One common method of drying mushrooms is to use an electric or gas-powered shredder to shred the mushrooms before laying them out to dry. This technique helps to increase yield by breaking down the fibres and exposing more surface area, making it easier for the mushroom to grow.
• Another technique is to dry the mushrooms in a well-ventilated area, such as a barn or shed, by hanging them or laying them out on trays.
• For small-scale operations, a food dehydrator can be used to dry mushrooms.

Storage Considerations

• Mushrooms should be stored in a cool, dry place.
• To maintain freshness, dried mushrooms can be stored in airtight containers or bags.
• Proper labelling and dating of stored mushrooms are important for inventory management and product traceability.
• Some growers may choose to sell their mushrooms fresh to avoid the need for long-term storage.

Overall, the drying and storing process for commercial mushrooms is crucial to ensure product quality and longevity. By selecting appropriate techniques and storage conditions, growers can preserve their mushroom harvest effectively.

Frequently asked questions