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• Grow Room Design
• Grow Room Maintenance
• Mushroom Growing
• Mushroom Grading
• Weekly Schedule (Example)
• Quick Reference Guide
• Appendix: Oyster Mushroom Information
• Appendix: Visual References

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Choose materials that are easy to clean, moisture-resistant, and provide insulation if possible. Common choices include moisture-resistant drywall, plastic tarps or sheeting, corrugated plastic panels, refrigerator panelling, and exterior house siding. Rigid materials are easier to clean than loose-flowing ones.

Opt for floors that are easy to clean and resistant to moisture. Examples include concrete, epoxy-coated flooring, or washable tiles. Avoid materials that may harbour contaminants or absorb water. Excess water accumulation on the floor can lead to an increase in bacterial growth requiring more frequent cleanings so having a sloped floor leading into a drain reduces the likelihood of any water buildup and allows for easy floor cleaning. Having a drain regardless of a sloped floor is highly recommended but not a requirement. If a drain does not exist in your intended space, creating a raised floor is an option, but must be sealed well to ensure water does not leak out into the surrounding area.

Insulating the grow room helps maintain a more stable temperature and partially protects against external weather conditions. A variety of insulation options are available from rigid foam boards to rolled wool batts. Although not a requirement, your choice of material will be primarily price-motivated and dependent on your grow room’s location & the seasons in which it will be operating.

Mushrooms require indirect or diffused light for optimal growth & colour formation. LED lights are energy-efficient, and often cheaper when looking for specific color & lumen values. Each of my lights are 2200 lumens with a color temperature of 6500k, and I use 3 for a 60 sq.ft space. I would recommend a lumen value anywhere from 1400 to 2200 and a color temperature of 4500k to 6500k. Position the lights above the growing shelves, spaced out to ensure even light distribution amongst the whole space. Generally, a 12-16 hour light cycle per day is suitable for promoting fruiting. Timers or automated lighting systems can help maintain consistent light schedules.

Fresh air exchange (FAE) is one of the most important factors when considering the design of a grow room. All mushrooms inhale oxygen and exhale carbon dioxide. High levels of CO2 can lead to reduced oxygen availability, hindering mushroom growth and leading to elongated, weak stems, smaller caps, and especially poor yields.

Install at least 1 air vent or duct to allow the intake of fresh oxygenated air. Though filters may slow the flow of air coming into the grow room, the use of filters is recommended to prevent the entry of contaminants from the outside environment. The use of an in-line fan to push the air into the room is not necessary as the exhaust fan will pull air into the room through your intake vent. Intaking air from an internal building that is climate-controlled will affect your room’s temperature & humidity differently than intaking directly from the outside.

Install fans to promote air circulation within the grow room. A simple 6” fan running on low during the same interval as your humidity controller may be enough for proper circulation of humidity and fresh air. I’ve found a 20” box fan mounted to the ceiling in the center of the room circulates air well by bouncing the air off the floor. Regardless of the size or direction of the circulation fans, the goal is to remove pockets of stale air and to properly spread the humid air among the growing mushrooms. Areas farthest away from your intake & exhaust vents will generally have the least natural circulation. Attachment methods that are easy to remove are recommended for regular cleaning of the fan.

It is important to set up an exhaust system to remove excess heat, carbon dioxide, and spores from the grow room. Most grow rooms run using a negative pressure system, i.e. most of the airflow is created from the exhaust fan pulling air out of the room. It is ideal to place the exhaust at the opposite side of the room as your intake so the air flows through the room. Failure to exhaust the spent stale air will result in too much build-up of carbon dioxide and spores spreading to your work environment outside of the grow room which not only poses a cleanliness issue but also has risks regarding health and safety.

Exhaust fans will slowly become clogged with mushroom spores so connecting exhaust fans to ducts or vents located in easy-to-reach areas either inside or outside the grow room allows you to swap out and clean exhaust fans regularly (i.e. weekly). I recommend buying two of the same exhaust fans and swapping them out each week to allow the most recently cleaned one to sit & dry fully over the week.

Every fan has a CFM value used to determine the amount of air that will be recycled while the fan is running; using this value to properly size your fan for the dimensions of the grow room is very important: your fan’s CFM should be able to recycle the full volume of air in your grow room in around 3 minutes. I’ve found it to be beneficial to have the exhaust fan cycle off for 10% of the time to allow the humidity to build up if the humidifier is running constantly.

The formula for CFM calculation:
(area of room in sq.ft. * height of room in ft. * number of times per hour the air must be exchanged) / 60 min = X ft3/min or X CFM. i.e (64 sq.ft x 8ft x 20 times per hour)/60 mins= 171 CFM

Mushrooms thrive in a specific range of humidity levels. Maintaining the appropriate humidity is vital for successful fruiting, perhaps even more important than FAE.

Installing at least 1 humidifier to control and maintain optimal humidity levels for the grow room is a requirement. Humidifiers add moisture to the air when needed and can act as additional filtration for incoming air when combined with a submersible UV sterilizing light. DIY-built humidity bins using ultrasonic pond misters inside an airtight plastic bin with a waterline in-feed & float valve are commonplace in the industry and are often encouraged because of their versatility and ease of repair or replacement (link found in the link section). Humidifiers can be placed outside the grow room which then vents into the grow room through a duct, or they can be placed directly inside the grow room, but will often fill with sludge from the intake of spores if they are not receiving fresh air from outside the grow room.

Using a hygrometer or humidity sensor to monitor your grow room is a requirement. This allows you to adjust the humidifier settings accordingly and ensures that the humidity levels remain between 80-90%. Too low humidity means the mushrooms dry out & grow less; too high humidity means the mushrooms get soggier and contamination rates increase.

Some growers utilize automated misting systems to provide periodic misting of fine droplets of water, helping to maintain humidity levels and promote mushroom growth but this is not something I have any experience with.

All mushrooms prefer to grow within a specific temperature range.

• The broad temperature range for their general growth and fruiting typically falls between 15-25°C. Blue oysters in particular prefer lower temperatures closer to 16-18°C.
• Lower temperatures in the range promote less bacterial growth & contamination rates than higher temperatures in the range.
• Too low of temperatures (dipping below 10°C) mean the mushrooms grow much slower or not at all.
• Too high temperatures (approaching 30°C) mean the mushrooms may exhibit signs of heat stress & have shorter prime harvesting windows.
• The existing temperature of the air you are intaking to the grow room will directly affect the grow room’s temperature. Growing in hot summers & cold winters both have unique considerations for temperature control to achieve the milder temperatures needed for ideal mushroom growth.

To ensure optimal growing conditions for your oyster mushrooms, it can be beneficial to create a separate space for preconditioning the grow room air outside of the grow room. This space, sometimes referred to as the plenum, allows you to adjust and control factors such as temperature and/or humidity in a controlled space before it enters the grow room.

The plenum is typically situated between the fresh air intake and the grow room. It can be a separate room or a smaller contained area within the ventilation system.

The plenum serves as a buffer zone that allows you to heat, cool, or humidify the incoming air before it reaches the grow room. Instead of blasting hot or cold air directly into your grow room, disrupting the consistent atmosphere you’re aiming for, you would instead control the air temperature and relative humidity within the plenum and then vent it into the grow room.

The plenum can also house your air filtration systems, such as HEPA filters or carbon filters, to remove impurities, dust, or potential contaminants from the incoming air.

Optimizing the available space in the room will lead to an increased number of grow blocks in the grow room and reduced costs associated with humidifying, heating/cooling, and cleaning. Having your grow room door open outwards rather than inwards or keeping your humidification system outside the grow room are some optimizations to the amount of space available for grow blocks, but by far the most important aspect of your room will be your choice of shelving and its organization.

Shelving options available for fruiting mushrooms come in a variety of different styles, sizes, and materials.

Stationary shelves are often fixed in place and provide a stable platform for your growing needs. Stationary shelves are a popular choice for their low cost and ability to be custom fit into any configuration/size. Their downside is most evident when it comes time to clean them as removing them (or the active blocks on them) from the grow room can be quite cumbersome, if not impossible, and they may be in the way when trying to scrub the floor or walls situated around them.

Rolling shelves offer the advantage of easy mobility. These shelves are equipped with castors or wheels, allowing mobility around the grow room or removal from the grow room as needed. This is beneficial when you want to reconfigure the layout, clean the grow room, or access different areas for maintenance or harvesting. Rolling shelves come with the highest cost and maintenance as the wheels may rust or get clogged needing attention or full replacement.

Wall-mounted shelves are attached to the walls of the grow room, maximizing floor space and providing a clean and organized setup. They are ideal for small grow rooms or spaces where you want to optimize vertical space utilization. However, it's important to ensure that the walls can support the weight of the shelving and the equipment placed on them.

Opt for materials like treated wood, stainless steel, plastic-coated/chrome wire, or other non-corrosive and moisture-resistant options.

Select shelving units that are sturdy and can withstand the weight of several to dozens of grow blocks, which weigh approximately 10 lbs each.

Opt for shelving that can be easily cleaned and sanitized on all sides & crevices to help maintain a hygienic growing environment.

Choose shelving options that allow for moderate airflow between the shelves to promote proper ventilation and prevent the buildup of stale air.

The height of each shelving section should take into account the height of the bags, and the method for fruiting (i.e. top fruiting or side fruiting). If side-fruited, no extra space is needed above the bag; if top-fruiting, allow for an extra 10-12” of space above the bag height for mushrooms to grow. The width & depth of the shelf should take into consideration how many blocks can fit on it to optimize for as little wasted space as possible. Blocks can be laid on their long flat face or their shorter side face, but are less stable to stand upright on their short side, so shelving that supports them at the back is recommended for this orientation.

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It's essential to maintain a clean and sanitized environment throughout the growing process. This helps prevent the introduction and growth of contaminants such as mold or bacteria.

Thoroughly clean all equipment, surfaces, and containers that will come into contact with the blocks and mushrooms. Use mild detergent or sanitizing agents to remove any dirt, debris, or residual organic matter. Rinse well to ensure no traces of cleaning agents are left.

Apply a disinfectant solution to cleaned surfaces and equipment to further eliminate any remaining contaminants. Common disinfectants used in mushroom cultivation include hydrogen peroxide, bleach, and/or 70% rubbing alcohol.

Maintain proper hand hygiene by washing hands thoroughly with soap and water before handling any materials, working with the mushrooms, or using disposable gloves.

Ensure a clean and dust-free environment by regularly cleaning the grow room and its surrounding area. Maintain a relatively clean air filtration system and minimize the entry of contaminants by keeping the grow room door closed.

Be sure to use clean and disinfected tools, gloves, and equipment to avoid cross-contamination between newer and older grow blocks as older blocks nearing the end of their lifespan are more likely to have higher levels of contamination.

Regularly inspect your mushroom crop for any signs of pests or diseases. Look for visible pests, unusual growth patterns, discoloration, spots, or mold formation. Isolate and remove any contaminated/infected blocks or mushrooms immediately to prevent the spread to healthy blocks.

A weekly deep clean of the grow room is required to keep contaminants at bay. The timing of the cleaning should be based around the current exposure of mushroom fruiting bodies, ideally, cleaning directly after a big harvest is most effective to reduce time wasted in moving active blocks out of the way.

Start by shutting down and removing all equipment, shelving, and materials that can be removed from inside the grow room at this time. This includes any empty shelves, spent blocks, or debris. Cleaning around currently growing blocks is possible but requires careful attention to detail to avoid harsh cleaners coming in contact with mushroom fruiting bodies; moving them to a temporary shelf outside the grow room is possible for short periods of time.

Begin the cleaning process by removing any visible dust, cobwebs, or debris from the walls, ceiling, and corners of the grow room. Pay special attention to hard-to-reach areas and areas out of direct line of sight.

Prepare a mild bleach cleaning solution then using a sponge, brush, or cloth, clean the walls, ceiling, and all visible surfaces within the grow room.

Use a heavy disinfectant to mop or scrub the floor. Rinse well and squeegee any standing water into available drains. Afterwards, ensure the drain is clean and free from any build-up or growth of foreign bodies.

Clean and sanitize all equipment, containers, shelves, and tools that will be used in the grow room. Scrub or soak them in a sanitizing solution, rinse thoroughly, and allow them to dry completely before returning them to the grow room.

Check and clean any air filters used in the intake system and remove the main exhaust fan(s) and circulation fan(s) to allow a thorough washing outside of the grow room (high-pressure water should suffice for washing these without needing a cleaning agent). Replace the circulation fan, and the exhaust fan with the fan cleaned in the previous week to allow a full week of drying.

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Adding new blocks to the grow room is known as fruiting the blocks and primarily comprises cutting into the plastic of the mushroom grow block and exposing it to the grow room environment.

There are dozens of different cuts you can make and a few different orientations the blocks will grow in the grow room. My preferred method is to use a clean box cutter or scalpel and make an "X" shaped incision on the largest side surface of the bag. The incision should be about 3 inches long and should penetrate through the plastic exposing the myceliated substrate beneath, without cutting into the mycelium itself too deeply. The exposed area allows for increased oxygen exchange, which promotes the formation of mushroom pins and subsequent fruiting.

Once the "X" incision is made and the mycelium is exposed, carefully place the mushroom block into the fruiting environment. I generally place the folded side of the bag on the underside to discourage mushrooms from growing into the headroom at the top of the bag. Ensure that the block is positioned securely and that it has sufficient space in front of the cut area for the fruiting mushrooms to develop.

Proper harvesting and post-harvest handling are essential for maximizing the quality, freshness, and shelf life of oyster mushrooms. A very sharp & fine blade such as a fish fillet knife I’ve found is ideal for cutting through the awkwardly shaped & spongy stems.

Oyster mushrooms are typically ready for harvest 8-10 days after exposing the block to fruiting conditions. The prime time to harvest is when the edges of the caps start turning upwards & expose more gills when it’s changing from curled in to flattened out. They should be plump & firm and have a strong, uniform color. Harvesting too early may result in smaller-sized mushrooms, while waiting too long may cause the caps to flatten out completely creating delicate/limp edges that crack easily when handled, a paler colour, and a soggier texture.

To harvest oyster mushrooms, hold the ‘head’ of mushrooms with two hands and gently twist & pull away from the block, or support the head with one hand & cut the mushrooms at the base of the stem, close to the substrate or growing block. Avoid excessive handling or rough harvesting techniques that could damage the mushrooms. Cut away any remaining mushroom debris or substrate from the harvested mushrooms before storing.

Handle the harvested mushrooms with care to avoid bruising, crushing or tearing, as this can affect their quality and shelf life. Minimize exposure to direct sunlight or excessive heat during handling & storing, as it can cause the mushrooms to wilt, dry or deteriorate quickly.

Oyster mushrooms are best stored in a cool and humid environment immediately after harvest. The ideal temperature for storing oyster mushrooms is around 2-4°C, i.e. typical fridge temperatures. Place the mushrooms in breathable packaging, such as paper bags or perforated plastic bins, to allow for air circulation and prevent excessive moisture buildup. Avoid storing oyster mushrooms in airtight containers, as it can promote condensation and lead to waterlogged or otherwise limp mushrooms.

Freshly harvested oyster mushrooms can be stored in proper storage conditions for 7-10 days, up to two weeks at the extreme end for heartier species of oyster. However, I recommended selling/delivering the mushrooms to customers within the first 72 hours after harvest to ensure the best quality & to give them ample time to use the mushrooms within the following week.

After harvesting the first flush of mushrooms from the block, you can choose to continue growing subsequent harvests, or “flushes”. Doing second flushes increases complexity in the scheduling of your grow room block cycling, but increases the value derived from each block.

Carefully inspect the surface of the substrate and remove any remaining mushroom fruiting bodies/growth from the surface of the substrate leaving a relatively smooth & clean surface for new fruiting bodies to form during the second flush.

Some growers choose to lightly mist the surface of the substrate with water after removing the first flush. This helps maintain the moisture levels necessary for the initiation of the second flush. However, be cautious not to oversaturate the substrate, as excessive moisture can increase the risk of contamination.

It is important to note that second flushes of oyster mushrooms usually have a lower yield compared to the first flush and take longer to develop. Be patient and continue to monitor the progress of the substrate. The timing of the second flush can vary, but it typically takes around two weeks and yields half the amount of a first flush.

• Once a block has finished its second flush it has used most of the nutrients available in the block for fruiting body production, it is considered spent and more attempts at growing will result in diminishing returns for yields and higher risk of contamination the longer the block exists in a humid environment.

• A spent block is suitable to use in composting as it still has a lot of nutrients to offer. The plastic bag must be cut off and put into the garbage.

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All cultivated mushrooms must lie somewhere in this grading system for them to be considered for sale or distribution.

Cultivated mushrooms in this class must be of superior quality. They must be free from defects & deterioration, with the exception of very slight superficial defects, provided these do not affect the general appearance of the mushroom, the quality, and the presentation in the package.

• They must be free of any substrate material.
• They have a non-jagged edge with no tears in the cap.
• They have an even, deep color.
• They have been picked within the optimal time frame.

Cultivated mushrooms in this class must be of good quality. The following slight defects may be allowed, provided these do not affect the general appearance of the produce, the quality, and the presentation in the package:

• Slight defects in shape and size.
• Slight defects in the coloring.
• Insignificant superficial bruising.
• Traces of substrate material.
• Harvest window marginally early or late.
• Minor tears in the cap.

This class includes cultivated mushrooms that do not qualify for inclusion in the higher classes but satisfy the minimum requirements. The following defects may be allowed, provided the mushrooms retain their essential characteristics of quality and presentation:

• Defects in shape.
• Defects in coloring.
• Slight bruising.
• A considerable amount of substrate material is present.
• Discoloured edges or feathering of the edges.
• Major tears and perforations in the cap.

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• Pick & store any harvest-ready mushrooms grown over the weekend
• Remove 2nd flush spent blocks for composting & clean empty shelves
• Fruit new bags

• Pick & store (or pre-pack) any harvest-ready mushrooms

• Pick remaining harvest-ready mushrooms
• Pack for Wednesday deliveries
• Minor mid-week cleaning of operation.
• Make deliveries

• Pick & store any harvest-ready mushrooms
• Deep clean harvesting area & cold storage

• Pick remaining harvest-ready mushrooms
• Pre-pack Saturday deliveries & Market crop
• Remove 2nd flush spent blocks for composting & clean empty shelves
• Deep clean grow room

• Make deliveries & do farmer’s market

• Rest day

• Walk the grow room looking for problem areas, contaminated blocks, or faulty equipment.
• Clean debris from the grow room floor and shelving.
• Wash & sterilize any used surfaces, tools, containers, etc. 3.

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The 5 pillars of grow room balance: Fresh air, humidity, temperature, lighting, and cleanliness.

• Relative humidity of 85%.

• Temperature of 16-20°C.

• Lights on for 16 hours each day.

• Carbon dioxide (CO2) concentration of around 1,000-1,500 parts per million (ppm).

• Precondition the air to be cooler if hot summer temperatures exceed 20°C

• Oyster production aligns well with a recurring weekly schedule to align with the growth time of 8-10 days

• Fresh mushrooms should get out to customers no more than 72 hours after harvest

• Oyster mushrooms can produce anywhere from 2 to 4 flushes with a total yield of 3-4 lbs per 10 lbs growing block. The average first flush is 2 lbs, average second flush is 1 lbs.

• It’s recommended to wear a half-face cartridge respirator mask when inside the grow room for periods longer than just a few minutes. This is to avoid excessive intake of spores into the lungs and sinuses as this can lead to fungal infections or anaphylactic shock.

• If oysters are looking leggy in their stem, likely not enough fresh air exchange.
• If oysters are growing slowly, the temperature or humidity might be too low.
• If oysters are showing dark discolouration, it may be from excess water falling on the caps; if pale & orange discolouration, it may be from contamination or heat stress.
• If small frilly nubs are forming on the top of caps, this is normal, it’s just extra growth attempting to start on the surface of caps.

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Oyster mushrooms (Pleurotus spp.) are a type of edible fungi that belong to the Pleurotaceae family. They are named "oyster mushrooms'' due to their characteristic shape, which resembles an open oyster shell. They are found growing on decaying or dying hardwood trees in the wild and have gills on their underside. Oyster mushrooms have a unique appearance, with a variety of possible colours depending on which species it is, broad, fan-shaped caps of varying sizes, and a smooth texture with varying thickness, from thick & plump to thin & delicate.

Oyster mushrooms are one of the easiest mushrooms to grow at a commercial scale.

Oyster mushrooms have a short growth cycle compared to many other mushrooms. Under optimal conditions, they can be harvested 8-10 days after introducing the mycelium to fruiting conditions. This fast turnaround time allows for weekly harvesting cycles throughout the year.

Oyster mushrooms are known for their prolific fruiting. They can produce large clusters of mushrooms, known as flushes, during each growing cycle. Oyster mushrooms can produce anywhere from 2 to 4 flushes with a total yield of 3-4 lbs per 10 lbs growing block.

Different species of oyster mushrooms can tolerate a wide range of temperatures, typically between 15-25°C, with varieties like blue oysters preferring lower temps, and varieties like pink oysters preferring higher temps.

One significant advantage of cultivating oyster mushrooms that prefer lower temperatures (Blue oysters prefer 16-18°C) is the reduced risk of contamination. Contaminants, such as molds and bacteria, tend to proliferate more rapidly at higher temperatures. By keeping the temperature on the lower side of the optimal range, you create an environment less favorable for contaminants.

Oyster mushrooms grown at lower temperatures often exhibit desirable characteristics such as thicker stems, larger caps, and better texture. These factors contribute to an improvement in visual appeal and culinary qualities.

While oyster mushrooms require some light for proper fruiting, they do not grow well under direct sunlight. Diffused or indirect light is sufficient, allowing growers to use artificial lighting sources to provide the necessary illumination.

The tools and equipment required for oyster mushroom cultivation are relatively simple and inexpensive compared to many other crops. Basic supplies include containers, shelving, humidifiers, circulation & exhaust fans, lighting fixtures, and thermometers & hygrometers.

Oyster mushrooms are good for either side-fruiting or top fruiting, which allows for flexibility in choosing shelving arrangements that work best for your room and are not constrained to only one type of fruiting.

Oyster mushrooms have a mild, delicate flavor with subtle hints of woodiness and a tender, meaty consistency, making them versatile ingredients in various dishes.

Oyster mushrooms can be prepared and cooked in numerous ways, including sautéing, stir-frying, grilling, roasting, or even used raw. They absorb flavors well, making them suitable for a wide range of cuisines and recipes, such as stir-fries, omelettes, soups, salads, pasta dishes, sauces, and more

Oyster mushrooms are low in calories, fat-free, and cholesterol-free. They are a good source of dietary fiber, vitamins (such as B vitamins and vitamin D), minerals (such as potassium and iron), and antioxidants.

Oyster mushrooms are a popular choice among vegans and vegetarians as they provide a meaty texture and umami flavor, making them a satisfying substitute for meat in many recipes.

Oyster mushrooms contain bioactive compounds like polysaccharides, phenols, and flavonoids with antioxidant properties, protecting against oxidative stress and chronic diseases.

Oyster mushrooms contain beta-glucans, which boost the immune system by stimulating immune cell activity, enhancing defence mechanisms, and potentially combating infections.

Oyster mushrooms may help modulate the inflammatory response, reducing the production of pro-inflammatory molecules and promoting the release of anti-inflammatory substances, contributing to a balanced immune response and potentially mitigating chronic inflammation.

Oyster mushrooms have also been investigated for their potential anti-cancer properties, cholesterol-lowering effects, and anti-diabetic properties. However, further research is needed to fully understand and validate these potential benefits.

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