Plenty of mushrooms can be grown in a relatively small space. The essentials for mushrooms to survive are:

  • Fresh Air
  • 12 Hours light cycle
  • Relative humidity from 80% upwards
  • The correct temperature

To accomplish this you will at least need a 6 X 3 meter grow house. a Well insulated Wendy House can work perfectly. Cover the inside with a layer of plastic, then a layer of 50mm isotherm and clad that with Newtech board. Paint the inside of your grow house with an anti-fungal paint. It is also advisable to have a drain and concrete slab in your grow house to be able to maintain a clean environment.

When looking at the fresh air requirements for your grow space, most mushrooms need the air to be exchanged 4 times an hour. Work out the cubic meter space of your grow room (L X W X H) and purchase an inline fan powerfull enough to do four air exchanges per hour. Rather push air into the grow space, as this will maintain a positive pressure. Have a filtered exhaust exit on the opposite side of the grow room.

For humidification I prefer using the ultrasonic humidifiers available from Green Thumb Hydro.

For lighting use LED strip lights, these will cost you less in the long term. Have them on a 12 hour timer switch. 

For winter temperature control, have one or two wall mounted eco-heaters on a thermostatic switch to control the exact temperature.

It is advisable to have a separate room for incubation, this room is dark, but also needs fresh air as well as a steady incubation temperature.

I recently had quite a large order to fill, growing oyster mushrooms. The time I was given to complete the project was slim and I decided to use straw as a substrate instead of wood shavings. I found myself in a pickle, since I have not used hot water pasteurization for a while and the steaming vessel I use was too large for the amount of straw needed. It was time for a new plan.

I set off to Game and purchased 6 X 56L Black tubs with lids. I was going to try my hand at using Calcium Hydroxide as a sterilizing agent to prepare the straw for my Oyster mushrooms. Here is the procedure I followed:

As with all other mushroom related work, remember to keep everything clean, wash all equipment with a bleach solution before use. Make sure your clothes are clean and the room used for inoculation is clean and the air was scrubbed with a bleach solution (10% bleach + water = 100ml + 900ml water).

The straw bales were chipped into pieces using my electrical wood chipper.

Add 150g of Calcium Hydroxide to each 56L tub + 50g of Gypsum.

Fill up the tubs 3/4 way with clean rain water - this produced a milky white liquid. (MIX WELL)

Next I stuffed as much straw into each tub as would comfortably fit, and filled with water to the brim. Once I closed the lid, all the substrate was submerged in the milky water.

Leave the tubs standing like that for 16 hours. (Any time between 14 and 18 hours.)

After this time, the tubs were turned on their sides to drain the water. I left them like this for 2 - 3 hours.


Next was time to shower and put on some freshly ironed clothes, just to make sure that I am not the source of any contamination ;) Wear some latex gloves when working with the straw and wash them down with a water/bleach solution from time to time or use an alcohol solution to wash your hands in between completing each bag. I washed down the surfaces I would be working on and sterilized the air twice with a 10% bleach/water solution using a misting bottle (avoid breathing in the mist!).

Use fresh good quality spawn only.


The substrate was bagged and inoculated using the sandwich spawn method (layering straw and spawn seeds).

layer-spawn add-spawn 

The completed bags were punctured with my pocupine quil (rince the puncturing tool with a bleach solution in between use for each bag to avoid cross contamination). Each bag received 30 - 40 holes on average. The bagged substrate was placed in my incubation room at a steady temperature of 21°C. 


After 6 days incubation, the smaller bags I made for testing purposes was completely white with mycelium and no sign of contamination.


The mycelium seems to run with extra vigour through this substrate. (This may be a result of the added calcium)

The above pictures was taken 9 days after inoculation. (The bag is weighing in at 4 Kilogram)
And the following pictures was taken 5 days after placing the bags in my grow room.
pinning ostreatus
pinning ostreatus
pinning ostreatus
And this was taken 10 Days after moving into my grow room.
flushing ostreatus
flushing ostreatus
flushing ostreatus
Tomorrow on day 11 I will start harvesting the first oyster mushrooms from these bags. (Total - 20 DAYS to harvesting my first flush :)

In conclusion I really like the Calcium Hydroxide method of sterilizing. I will post more regarding this project as we go along.

The second set of pins is happening now - 6 weeks after inoculations. I dropped the room temperature to below 14°C for 48 hours to help initiate pinning of mushrooms.

Some huge oyster mushrooms ready for harvest on my second flush. We have harvested 14kg of usable mushrooms this far and more to come.

How to easily build a simple DIY steaming vessel for mushroom substrate sterilization:

The first thing to do is find a suitable containing vessel for your mushroom steamer. I used a 5000L tank, that was used previously for storing fuel. This vessel was cut in half and cleaned out. At our local blacksmith, I had a basket manufactured that could hold about 120 bags of mushroom substrate (see pictures below). This basket fits inside the steaming vessel with enough space around the edges for steam ventilation.

mushroom steamer
steamer top
steamer covered

Use a high pressure gas burner and propane gas for heating the water (other ways can be used to heat the water, including wood fire and electricity.) It will take about 12kg of gas to successfully sterilize 120 substrate bags for 5 - 6 hours. Use enough water under the basket to last the 6 hours of steaming. If the water runs out, the dry heat will damage your substrate bags.

Cover the steamer to maintain constant temperature and steam flow. Some steam will naturally escape. I use three blankets and a tarpaulan to cover my steamer and then tie the covering tightly around the edge of the steamer.

Please also read: Cold Water - Sterilize with Calcium Hydroxide

There is a lot to say about cultivating a crop of your own mushrooms. "Firstly it's NOT like growing beans, but surely much more rewarding." The first time I saw the pinning mushrooms developing into fruit, is one of my fondest memories. For those out there that might want to take this up as a hobby, I have compiled some guidelines.

The Oyster mushroom family, Shiitake, Reishi and the Lions mane mushrooms are all part of a group of fungi called Saprophytes. In Nature Saprophytes will break down dead wood into humus and minerals. Typically mushrooms favor the type of wood / tree that they will inhabit. Shiitake loves the Oak tree stumps and Oyster mushrooms prefer poplar tree wood, being much softer than for instance Iron Wood or Black Wood trees. Generally speaking, avoid all aromatic woods, the rule of thumb is to use broad leaved trees that retains their bark well.

1: Choose the Type of mushroom and the substrate (food source for the mushroom) favoured by the mushroom.

  • It is important to find a substrate (the medium we use as food for the mushrooms) that is easily available to you. Having to travel far to collect your substrate will increase production cost.
  • Wheat straw is one of the better substrates to use for Oyster mushroom cultivation. Use clean, uncontaminated chopped straw only. Do not chip too fine, 4-10cm pieces is perfect.
  • Poplar leaves, banana fronds, coffee grounds, cotton seed meal can be added sparingly. Many other farm waste/recyclable materials can be used to supplement your substrate.

2: Choose the Production Method

  • For those that use wheat straw as the main substrate, the pasteurization process can be used to prepare the substrate for the mushroom. Pasteurization does not sterilize the substrate but will remove the unwanted contaminants and retain the beneficial bacteria. This process is the easier and faster of the two but will consume more water.
  • For those using wood chips and shavings as the main substrate, I recommend either autoclaving the prepared substrate bags or by steaming the prepared substrate bags for 5 - 6 hours. Prepare the wood chip / shaving and supplement mix to a moisture level of 55%, tightly pack the substrate into your bags and fold over the top 10cm of the bags. Use a rubber band to keep the bag closed.

A |  Pasteurization - STRAW - The tools needed for this process is a 210 liter steel drum (a large oil drum), a meshed basket to hold the substrate, a high pressure gas regulator and burner as well as access to water. Preheat the water in the steel drum to 65°C. Next lower your meshed basket with straw into the warm water. Place a weight on top of the straw to avoid it from floating up. Keep the temperature steady and leave the straw to soak in the water for 1 and a half hours. Now remove the meshed basket from the water or drain the water from the drum. The meshed basket with straw will be heavy; you may need an extra hand to pick it out of the drum. The straw needs to rest for some hours until it cools enough to receive the mushroom culture.

B | Steam sterilization - WOOD - Premix and bag your substrate. Prepare your steaming container. You can fit quite a couple of small substrate bags into a 210 liter steel drum. Pack the bags into your wire meshed basket. Allow some space under the basket for the water you will use to steam the bags. The boiling water underneath must not touch the bags. Fill the drum with water - the bottom 10 - 15 cm. You will come to know the exact amount of water to use after you have done the procedure a couple of times. Avoid running out of water while steaming as this may damage the plastic bags. Cover the drum with a couple of old blankets and some tarp. Use a rope to make a tight tie around the top of the drum over the covering to keep most of the steam in. It could take about 30 minutes to heat up the water before the steam will appear. I often have the top covering popping up like a mushroom when the steam is pumping. From this time I steam the bags for 4 to 5 hours - the average for a 9 kilogram gas bottle. Once completed, turn of the gas and leave the bags in the drum until cool. This may take up to 24 hours.

A | After Pasteurization - Once your substrate has reached a temperature below 25°C you are ready for inoculations. Carefully break up the seed spawn into individual kernels. Cut open the top corner of the spawn bag with sterile scissors. The easiest way to do the inoculation is by layering your straw and spawn seeds like a sandwich. Add straw in to the bottom of the bag then a bit of seed spawn then again some straw. Proceed until the bag is filled and can be tied closed. Puncture some holes into the sides of your bag to allow airation. Place the inoculated bags in a dark room for 10 - 14 days for the spawn run. You may lay the bags on their sides to avoid the water content to gravitate to the bottom of the bags. Avoid water collecting in the base of the bags. Maintain the temperature throughout at 18ºC.

B | After Steam Sterilization - Once your bagged substrate have reached a temperature below 25ºC you are ready for inoculations. I do this procedure in front of a laminar flow hood in a clean room. If you do not have access to this equipment, you may want to sterilize your space well before inoculation. I use a pre sterilized spoon to transfer seed spawn from one bag to the other. Use a 10% spawn ratio for inoculation. For every 1kg of substrate I will add 100g of grain spawn. TIP: Avoid having all the seed spawn in the top of the bag, work the seed down the inside of the bags by rubbing the bags, the better the seed dispersion at this time, the faster the spawn run will be. Use some filter material in the top of the bags and tape them closed (We use colored tape to separate different batches). The fungus must be able to breathe, so make sure you do not tie the filter in too tight. You can place the bags in a dark incubation room and maintain the temperature at 18ºC. Oyster mushrooms may take a little longer to complete the spawn run when using wood. Wait for the entire substrate to have been covered - the contents will now appear white.

4: Pinning and Maturing your mushrooms

Oyster mushrooms need fresh airlight and some cold days (12ºC - 16ºC) to initiate pinning. This is achieved by placing the mushroom bags in a well-ventilated grow space and piercing the plastic bags (make a X cut). The bigger your substrate bags, the more holes you can make in the plastic. Give your bags 12 hours of light per day to produce well-formed mushrooms. You will first notice minute little knots starting to develop where the bags were punctured. The knots will grow into baby mushrooms and within five days have matured to adults. Oyster mushrooms will produce well in temperatures ranging between 16ºC - 20ºC. Harvest the mushrooms before the cap have curled up. Store your oyster mushrooms refrigerated at 4ºC.

funguys oyster mushrooms

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