So you want to learn how to grow Oyster mushrooms? They are crazy delicious and one of the most straightforward varieties of mushrooms to grow, and super healthy for you.
Oyster mushrooms are possibly the easiest variety of mushrooms to grow, ready to harvest just seven days after starting to grow out of the bag and harvested three times with a new crop of mushrooms manifesting every 7-14 days.
Growing Oyster Mushrooms
The most common materials to grow Oysters on are freshly cut hardwood logs or shredded straw. Growing mushrooms on logs will take up to a year for your first harvest. Growing on straw requires you to pasteurize the straw first to kill off resident micro-organisms that will compete with your mycelium.
This is where coffee comes in. The beauty of growing mushrooms on fresh coffee waste is that the coffee brewing process already pasteurizes the substrate, so you can bypass the whole pasteurizing step and move straight into the inoculating.
Get Prepared
Once you’ve decided you want to learn how to grow Oyster mushrooms, the next step is to get prepared & source all your materials.
Before you can do this, you’ll need to decide which oyster mushroom strain to grow and which substrate you’ll grow on.
Decide Which Oyster Mushroom Strains To Grow
There are several different types of Oyster mushrooms to choose from. Here are some of the more popular ones.
- Pearl Oyster Mushroom (Pleurotus ostreatus)
Also sometimes called the common Oyster mushroom, winter Oyster mushroom, or grey Oyster mushroom. The Pearl Oyster Mushroom is one of the most commonly available varieties. They grow best in colder temperatures.
- Blue Oyster Mushroom (Pleurotus ostreatus var. columbinus
Commonly found throughout the Northern hemisphere and a subspecies of the common Oyster, the Blue Oyster Mushroom is one of the fastest colonizers of all the Oyster mushroom varieties and prefers growing in cooler temperatures of 12-18 C (45-65 F).
- Phoenix Oyster Mushroom (Pleurotus pulmonarius)
It is also sometimes known as the Summer Oyster mushroom, Italian Oyster mushroom, or the Indian Oyster mushroom. This variety has evolved to grow in warmer climates and depending on the strain is either white or a brown/tan color.
- Golden Oyster Mushroom (Pleurotus citrinopileatus)
Sometimes also called Yellow Oyster mushrooms, this variety is best known for its’ fantastic color and looking similar to the popular Chanterelle mushroom. They prefer warmer temperatures of 18C-30C (64-86F).
- Pink Oyster Mushroom (Pleurotus djamor)
One of the most striking of the Oyster mushroom varieties, the Pink Oyster mushroom grows really fast, producing fruits in as little as 3-4 weeks. They prefer warmer temperatures of 18C-30C (64-86F).
- King Oyster Mushroom (Pleurotus eryngii)
Also known as the Eryngii mushroom, it has a firm texture and delicious meaty flavor. It is more challenging to cultivate than other Oyster mushrooms, and so is not the best variety to get started with. It prefers cooler temperatures between 12C-18C (45-65 F).
Decide Which Oyster Mushroom Substrate To Grow on
Substrates are the food source that enables the growth of mycelium.
Mycelium is the root-like vegetative growth of the fungus and is critical to the cultivation of Oyster mushrooms in the same way an apple tree is to an apple.
The most widely used substrate for Oyster mushrooms is straw. However, sawdust, cardboard, coffee grounds, and other byproducts of agriculture such as sugarcane bagasse and cotton waste can also be used.
The easiest substrate to get started with is probably wood pellets as they come already pasteurized and you just need to add water to hydrate them. Straw is also a very forgiving substrate to grow on.
Either way, choose a substrate material that you can easily source and use the instructions below to prepare it for inoculation.
Order Your Supplies
The last step is getting your supplies ready so you can get started.
You’ll need to order:
- Oyster mushroom spawn (at least 100g, but preferably 1kg or more)
- Your substrate material
- Either make or purchase growing bags/containers
Grain spawn will produce bigger yields than sawdust spawn, so try to source this if you can.
As for growing containers, ideally you’ll get hold of purpose-made mushroom cultivation bags. They enable the perfect air exchange and keep out competitors.
Mushroom cultivation bags with breathable filter patch. If you can’t source these growing bags, you can also grow mushrooms in a bucket, or use large freezer or ziploc bags with 0.5mm holes poked in every 10 cm around the bag.
Prepare Your Oyster Mushroom Substrate
The substrate’s goal is to provide a hydrated nutrient-dense food source that is also clean of other microorganisms that would normally compete with the mushroom mycelium.
Straw, cardboard, sawdust pellets and coffee grounds are all easy substrates to use for growing Oyster mushrooms that achieve this goal.
Here’s a quick overview of how to prepare each one.
Straw & Cardboard
Straw is the most commonly used substrate for Oyster mushroom cultivation. It is usually cheap, contains essential nutrients and Oyster mushrooms thrive on it.
Pasteurise by soaking in hot water (65-80C / 149-176 F) for 1-2 hrs, or in a cold water high-pH lime bath for 12-18 hours
Sawdust Pellets
The great thing about using these is that they are already pasteurised by the heat & pressure of pellet production process. Add equal weight of water to weight of pellets, soak for 30 mins. And then mix to break up the pellets into hydrated sawdust.
Coffe Grounds
Waste coffee grounds – a plentiful (and already pasteurised) resource
The key is to only use fresh grounds (within 24 hours of brewing) which are already pasteurised and hydrated by the coffee brewing process. Beyond 24 hours, competing molds start to develop and will out compete your mycelium.
You’ll need enough to fill the bag or container you are using two-thirds full, and the grounds need to be fresh that day. (within 24 hours whilst it’s still fresh) Ideal as a substrate on its own in small amounts (1kg or less), but mix in 20-50% of straw if you go bigger.
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Inoculating
Firstly order your spawn in. You’ll have greater success if you use a high spawn: coffee grounds ratio. To begin with, I’d recommend using around 500g of oyster mushroom spawn to each 2.5kg of spent coffee grounds.
If the vendor you purchase the spawn from also sells filter patch grow bags, get one of these too. They will increase your chance of success by reducing contamination and providing the perfect growing environment inside the bag.
You can try using a large 2 litre freezer bag, empty ice-cream tub or milk carton – cleaned out well, and with 4 x 5mm holes cut in the sides.
Wash your hands and lower arms well and mix your spawn into the bowl, evenly throughout the coffee. Load the mixture into your cultivation bag or container and close it up tight, ensuring you have cut the 4 air holes if you do not use the filter patch bags.
Depending on the material, you are aiming for anything between 55% hydration (sawdust and coffee grounds) to 74% (straw).
Next, mix the substrate and mushroom spawn in a container of some sort (large plastic box, barrel, whatever you have to hand) then load the substrate into your growing vessels and close the top with a rubber band, paperclip, tape or tie of some kind.
Spawn Run
Place your bag/container in a warm (64 – 77°F, 18C – 25°C) and dark place (airing cupboard, under a bed, in a cupboard in a heated room etc). During the next three weeks, you will see the spawn come to life and grow across the coffee grounds – turning the whole mixture white by the time it has fully colonized the mixture.
Fruiting
Once the growing medium is fully colonised by the spawn, it is time for the mushrooms to start fruiting.
Mushrooms grow in the wild in response stress (like running out of food) or to changes in their environment.
You want to replicate this process in your home or garden. This signals to the mycelium that it’s time to start producing mushrooms and small pins begin to emerge.
Once the bag is fully colonised (i.e the mycelium is soon going to run out of food) it will now be keen to grow mushrooms in a bid for survival.
All you need to do is provide the optimal conditions for the mushrooms to develop:
- Place it in a spot with plenty of fresh air and a little light – a shaded windowsill or worktop is ideal. Cut a 5cm x 5cm (2in x 2in) hole in your bag/container and spray this area twice daily with water, trying not to allow it to dry out. Mushrooms love damp, humid conditions, and they will outright refuse to grow if it’s too dry.
Light
While direct sunlight is not a good idea, some indirect or shaded light is needed for the fruitbodies to form properly. They don’t gain energy from the light, so an indirect lighting source or shaded windowsill will be sufficient.
Fresh Air
In the wild Oyster mushrooms are used to growing out of a stump or log in fresh oxygen rich air. Providing a 5cm slit or hole in your bag will signal to the mycelium that there is a space to grow out from.
Humidity
Spray with water twice a day to keep the substrate hydrated and the environment in which the mushrooms are developing, humid. This will encourage the mushrooms to form and stop them from drying out as they develop.
Temperature
This is specific to each strain, but generally (with the exception of King Oysters) most Oyster mushroom strains are not too fussy about what temperature they will grow at. They will form best in their ideal range as mentioned in the strains info above, but as long as it is in the range of 10-30C (50-86F) they should still fruit.
After a week or so, you will start to see tiny little mushrooms bursting into life. Over the following 5-7 days they will double in size every day.
After 3 weeks, your whole bag/container of the coffee and spawn mixture should now look completely white.
Common Problems During Fruiting
- The drying out of your substrate and or mushrooms (Yellow or brown appearance. Just spray more regularly if you see this
- Long thin Oyster mushroom stems indicate high Co2.Open the window a couple of times a day to increase oxygen
- If you see any areas of green, this is a competitor mold. If it is just a small patch, you can try adding a little salt to the area which should kill it off and still allow the mushroom mycelium to prosper.
- If the whole bag has gone green, then it will most likely be caused by poor quality spawn, or by a lot of mold spores having been mixed in with the coffee grounds somewhere along the way.
Harvest & Growing More Crops
Once the edge of the caps of the Oyster mushroom starts to flatten out or turn upwards, it’s time to harvest before they begin dropping lots of spores.
A couple of tips: if you see them stop growing any bigger, starting to dry out, or dropping lots of white ‘dust’ (spores) then it is time to harvest!
You can either twist them off with your hands or cut the cluster off with a knife.
Two days later, submerge the mushroom substrate in water overnight to rehydrate, then follow all the same instructions
- Spray twice a day in the same hole you cut out earlier, and 1-2 weeks later you’ll have more mushrooms beginning to emerge.
- You can repeat this for a smaller 3rd crop before the substrate starts to run out of available nutrients.
Enjoy your yummy Oyster mushroom harvest! Try out different recipes either from our website or other like Martha Stewart.
