Growing Oyster Mushrooms
in buckets

Learn To Grow Oyster Mushrooms with Straw in Buckets

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Why Grow In Buckets?

Growing mushrooms in buckets in a deeply rewarding experience. In this guide we will demonstrate how to cultivate oyster mushrooms in buckets on a simple substrate of sugar cane mulch using cold water lime pasteurisation.

Oyster mushrooms fruit very well from the side making them the perfect candidate for bucket cultivation, additionally they are exceptionally vigorous growing on sugar cane mulch, straw and other similar agricultural products.

Using cold water pasteurisation the straw can be prepared for growing mycelium when gourmet mushroom grain spawn is incorporated. This method allows for large amounts of substrate to be prepared without requiring heat.

how to grow oyster mushrooms in buckets
cold water lime pasteurisation

Pasteurising Straw

It’s important that straw is pasteurised rather than sterilised. Pasteurisation will reduce microorganism populations on the straw without completely eliminating the microbiome of the substrate, this allows the mycelium to fully colonise the substrate.

For pasteurising larger amounts of substrate, cold water lime pasteurisation is generally suitable. However if the straw is old or damp we recommend using hot water pasteurisation.

Can Coffee Be Added?

Fresh coffee grounds can be added to sugar cane mulch & straw as a form of supplementation to increase colonisation times and promote larger yields.

It’s important that the coffee grounds are fresh otherwise they will require pasteurisation.

If growing mushrooms for the first time, it’s recommended to avoid using supplementation as it may increase the chances of contamination forming.

What You'll Need

For this project we used 2 x 20 litre buckets between 1 kilogram of oyster mushroom grain spawn.  You may use the size bucket of your preference. As a general rule we aim to use 10% spawn to substrate but many experienced growers use as low as 2%. Colonisation times and contamination risk will vary accordingly.

  • 4 x 20 litre food grade buckets with lids
  • Sugar cane mulch
  • 2 kg oyster mushroom grain spawn
  • Micropore tape
  • Step drill for maing holes
  • Laundry basket
  • 70L bin
  • Hydrated lime

Step 1. Pasteurise The Substrate

Prepare a lime bath in the 70 L bin using cold waterA. Add approximately 3 grams of lime per litre of cold water used. Pack straw into a laundry basket, apply weight on top and submerge the sugar cane mulch for between 16 – 24 hours.

Once ready, remove substrate from the lime bath and allow it to drain until no excess water drips from the straw when squeezed.

cold water lime pasteurisation
open a mushroom growing kit

Step 2. Prepare The Buckets

The buckets will require holes for ventilation, fruiting and drainage. Holes on the side of the bucket should be within 15 – 20 cm of each other to allow for fresh air exchange. 

A few holes must also be made on the base of the bucket. As the mycelium matures it will release yellow, liquid metabolites which will need to drain away.

Apply micro pore tape to the holes on the outside of the bucket. Micro pore tape will help retain moisture while allowing for fresh air exchange. 

Step 3. Fill Buckets

Using the recently pasteurised and drained sugar cane mulch, fill the buckets. Add layers of sugar cane mulch and grain spawn throughout. These layers can be mixed together for a more uniform colonisation if preferred.

We use a minimum of 500 grams of grain spawn per 20 L bucket. Less spawn will colonise slower and therefore be at greater risk of contamination.

Pack firmly, but not too firmly. Ensuring that the substrate can still breathe. Place lid on the bucket and mark with date and species.

Step 4. Allow To Colonise

The mycelium will colonise the substrate during the next 2 to 3 weeks. Feel free to check on it occasionally and you will notice the white growth. It’s normal if your substrate begins to produce yellow droplets. These are metabolites and are a by-product of the mycelium.

Pay attention for signs of growth. The primordia will bulge and begin to push off the micropore tape once it’s ready to fruit.

Step 5. Place In Fruiting Conditions

Oyster mushrooms can be very forgiving. By growing in buckets we can easily provide the conditions to trigger fruiting. Once the fruits are forming we just need to assist in maintaining humidity. 

I recommend storing your mushroom bucket away from direct winds, out of direct sunlight and where it can stay moist. A greenhouse, basement, bathroom or dark corner in the garden can all be suitable locations. Experiment and see what works for you in your climate. 

You can mist them a few times each day to help with keeping them moist or alternatively you can use a cheap humidifier to help automate the process and ensure consistent results.

This 6 litre humidifier works perfectly in our mini-greenhouse. It’s cheap and very effective. Before I would spray the walls of my greenhouse 2 -3 times a day to grow consistently stunning oyster mushrooms. Now even during the driest months it keeps my mushrooms growing their best.

Step 6. Harvest

Harvest the oyster mushrooms before their caps begin to turn upwards. It’s at this point they will drop the majority of their spores and begin to lose condition. 

Store them in a paper bag in the fridge for optimum shelf live.

The bucket will require some time to rest and recuperate before producing the next flush of mushrooms. Moisten substrate and return to cover holes with micro pore tape.

Each subsequent flush is usually smaller. In ideal conditions I generally expect to produce the same weight in fresh mushrooms as the weight of the dry substrate used. Species like pink, white and blue oyster may yield more while yellow oyster tends to yield less.

Using A Humidifier

Humidity can be managed through a diligent misting and fanning regime, however the introduction of a humidifier and humidity controller can help automate the process and ensure consistency.

Adding a 6L humidifier and controller to a greenhouse with the addition of a USB fan is a quick and easy way to make a low cost fruiting chamber that delivers excellent results.

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