How To Create Fruiting Blocks For Wood-Loving Mushrooms

Share This Post

For fungi enthusiasts and mycophiles, cultivating wood-loving mushrooms at home can be a deeply satisfying and rewarding experience. In this blog post, we’ll delve into the intricacies of making fruiting blocks for wood-loving mushrooms using a master mix. By the end of this post, you’ll have all the knowledge you need to embark on your mushroom cultivation journey.

What are Fruiting Blocks?

Fruiting blocks are essentially the growing medium that provides the nutrients and conditions necessary for wood-loving mushrooms to grow and fruit. These blocks are typically composed of a mixture of hardwood sawdust, supplemented with organic materials such as bran or soy hulls, and gypsum. The mixture is then sterilized, inoculated with mushroom spawn, and sealed in a breathable plastic bag to create the ideal environment for mushroom growth.

Choosing Your Mushroom Species

There are countless wood-loving mushroom species that you can choose from for cultivation. Some popular options include:

  1. Shiitake (Lentinula edodes)
  2. Oyster (Pleurotus spp.)
  3. Lion’s Mane (Hericium erinaceus)
  4. Maitake (Grifola frondosa)
  5. Reishi (Ganoderma lucidum)

Each species has its own specific requirements for temperature, humidity, and light conditions, so make sure to do your research before selecting a species to cultivate.

Creating the Master Mix for Our Fruiting Block

To make fruiting blocks for your chosen mushroom species, you’ll need to create a master mix. This mix provides the ideal balance of nutrients and structure for mushroom mycelium to colonize and fruit. Here’s a basic recipe for a 5 pound fruiting block:

  1. Hardwood sawdust pellets: 2.5 cups
  2. Soy hull pellets: 2.5 cups
  3. Distilled water: 1.4 liters
  4. Mushroom grow bag. 8 X 5 X 20. 0.2 Micron filter patch. 6 mil polypropylene
  5. Pressure cooker or canner

Fruiting Block Instructions

  1. Weigh out the appropriate amounts of hardwood sawdust pellets, Soy hull pellets, and water.
  2. Mix the ingredients thoroughly in a large container, ensuring that the mixture is evenly distributed.
  3. Carefully place your mixture into a grow bag trying your best not to get contents on the filter.
  4. Fold the grow bag with the masters mix over the top and tuck it underneath the bag. The opening of the grow bag should be closed due to the weight of the block on top.
Pre sterilized Fruiting blocks
Example of a fruiting block pre-sterilized

Fruiting Block Sterilization

Before inoculating the master mix with mushroom spawn, it’s essential to sterilize the mixture to kill any potential contaminants. This can be achieved using one of the following methods:

  1. Autoclaving: If you have access to an autoclave, load the master mix into autoclavable filter patch bags and sterilize at 15 PSI for 2-2.5 hours.
  2. Steam sterilization: For those without access to an autoclave, steam sterilization using a pressure cooker is a viable alternative. Pack the master mix into filter patch bags, fold the bags into the block formation. This can be done by pinching the sides of the bags and folding the top of the bag over itself. The weight of the bag should keep bag closed throughout the sterilization process. Finally, place the bag in the pressure cooker. It is recommended to raise the bag via a stand so that it is not directly in contact with the water. Follow the manufacturer’s instructions for sterilization, typically requiring 15 PSI for 2-2.5 hours.

Allow the sterilized substrate to cool to room temperature before proceeding to the inoculation step.

Fruiting Block Inoculation

For this step, you’ll need mushroom spawn, which can be purchased from a reputable supplier or cultivated from spores or tissue samples. Learn how to make your own grain spawn jars!

  1. Prepare a clean, sterile workspace. Wipe down surfaces with a 10% bleach solution, and wear gloves and a face mask to minimize contamination risk.
  2. In a still air box, laminar flow hood, or in sterilized open air, open the sterilized master mix bags and the mushroom spawn.
  3. Add the spawn to the master mix, using a ratio of 1:10 (spawn to master mix). One full quart jar of spawn should suffice for a five pound fruiting block.
  1. Seal the inoculated bags or jars, either by folding and taping the bag tops, using an impulse sealer. Follow the directions per the impulse sealer’s manufacturer instructions.
  2. Mix the spawn and the substrate so that the spawn is evenly distributed. Next fold the bag similar to the pre sterilization process. This allows the mycelium to grow and spread uniformly.
  3. Label each bag with the mushroom species and inoculation date to keep track of the progress.
Created fruiting block
A fruiting block that has just been sealed. Still needs to be mixed and formed into a block.
Completed fruiting block.
The finished product!
Blue oyster fruiting block
Blue oyster mushrooms grown from the fruiting block pictured above.


Cultivating wood-loving mushrooms using fruiting blocks and a master mix can be a fulfilling and rewarding endeavor. With patience, attention to detail, and adherence to the proper techniques outlined in this blog post, you’ll be well on your way to enjoying your very own home-grown mushrooms. Happy cultivating!

Subscribe To Our Newsletter

Get updates and learn from the best

More To Explore

Do You Want To Learn More?

drop us a line and keep in touch