Cultivating Mushrooms on Straw: How to Treat the Straw Right

Cultivating Mushrooms on Straw: How to Treat the Straw Right

Any process of cultivating mushrooms involves media treatment, and today we are sharing about the process of using straw to grow mushrooms

Cultivating mushrooms on straw involves various ways of treating the media. A few years ago we used a SAR grant to study different methods for growing oyster mushrooms on straw.

The process of cultivating mushrooms on straw is really great for doing at home. It’s easy, it’s fast, and it can produce high-quality mushrooms.

The treatment methods we studied for cultivating mushrooms on straw

  • Lime and wood ash
  • Fermentation
  • Pasteurization

Note: Steam is also an option for treating your mushroom substrate, but we did not test this one during the research.

Before getting into the various methods for cultivating mushrooms, let’s address the straw. The straw should be chopped up. Straw in bales is typically 12” long, but an ideal size for us is 2”-3”. This way it is finer, it can be packed more tightly, and the mushroom mycelium can access the straw a lot more easily.

Additionally, it’s important to differentiate between straw and hay. Straw does not have developed seed heads present whereas hay does. This is important because seeds are very dense in nutrients. If you want to use any of the first three treatment methods (lime/wood ash, fermentation, or pasteurization) then you want low nutrient materials. The seed heads will lead to contamination in the process.

Cultivating mushrooms with lime

Use hydrated lime with under 10% magnesium because magnesium prohibits mycelium growth.

We add the lime to the water, which increases the pH of the solution to 12 or 13. This pH level will burst the cell walls of the micro-organism, allowing a clean palette for the mushroom mycelium to grow out into.

We use one gallon of hydrated lime to fill one 55 gallon drum of chopped straw. Combine the straw with the lime and water and make sure all of the straw is covered. You will want to soak the straw for 16 hours in the lime solution.

Cultivating mushrooms with wood ash

The process is exactly the same as listed above for the lime, but the lime is substituted out for wood ash instead. This is perfect for anyone with an abundance of wood ash that may have come from burning wood during a long, cold New England winter.

Cultivating mushrooms with fermentation

Also referred to as “stinky straw”, this is a 3-7 day submergence in water.

You begin by chopping the straw and putting it in a burlap sack that you then submerge in water. You will know when it’s ready because it will smell strongly. The time it takes to ferment will depend on the temperature. If you’re in a hot location, the fermentation will take quicker than if it’s cold.

This process led to the lowest yields for us. It is best done with a high inoculation rate of aggressive strains.

Cultivating mushrooms with pasteurization

In this process we keep the straw substrate heated between 145 - 175 degrees Fahrenheit for two hours. This method us used frequently in cultivating mushrooms. It can be done with a variety of strains with a variety of substrates. It is known for good yields.

The downsides: It can take a long time, and it uses a lot of propane fuel.

The image to the right shows our results from the test. As you can see, lime was consistently a good option. Pink oyster did really well on wood ash, although most other mushrooms did not. This is likely due to the fact that pink oyster is an aggressive strain.

Do you want to start cultivating mushrooms at your own home, in the garden, or as a commercial mushroom farmer? We have a variety of options for you. Check out our mushroom spawn options and our mushroom growing kits!

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