Substrate for Mycology: A Comprehensive Guide on Straw

Dive deep into the world of straw-based substrates, a pivotal element in the mycological realm that bridges the connection between fungal spores and prolific fruiting.

While many think of mycology as a field reserved only for seasoned experts, the beauty of this discipline lies in its accessibility. Straw-based substrates, for instance, offer both budding enthusiasts and seasoned mycologists an approachable yet nuanced medium to cultivate various mushroom species.


Welcome to a living guide, where we constantly update and refresh our content based on new findings, feedback, and practices. As you embark on this journey, you’ll discover essential materials, a breakdown of ingredients, and intricate procedures, all aimed at empowering you with unparalleled substrate knowledge.


  • Straw (chopped or shredded)
  • Water
  • A large pot or pressure cooker
  • Pint or quart-sized mason jars with lids
  • Gypsum (optional, yet beneficial)
  • Karo syrup (optional, but aids nutrition)
  • Thermometer
  • Measuring cup and spoons

Straw TEK Quick Reference Chart:

Gypsum5g (optional)10g (optional)
Karo Syrup5ml (optional)10ml (optional)
Pressure Cooking Time90 Minutes90 Minutes
Pressure Cooking PSI15 PSI15 PSI
Note: Gypsum and Karo syrup are optional, but they enhance texture and nutritional content.


Preparation of Straw:

  • Begin by taking bundles of straw and, using gardening shears or a sharp knife, cut them into smaller pieces.
  • Aim for lengths between 2-4 inches. These smaller sizes allow the mycelium to colonize the substrate more efficiently.

Incorporating Gypsum:

  • If you decide to incorporate Gypsum, spread your chopped straw out on a flat surface. Sprinkle the Gypsum evenly over the straw, ensuring a thorough mix.
  • This addition provides the straw with improved structure and moderates the pH level to create an ideal environment for mycelium growth.

Soaking Process:

  • Transfer the straw (and gypsum mixture, if used) to a large pot or container.
  • Fill it with enough water to submerge the straw completely. Allow it to soak for a full 24-hours. This soaking period ensures that the straw is fully saturated, making it a receptive substrate for colonization.

Draining Excess Water:

  • Once soaked, place the straw in a colander or a mesh bag, allowing water to drain off.
  • It’s crucial to ensure that the straw is moist but not dripping wet, as overly wet substrates can lead to contamination.

Adding Karo Syrup:

  • If you opt to use Karo syrup, pour the designated amount over the damp straw.
  • Mix thoroughly, ensuring even distribution. This carbohydrate-rich syrup serves as an additional food source for the mycelium, boosting its growth.

Jar Packing:

  • Filling: Load the jars with the Straw mixture with the correct amount of Straw (See Recipe).
  • PLEASE NOTE: Ensure you leave about a 1-inch gap at the top to facilitate room, ensuring there’s enough headspace for air exchange and to prevent jar overflow as mycelium grows.
  • Securing Lids: When placing the lid, ensure the rubber seal faces upward. This helps prevent the jars from getting vacuum-sealed during the sterilization process. Another option is to use a mycology lid such as one that contains a filtered vent and/or injection port (we have articles, DIY Supplies, and both Free & Paid for Mycology Courses hosted on our 🍄 Mushroom Academy!
  • Foil Cover: Wrap the tops of the jars with aluminum foil. This provides an added layer of protection against potential moisture intrusion during pressure cooking.


  • Using a pressure cooker, place a cloth or metallic stand at the base to prevent the glass jars from direct contact with the cooker’s bottom.
  • Arrange the packed jars inside. Set the pressure cooker to 15 PSI and let it run for 90 minutes. This step is crucial to kill off any potential contaminants.

Cooling Phase:

  • After the sterilization process, turn off the heat and allow the pressure cooker to cool down naturally.
  • Once it reaches room temperature, the jars can be safely removed and are ready for inoculation.

Remember, each step is integral to the success of your mycological endeavors. The universe of mushrooms is expansive, each variant bearing its own unique charm and characteristics. The Marketplace on the 🍄 Mushroom Network is a testament to this diversity. It is a haven for those seeking a deeper understanding of the magical world of mushrooms. If you’re keen on learning more about this type of mushroom and other mushroom variants, this Marketplace is your ultimate resource.


  • Straw Size Matters: The uniformity achieved by chopping straw to 2-4 inch lengths ensures consistent colonization. Larger chunks may not be fully colonized and could become a hotspot for contamination.

  • Watch The Clock: Avoid soaking straw beyond the 24-hour recommendation. Excessive soaking can lead to a breeding ground for unwanted bacteria and mold.

  • Nutritional Boosters: The use of gypsum and Karo syrup isn’t mandatory, but they can significantly enhance your substrate. Gypsum improves substrate structure while Karo syrup provides extra carbohydrates for the mycelium, which can lead to a quicker colonization phase.

  • Sanitation is Key: Always prioritize cleanliness. Before starting your procedure, disinfect your work area and ensure you have clean hands or gloves. It reduces the risk of introducing contaminants to your substrate.

  • Experimentation for Experienced Mycologists: Those well-versed in mycology might consider blending straw with other organic materials like wood chips or coffee grounds. Finding the perfect ratio can significantly improve growth rates and yields, depending on the fungal strain being cultivated. Always document your mixes and results for future reference.

Not sure where to start? The 🍄 Mushroom Academy shines a light on this Straw substrate TEK and countless others, simplifying complex procedures into digestible lessons. From novice forays into mycology to expert-level dives, our 🍄 Academy harbors courses tailored to every individual’s pace and preference. Discover how we make substrates, genetics, and advanced techniques feel like second nature. Join us, and cultivate not just mushrooms, but a lifelong passion. Whether you’re a beginner eager to learn or an experienced mycologist looking to broaden your knowledge, the 🍄 Academy has something for everyone.

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Embarking on the mycological journey is akin to opening a door to a world teeming with mysteries, innovations, and discoveries. The 🍄  Mushroom Network stands by your side, ready to guide, educate, and supply. Whether you’re poring over our in-depth articles, joining a course at our 🍄 Mushroom Academy, or procuring the finest mycology supplies, we’re here to ensure your success. Together, let’s cultivate knowledge, passion, and a thriving community.

Don’t forget to check out the 🍄 Mushroom Network’s Marketplace to see what’s available. But hurry, our shelves are constantly evolving, and you wouldn’t want to miss out on this wonderful mushroom. Join our growing network of Patrons, Genetics, and Mycologist Vendors only on the 🍄 Mushroom Network!

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