What is Mushroom Spawn?
Mushroom spawn is sterilized grain such as rye, milo, or millet inside a jar or bag that has been fully colonized by mycelium after injecting it with a mushroom spore or liquid culture syringe. Once the mycelium has taken over the entire bag, it becomes grain spawn, which is then mixed with a bulk substrate to continue the growing process and eventually produce mushrooms.
Why Use Grain Spawn?
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Highly Nutritious – Provides the essential nutrient base and water content for spore germination.
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Compatible with Various Mushroom Species – Works well with gourmet, medicinal, and dung-loving mushrooms.
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Simple to Scale Up – One colonized spawn bag can be divided into additional sterile grain bags to increase the total amount of useable spawn.
Because of its efficiency, reliability, and versatility, grain spawn is the industry standard for cultivating mushrooms. The best grain for mushroom spawn is milo or millet, as their small size provides more inoculation points than larger grains like rye, allowing for faster colonization.
What is Mushroom Substrate?
While grain spawn supplies nutrients, mushroom substrate provides a hydrated base for the mycelium to expand out and produce mushrooms. The substrate’s main job is to supply the mycelium with water and a larger surface area, which is necessary for growth.
Fun fact: Mushrooms are made up of 90% water!
Popular Types of Mushroom Substrate
Different substrates are suitable for different types of mushrooms. The most common choices are:
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CVG Substrate – A blend of coco coir, vermiculite, and gypsum (CVG), which is a cost-effective option with excellent moisture retention and structure, making it one of the most widely used substrates.
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Manure-Based Substrate – Often used for dung-loving species but requires more intensive pasteurization to remove contaminants.
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Hardwood Sawdust & Chips – Used for wood-loving mushrooms like oyster, lion’s mane, and shiitake.
Mushroom Spawn vs. Mushroom Substrate: Key Differences
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Growing Medium |
Mushroom Spawn |
Mushroom Substrate |
|
Purpose |
Provides nutrients and mycelium for growth |
Provides a hydrated base for expansion and fruiting |
|
Material |
Milo, millet, rye |
CVG, manure, sawdust |
|
Stage in Growth |
Used in the gemination and first colonization phase |
Used for mycelial expansion and fruiting |
|
Sterilization |
Fully sterilized to prevent contamination |
Usually pasteurized (some are sterilized) |
|
How It’s Used |
Inoculate with spores or liquid culture |
Mixed with fully colonized grain spawn inside a monotub or grow bags for fruiting |
How to Use Mushroom Spawn and Substrate Together
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Inoculate the Grain Spawn – Use a syringe to inject a liquid culture or spore solution into a mushroom grain bag with a self-healing injection port.
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Colonization – Allow the mycelium to spread throughout the grain. Keep the bag in a clean area, away from direct sunlight, maintaining a temperature in the mid-70s to low 80s for the fastest colonization. This process usually takes 7-21 days.
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Transfer to Bulk Substrate – Once fully colonized, break up the grain spawn and mix it with bulk mushroom substrate inside a monotub or mushroom grow bags.
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Incubation – Allow the mycelium to fully take over the substrate at a steady temperature in the mid-70s, ensuring consistent moisture levels. No need for complete darkness—just avoid direct sunlight.
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Fruiting – Introduce fresh air exchange to the growing chamber and indirect sunlight. Within a week or two, you’ll see mushrooms start to form!
Choosing the Right Supplies for Your Grow
Using high-quality, contaminant-free materials is key to a successful grow.
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For new growers, pre-sterilized grain spawn and pre-pasteurized substrate bags offer the easiest and quickest way to start growing mushrooms.
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For bulk growers, buying bulk mushroom substrate and grain spawn in larger quantities from a vetted vendor saves time, money and ensures consistent results.
For a hassle-free experience, check out our complete mushroom grow kits, which include sterilized grain bags, and pasteurized bulk substrate. With everything you need in one package, you can skip the prep work and jump straight into cultivation.
Looking for grain or substrate separately? We also offer sterile grain bags and bulk mushroom substrate for a custom growing experience.
Final Thoughts
Mushroom spawn and substrate are both essential for a successful grow, but they have different roles in the growing process. Grain spawn provides the nutrients for germination and colonization, while Substrate provides the structure and moisture content necessary for fruiting. Whether you're growing gourmet or medicinal mushrooms, using high-quality spawn and substrate will set you up for success.
Get started today and grow with confidence!
