Grain Spawn vs. Sawdust Spawn — What’s the Difference?

When you’re first learning to grow mushrooms, it’s easy to get confused by the different types of “spawn.” Two of the most common are grain spawn and sawdust spawn. Both are just ways to spread mushroom mycelium so you can grow more mushrooms, but they behave differently and suit different projects.

Let’s go through what each is, how to use them, and which one makes sense for your setup.

What Is Spawn?

Spawn is any material that’s been colonized by mushroom mycelium and is ready to inoculate a new substrate. Think of it as the “seed” that spreads the mushroom network.

Using spawn speeds up your grow, reduces contamination risk, and gives your mushrooms a strong start compared to using spores alone.

Grain Spawn

What it is: Sterilized grain (rye, wheat, oats, millet, corn, etc.) fully colonized with mycelium.

Why growers love it:

• Fast colonization: Grains are nutrient-dense and mycelium runs through them quickly.

• Breaks apart easily: You can shake or crumble jars/bags so every kernel becomes a new inoculation point.

• Scales easily: You can go from a single jar of grain spawn to many bags/tubs of bulk substrate.

Typical uses:

• Indoor gourmet mushrooms (oysters, lion’s mane, shiitake on supplemented blocks).

• Expanding to more grain (“grain to grain” transfer).

Things to know:

• Grains require proper sterilization and clean handling or contamination can happen.

• Slightly more prep and equipment if you make your own (pressure cooker, jars or bags).

Sawdust Spawn

What it is: Hardwood sawdust (often with a little bran) colonized with mycelium.

Why growers use it:

• Stable and less contamination-prone: Sawdust has lower nutrients than grain, so contaminants spread slower.

• Great for wood-loving mushrooms: Perfect for outdoor logs, garden beds, and commercial plug spawn.

• Low maintenance once colonized: Stores well and handles outdoor conditions better than grain.

Typical uses:

• Outdoor mushroom beds and log inoculations.

• Shiitake, lion’s mane, and oysters grown off logs or hardwood blocks.

Things to know:

• Colonization is usually slower than grain.

• Harder to break apart and mix evenly.

• Not ideal if you’re doing lots of indoor bulk grows.

Side-by-Side Comparison

Which Should You Choose?

• Indoor & fast production: Go with grain spawn. It’s easy to use, fast, and perfect for bulk substrates like coco coir or sawdust blocks.

• Outdoor, long-term projects: Choose sawdust spawn — more stable and better for logs, wood chips, or garden beds.

💡 Tip: Many growers start with grain spawn to build volume and then transfer to sawdust spawn if they’re moving outdoors.

Where to Get Spawn & Gear

• Buy pre-made grain spawn:

• Buy premade sawdust spawn

• Make your own: Once you’re ready to DIY, my [LC/agar/substrate ebook] shows how to create your own clean grain spawn at home.

Final Thoughts

Both grain and sawdust spawn work — it just depends on where and how you want to grow. For most beginners growing indoors, grain spawn is the easiest and fastest option. If your goal is outdoor logs or a more stable starter for long-term use, sawdust spawn is the way to go.

This post may contain affiliate links. If you make a purchase through these links, I may earn a small commission at no extra cost to you. I only recommend products and gear I personally use or trust.