8-Pack Organic Sterilized Grain Spawn Bags

€112,95

Each spawn bag contains our proprietary blend featuring hydrated, nutrient-rich, organic millet and wheat berries. Bags also include a self-healing injection port for use with a spore or culture syringe plus a 0.2 micron filter patch to block airborne contaminants while providing even gas exchange.

Add Bin Liners + ($14.99)

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Monotub liners

Monotub liners

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monotub-supplies

sterile-grain-spawn-bags

sterile-substrates

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In Stock. Ships in 2-5 business days.

Trusted by 350K+ Growers

Trusted by 350K+ Growers

Money Back Guarantee

Money Back Guarantee

USDA Certified Organic

USDA Certified Organic

Successful mushroom cultivation begins with a foundation of premium, sterile grain spawn. North Spore's 8-Pack Organic Sterilized Grain Spawn Bags are meticulously prepared to provide a reliable and contamination-free starting point for your mycelial projects.

Each bag is USDA Certified Organic, ensuring a clean and natural substrate free from unwanted chemicals. Our state-of-the-art sterilization process, conducted in an ISO 7 laboratory environment, guarantees optimal conditions for rapid and healthy mycelial colonization.

This convenient 8-pack offers ample sterile grain for scaling your cultivation efforts, whether you are a hobbyist or preparing for larger batches. The high-quality grain substrate supports vigorous mycelial growth, setting the stage for abundant flushes.

Designed for indoor growers, educators, and mycology enthusiasts, these grain spawn bags are ideal for inoculating bulk substrates in monotubs or other controlled growing systems. They integrate seamlessly with North Spore's range of cultivation tools.

Rely on North Spore's scientific expertise and commitment to quality for a robust start to your mushroom growing journey. For best results, follow recommended inoculation procedures and environmental controls.

Why Millet?

Millet has a much lower endospore load than rye and wheat, making it less prone to contamination. And its small size means your spawn will have many more inoculation points for the same volume of grain. By using millet, the mycelium will spread more evenly and abundantly through the substrate. And, as a high-nutrient medium, it also encourages rapid mycelial expansion.

Made Right, Guaranteed
  • Sterilized in a commercial-grade autoclave for consistent results
  • Multiple bags from every batch tested in our state-of-the-art lab
  • Verified using biological indicators and temperature sensors
  • Backed by our 100% Guarantee — if it’s not sterile, we’ll make it right
How to Use

Spawn to bulk ratio

We recommended mixing 1 colonized grain spawn bag with 2-3 bags of sterile substrate. (Higher inoculation rates may improve your success.) 

Best Practices

We recommend clean hands, latex or nitrile gloves, and sterile technique when using sterile substrate to reduce the introduction of contaminants.

Be sure to mix colonized grain spawn thoroughly into your substrate. 

It is best practice to wait a minimum of 1 week after arrival before using sterile substrates to ensure they were not compromised during transit. Rest assured that your purchase is 100% guaranteed. If your substrate was compromised, we will replace it.

Storage

Sterile substrates should be stored at room temperature out of direct sunlight. No refrigeration is necessary. They can also be stored for several months before use.

Notice

North Spore's products shall be used only for lawful purposes. North Spore does not condone Psilocybin (Psilocybe cubensis) or hallucinogenic (magic) mushroom growing in jurisdictions where it is currently illegal.

CA Prop 65 Notice

Grow Right
"Boomr Bin" Monotub
"Boomr Bin" Monotub (+€26,95)

The best grow chamber for bulk substrate

NocBox Still Air Box
NocBox Still Air Box (+€65,95)

Reduce contaminants when you mix or inject substrate

Syringe Multiplier & LC Kit
Syringe Multiplier & LC Kit (+€23,95)

Multiply any spore or syringe into 30 syringes!

8-Pack Boomr Bag
8-Pack Boomr Bag (+€112,95)
Nitrile Gloves
Nitrile Gloves (+€12,95)

Stay clean, stay sterile

Sterile Substrate FAQs

Choose Boomr Bag for massive flushes of dung-loving species, CVG for versatile bulk grows and great moisture retention (great for beginners), and Wood-Lovr for wood-loving species like oysters, lion’s mane, and reishi. Each is optimized for the best yield and growth rate in its category.

Keep bags at room temperature and out of direct sunlight. Substrates can be stored for several months, and grain bags should be used within a few weeks for best results.

We sterilize our products in commercial autoclaves and test every single batch for bacterial growth so you know the product is sterile when you receive it. And if the bag is compromised in any way during shipping, our 100% guarantee means we'll make it right

While you can grow directly in the bag, the best way to grow with bulk substrate is to to use a monotub.

A general rule is 1 colonized grain bag for every 2–3 substrate bags. Higher spawn ratios often speed up colonization and reduce the risk of contamination.

Grain bags are for colonizing mycelium, while sterile substrates (like Boomr Bag, CVG, or Wood-Lovr) are for fruiting mushrooms. You’ll inoculate the grain bag first, then mix the fully colonized grain with your chosen substrate to begin fruiting.

Cluster of brown-capped mushrooms with long, light-colored stems against a white background.

Lab-Crafted. Grower-Approved.

Get the most out of your grow with our premium sterilized substrates—formulated, hydrated, and sterilized to deliver consistent, high-yield results. Each batch is crafted from organic ingredients and sterilized in a commercial-grade autoclave for contam-free performance. Whether you’re spawning to bulk for the first time or fine-tuning advanced grows, our substrates provide the perfect foundation for strong, healthy mycelial growth.

The right mix for every grow

Our substrates start with premium organic ingredients—nutrient-rich, finely milled, and perfectly balanced for ideal texture, aeration, and moisture. Each blend is designed by mycologists to support vigorous mycelial growth and consistent, high-yield harvests. Built on quality ingredients and precise formulation, they’re the foundation every successful grow begins with.

Reviews

  • 5 stars: 122 (93%)
  • 4 stars: 5 (4%)
  • 3 stars: 1 (1%)
  • 2 stars: 0 (0%)
  • 1 star: 3 (2%)
L
Leslie Boehm
AIO bags

Just inoculated 7 days ago. I’ll keep you posted on the progress

Leslie Boehm review photo

Thanks for sharing, Leslie! Our team is here to help if you need anything.

J
Jason

Looks great!!! Inoculated, and already growing well! Hope to have it mixed into substrate soon.

D
Dustin

In the world of mycology, there are many places to buy products; however, no one is better than North Spore! Their customer service services second to none

J
John

Thank you for your help and your products are awesome thank you so much

W
William

Arrived quickly and in good condition. Ready to see what happens. Looks like so high quality grain

t
trey

Colonizes fast

B
Braden
Great value

The 8 pack is an excellent value.

Thanks, Braden! We truly appreciate your support.

J
Jay
Colonized perfectly

Perfect mix to colonize everytime. Thank you .

J
Jessica

Great second time ordering

Happy to hear you had a great experience, Jessica! We're glad everything is working for you so far. Please reach out if we can ever help with anything.

B
Bradley

Exacly what I ordered.

Thanks, Bradley! We couldn’t do it without customers like you. Please reach out if you ever need help with anything.

T
Travis Calovich
The Best

You won’t find much better!

Thanks for taking the time to leave a review, Travis! We couldn't do it without customers like you.

D
David

Great

J
Jack Mitchell
Great products

Always fast delivery

Thanks, Jack! We really appreciate the kind review!

J
John stenner
My grain bags

I am really happy with the grain bags all 8 of them colonized very well they look amazing thank you north spore....

Thanks, John! We love to read reviews like this! It makes what we do all the more worth it.

B
Braden

Really nice thought they were dry at first but just the way millet acts very nice no contam

D
DM

Always a great product 👌 Thank 🙏 you very much.

Thanks for the support, Darren! We couldn’t do it without customers like you. The team is here if you ever need anything.

L
Lori Gagnon

Easy to use and a pretty good price from what ive seen

Thanks for the great review, Lori! We really appreciate your support.

C
Craig W. Beebe
It is grain!

It is grain. It was sterilized. And it's a full 8-pack. Plus, the local Chickadees love that it is organic, as they've become increasingly health conscious.

K
KENDRA KIMBALL
GRAIN BAGS

a few of the bags didn't seem to take but overall-good

Thanks for the honest feedback, Kendra. There can sometimes be a little trial and error, but our customer service team is always here to help if you ever need anything!

J
Jason Keene
Good product

Great bags for mushrooms I love working with them. They work great every time.

S
Scott Schoettle

Great product. Have never had an issue using these. Keep up the great work North Spore.

J
Jason Elder
Outstanding!

I've purchased about 20 bags so far and not one issue. No contaminations, colonized fast, fully recommended!

J
Jim Ferguson
Perfection

As always no problems ever.

We really appreciate the kind review, Jim. We couldn’t do it without customers like you.

T
Taylor Ebinger
Great grain!

Wonderful experience. Immediately took off. My liquid culture loved it.

Thanks for sharing, Taylor. We’re so glad everything is working out for you.

K
Koty

Fantastic product

T
Tiffany

A few of the bags revealed themselves to be contaminated. (I provided them with photographic proof) When I reported it to customer service I was promised store credit for the amount that were contaminated. Hollow promises. (See update) The lack of follow through then ghosting when I followed up is why they are getting 2*

Update: After a prompt response from NorthSpore regarding the issue stated above they were patient enough to walk me through and resend the link for store credit issued to me upon my first report of contaminated grains. I wil continue to be a customer of theirs and am changing my rating to 5* to reflect my current satisfaction as well as previous encounters with exceptional equipment, supplies, and service.

J
Jason Keene
Good

Great

Thanks, Jason!

S
Shawn
Quality products

Quality and clean high success rate

Thanks for sharing, Shawn! If you need help with anything, please reach out.

A
ALEXANDER KINSMEN
Value is great

I value is unbelievable only down side is I don’t think I have the set yet to work thru them all in time!

We really appreciate the kind review, Alexander! We're so glad you are enjoying everything so far.

L
Larz Grenier
Working well!

I inoculated several bags of these and some are colonizing, and some have been sent to produce fruit. Pleased with these bags so far!

So great to hear you are enjoying the products so far, Larz. Don't hesitate to reach out if you ever need anything!

D
Dez Blake
Grain

Arrived quickly and looks just like the picture. I have not had any issues. I will buy again and again and again!

Thank you so much for the continued support, Dez! We so appreciate customers like you!