Organic Sterilized Grain Bag with Injection Port

$22.99

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.

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Boomr Bag

Boomr Bag ($28.99)

Perfect for dung-loving mushrooms

CVG

CVG ($22.99)

WoodLovr

WoodLovr ($28.99)

Best for Oyster, Lion's Mane, Shiitake

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In Stock. Ships in 2-5 business days.

USDA Certified Organic

USDA Certified Organic

Trusted by 350K+ Growers

Trusted by 350K+ Growers

Money Back Guarantee

Money Back Guarantee

Successful mushroom cultivation begins with a high-quality, sterile substrate. Our Organic Sterilized Grain Bag with Injection Port offers indoor growers a dependable and convenient foundation for robust mycelial development and spawn production.

Each 3lb bag contains a meticulously prepared blend of organic grains, selected to provide optimal nutrition. This substrate undergoes rigorous sterilization to eliminate contaminants, ensuring a clean and ideal environment for your chosen culture to thrive.

The integrated, self-healing injection port streamlines inoculation. This durable port allows for safe, repeated access without compromising sterility, making transfers efficient for both hobbyists and commercial growers.

Ideal for creating grain spawn or as a foundational component for bulk substrates, this bag supports vigorous growth. It’s a critical first step towards a bountiful mushroom harvest, facilitating successful mycology projects.

Refer to our detailed cultivation guides for proper inoculation techniques and environmental conditions to maximize the potential of your sterilized grain bag.

How to Use

Inoculation

To inoculate the grain bag, simply inject your spore or culture syringe through the port in a sterile location. We always recommend clean hands and latex or nitrile gloves to reduce the introduction of contaminants.

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

We recommend using 2.5-5ccs per 3lb injection port bag. We do not typically recommend using an entire syringe in one bag. Doing so adds excessive moisture which can create over saturation in the bag. This over-saturation can pool and is prone to being anaerobic and the mycelium will have a hard time colonizing.

Colonization

Allow your bag to colonize in a cool location out of direct sunlight. Temperature for incubation shouldn't exceed 75 degrees F or dip below 55 degrees F. After a couple weeks, you should start to see mycelium growing on the grain. 

You'll notice the white mycelium growing outward from the injection point. When it has grown three to four inches you should, without opening the bag, carefully break up the colonized grain and mix it into the uncolonized grain. This will dramatically speed up the colonization process.

When the bag is completely white with mycelium your spawn is ready to use. This may take a couple weeks to a month or more depending on the species and vigor of your culture.

Storage

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

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
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

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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: 859 (92%)
  • 4 stars: 43 (5%)
  • 3 stars: 11 (1%)
  • 2 stars: 4 (0%)
  • 1 star: 14 (2%)
D
David Asplen
Clean product

Grain bags have been reliably clean. Haven’t had any issues with a bag being tainted or dirty. Very happy! Customer service responds quickly as well!

David Asplen review photo

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

S
Sammy Pries jr
Love

This was/is absolutely the best place to get your hands on the best quality supplies for mycology!! North spore is amazing and they are very affordable and very adequate!!! 10/10 every mycologist should have north spore on call!!! They have shown that they are all about their business!! I will never go to another store for anything that involves mycology!! Always be a supporter for north spore

Sammy Pries jr review photo

Wow, thank you so much for the glowing review, Sammy! We appreciate your support.

M
Michael Darkins
So far no issues

Ordered 10 of these bans so far no issues at all. 8 are awaiting to be used. Staggering my grows but they had a deal at the time so I bought to save some money.

Michael Darkins review photo

We're so glad everything is working out, Michael! Please reach out if you ever need anything.

E
Eric Holden
User friendly

Fantastic product, great customer service, wonderful company.

Eric Holden review photo

Thanks so much, Eric! We really appreciate the kind review.

C
Chris
Great product, amazing service.

Nothing but good things to say. Professional and stand by their products! A++

Chris review photo

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

J
James Sullins
Comparison of sterilized grain bags

I inoculated north spore bags and my home made bags with the same spore syringes to compare. In all cases the north spore bags colonized better and faster than my homemade bags.

James Sullins review photo

We really appreciate you taking the time to share your experience, James! Our team is here to help if you ever need anything.

M
Matthew Pinkham
#1 grain bag

The best grain bags in the industry! Always sterile and the equals reliability!!

Matthew Pinkham review photo

Thanks for sharing, Matthew! We really appreciate your support.

A
Anonymous
Colonizing

The bags worked great. I will definitely get my supplies from North Spore.

Anonymous review photo

Thanks for sharing, William! We really appreciate your support.

D
Desirae Reddick
Great!

Love this grain bag. I'm super new to growing and thus made it super easy to start a new hobby

Desirae Reddick review photo

Thanks for sharing, Desi! We're so glad you're enjoying the experience.

J
John

Love all my northspore products

J
John

As always, these products from Northport are great. They are the best. Thank you for everything.

S
Steven

Great product as always! Thanks guys

J
John

Product arrived as advertised. Inoculated and ready to go.

K
Kevin

Its a good item, just arrived dry...

We appreciate your honesty and would love to make this right! Somebody from our team is reaching out to you via email now to assist you with the issue.

N
Nick V
Quality service

My experience has been great, excellent customer service and quality products excited to begin my first flush

Thanks for your review, Nick! Please reach out if you ever need anything.

D
Donald

Thd best grain bags I’ve found on the market.

C
Chuck Lensing

Excellent

M
Matthew
They are always top quality!

Anytime I have issues they always help me!

Thank you for your review, Matthew! Our team is here to help if you ever need anything.

C
Carris
Rough Start

I purchased a liquid culture from a very reputable culture supplier that North Spore provides a coupon code for. I reached out to see if the bag could be replaced and the response I received from the representative was underwhelming and accusatory as if I did not take every measure to prevent molding. I bought more than one refull kit and everything was going extremely well for the other bags with the exception of this particular one. I inoculated the bag in a Nocbox then transferred it to another sterile container with other grain bags. For the most part, I like the products but the response from the representative was extremely disappointing.

Thank you for your feedback, and we're sorry your experience left you feeling disappointed. Our troubleshooting questions are only meant to help us understand what happened so we can set you up for success moving forward. If you reply to the questions, we can send a replacement. We truly appreciate you giving our products a try.

B
Brandon

10/10

F
Franklin

Best grain on the market!

Thanks so much, Franklin! We truly appreciate your support.

D
David

is as described

C
Colton Fowler
MOLD!

I bought a lions mane culture, some grain , and a wood loving soil bag from them and everything was going great the mycelium was taking hold and doing what they were supposed to and then I noticed mold started forming in the bag I tried to rescue the colony but the mold was just relentless my theory is that some spores got in the grain bag at there facility as I bought a grow kit from Amazon to compare the results and kept them in the same sterile grow tent which was wiped down with alcohol wipes twice weekly and used sterile disposable gloves and the one from here is the only one that molded disappointing

Sorry to hear about the contamination, Colton! Somebody from our team is reaching out to you via email now to assist you with the issue.

M
Matthew

Fast shipping. Best quality and guaranteed no contamination

Thanks so much, Matthew! We truly appreciate your support.

J
Jason Keene
Awesome

Great stuff love it

S
Steven

Perfect as always ❤️🙏

N
Natasha Melichar
Amazing product

Super quality and well packed, never had an issue with inoculation through the port, super crafty to come up with that!
Fast shipping!

Thanks so much, Natasha! If you need help with anything, please reach out.