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5-Grain or Rye? Choosing the Right Spawn Bag
Both bags use the same sterilization process, the same Unicorn 10T bag spec, the same 3-mil construction, and the same self-healing injection port. The only difference is the grain inside. Here is how to pick.
Premium 5-Grain Spawn Bag (Top Seller)
Best for: Most growers. Faster colonization, easier to break apart, ideal for monotub spawning.
A 2-quart bag (2.25 to 2.5 lbs) containing a blend of rye berries, white milo, red milo, white millet, and red millet. The mix of grain sizes creates significantly more surface area than any single grain, which means mycelium colonizes faster. Smaller grains also break apart easily when you shake the bag during incubation, distributing mycelium throughout and speeding up colonization further.
This is what most experienced monotub growers run. Faster, easier to mix into bulk substrate, and produces consistent results.
Original Rye Berry Spawn Bag (Classic)
Best for: Growers who prefer pure rye, working with a workflow built around single-grain rye, or species that perform particularly well on rye.
A 2-quart bag (2.25 to 2.5 lbs) containing 100 percent rye berries. Rye has been the standard mushroom grain for decades for good reason: dense, nutritious, and supports strong, vigorous colonization. It takes slightly longer to colonize than the 5-grain blend (rye berries are larger and have less total surface area), but many experienced growers prefer the consistency and tradition of pure rye.
How to use a spawn bag, start to finish
Both bags use the same workflow. Here is the complete process.
Step 1: Inoculation
- Shake your liquid culture syringe to evenly distribute mycelium.
- Flame-sterilize the needle until red-hot, then let it cool for 10 to 15 seconds.
- Wipe the self-healing injection port on the bag with 70 percent isopropyl alcohol.
- Inject 2 to 4cc of liquid culture through the port. More is not better.
- Cover the port with a piece of micropore tape (optional but recommended for extra contamination protection).
Step 2: Incubation
- Store the bag at 70 to 75 degrees Fahrenheit out of direct light. A closet, cabinet, or dedicated incubator works.
- Check daily for the first signs of growth (small white fuzzy patches near the injection site, typically within 5 to 10 days).
- Once mycelium has covered 30 to 50 percent of the bag, break and shake: gently break up the colonized clumps and shake the bag to distribute the mycelium throughout the uncolonized grain. This speeds up the remaining colonization significantly.
- Full colonization typically completes 14 to 21 days after inoculation. See our spawn bag colonization timeline guide for what to expect at each stage.
Step 3: What a fully colonized bag looks like
You are looking for the entire bag to be uniformly white with mycelium, with no visible grain still showing through. The mycelium should be dense and even, not patchy or spotty. There should be no green, blue, black, pink, or orange patches anywhere in the bag (those colors indicate contamination).
A healthy fully-colonized bag is firm to the touch and the grain inside should feel like one solid block of mycelium-bound grain.
Step 4: Spawning to bulk substrate
- Wipe down your work area with 70 percent isopropyl alcohol.
- Open the bag and break up the colonized grain back into loose pieces.
- Mix into bulk substrate at roughly a 1:3 grain-to-substrate ratio. Recommended amounts by tub size:
- 28Q small tub: Best results with one 32oz grain jar (a spawn bag works too, paired with 4 lbs of bulk substrate)
- 44Q medium tub: One spawn bag (2.25 to 2.5 lbs) plus 7.5 lbs of bulk substrate
- 66Q large tub: Two spawn bags (5 lbs total) plus 10 lbs of bulk substrate
- Transfer the mixed spawn-and-substrate into your monotub and start the fruiting cycle.
Bag specifications
- Bag: Unicorn 10T spawn bag, 3-mil thickness
- Filter: 0.22 micron filter patch for gas exchange and contamination protection
- Port: Self-healing injection port for syringe inoculation
- Sterilization: Pressure-sterilized in our autoclaves for 3 full hours
- Grain weight: 2.25 to 2.5 lbs per bag (2-quart capacity)
- Production: Made fresh daily, in-house at Midwest Grow Kits
- Shelf life: Best within 90 days, up to 120 days refrigerated
Frequently Asked Questions About Spawn Bags
How long does a spawn bag take to colonize?
Typical colonization is 14 to 21 days at room temperature (70 to 75 degrees Fahrenheit) when inoculated with a quality liquid culture syringe. Spore syringes take longer, often 21 to 35 days. Breaking and shaking the bag at 30 to 50 percent colonization speeds up the remaining colonization significantly. For a full timeline breakdown, see our spawn bag colonization guide.
How much liquid culture or spores should I inject?
For a 2-quart spawn bag, inject 2 to 4cc of liquid culture through the self-healing port. For spore syringes, the same 2 to 4cc range works. More is not better. Over-injection wastes culture and can introduce more potential contamination from the syringe itself.
What is the difference between the 5-Grain and the Rye Berry bags?
The 5-Grain bag blends rye berries with milo and millet to increase surface area, which speeds up colonization and makes the bag easier to break up and mix into bulk substrate. The Rye Berry bag is 100 percent rye, the classic single-grain mushroom standard. Both work well. The 5-Grain colonizes faster; rye is preferred by traditionalists and works particularly well with certain species.
Should I break and shake my spawn bag during colonization?
Yes. Once mycelium has covered 30 to 50 percent of the bag, gently break up the colonized clumps and shake the bag to distribute the mycelium throughout the uncolonized grain. This creates many new inoculation points and dramatically speeds up the remaining colonization. Do not shake the bag too early (before significant colonization) or you risk disrupting the initial growth.
What does a contaminated spawn bag look like?
Healthy mycelium is uniformly white and slightly fuzzy. Contamination shows up as colored patches: green (typically Trichoderma mold), black or dark gray (Aspergillus or bacterial), pink or orange (various molds), or wet slimy patches with a foul smell (bacterial contamination). If contamination is small and localized early on, the bag may still colonize successfully. If it spreads or smells bad, bag it up sealed and dispose of it without opening indoors.
Why are your spawn bags sterilized for 3 hours?
Most DIY home sterilization runs 90 minutes or less, which kills active microbes but does not reliably kill endospores (the dormant, heat-resistant forms produced by some contaminant bacteria). Three hours at full pressure in our autoclaves kills endospores too, which is why our bags have a dramatically lower contamination rate than typical home-sterilized grain.
How long do spawn bags last before they need to be used?
Our spawn bags work best when used within 90 days of production. Refrigerated, they can last up to 120 days. We make bags fresh daily and ship the freshest stock first, so the bag you receive will typically be just days old.
What temperature should I store an unused spawn bag at?
If you plan to use the bag within a couple of weeks, room temperature is fine. For longer storage (up to 120 days), refrigerate at 35 to 40 degrees Fahrenheit. Do not freeze. When you are ready to inoculate, bring the bag back to room temperature for at least 24 hours before injecting.
How many spawn bags do I need for a monotub?
It depends on tub size. For a 28Q small monotub, we actually recommend a 32oz grain jar over a full spawn bag for best results (though a spawn bag with 4 lbs of substrate also works). For a 44Q medium monotub, use one spawn bag plus 7.5 lbs of bulk substrate. For a 66Q large monotub, use two spawn bags plus 10 lbs of bulk substrate. These amounts are dialed in for the size of each tub and the optimal grain-to-substrate ratio.
Can I use a spawn bag for grain-to-grain transfers?
Yes. A fully colonized spawn bag can be used to inoculate additional sterile grain bags, dramatically expanding a single culture into multiple grows. Grain-to-grain (G2G) transfers should be done inside a laminar flow hood or still air box since the bag has to be opened. Use a small amount (a few tablespoons of colonized grain) per fresh bag.
Do I need a flow hood to inoculate a spawn bag?
No. The self-healing injection port is designed for sanitary inoculation in a normal room with basic technique: alcohol on the port, flame-sterilized needle, clean hands. A flow hood or still air box reduces contamination risk further and is required for any work that involves opening the bag (such as grain-to-grain transfers), but it is not needed for initial injection.