Golden Oyster Colonized Grain Spawn Bag 5 LB
Golden Oyster Colonized Grain Spawn Bag 5 LB is backordered and will ship as soon as it is back in stock.
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Golden Oyster Colonized Grain Spawn Bag 5 LB
Description
Description
Fully colonized Golden Oyster (Pleurotus citrinopileatus) grain spawn, 5 LB, grown on our millet-based grain blend in a filtered Unicorn 3T bag. Built on premium first-generation genetics and produced fresh at our Illinois lab — fully colonized before it ships and ready to break up and inoculate the moment it arrives. Golden Oyster fruits in vivid sunshine-yellow clusters with a delicate, nutty cashew aroma, and colonizes fast and prolifically. Its color makes it a standout at farmers markets and on restaurant plates alike.
We don't stockpile spawn on a shelf for months. Bags are produced on a rolling schedule and held fully colonized, then shipped fresh.
Premium Genetics, Sourced Worldwide
Strong genetics are the difference between a reliable commercial run and a disappointing one — so we built our library from the best sources we could find. Our Golden Oyster spawn starts with our own in-house master culture collection at Myco Labs, refined over years of isolation work, and is expanded through a partnership with one of the largest commercial culture suppliers in Canada, along with select strains sourced from the UK and Asia. Every culture is held as first-generation commercial genetics and selected for vigorous, clean colonization and true-to-type fruiting. This is the genetic foundation serious cultivators build a farm on.
What You'll Receive
- 5 LB of fully colonized grain spawn — premium first-gen Golden Oyster (bags are filled generously and typically weigh in above 5 LB)
- Millet-based grain blend — primarily white and red millet with a small amount of milo; the fine grain gives plenty of inoculation points for fast, even colonization
- Unicorn 10T bag with a 0.22-micron filter patch and self-healing injection port
- 3-mil construction, sterilized in a 3-hour autoclave cycle
- Lab-inspected for contamination and produced fresh at Myco Labs (Illinois, USA)
How to Use Your Grain Spawn
These bags are made to be broken up and mixed directly into sterilized bulk substrate. The most popular method is Master's Mix block production:
- Mix into Master's Mix — break up the colonized grain and combine it with our 5 LB Sterilized Master's Mix. One 5 LB bag inoculates 12–13 Master's Mix bags. Step-by-step walkthrough here: How to Use Grain Spawn with Master's Mix Substrate.
- Expand to more grain — use a portion to inoculate additional sterilized grain (a grain-to-grain transfer) and multiply your spawn before spawning to bulk
- Spawn a monotub or bulk bed — mix into any properly prepared pasteurized or sterilized bulk substrate
For grain-to-grain transfers or any open work, do it in front of a laminar flow hood or clean-room setup. A few minutes under HEPA-filtered air keeps contamination out and dramatically improves your success rate — especially when you're expanding spawn rather than going straight to a sealed Master's Mix bag.
Golden Oyster Growing Characteristics
| Latin name | Pleurotus citrinopileatus |
| Mycelium appearance | White, fast, fluffy growth |
| Spawn-to-substrate ratio | ~1 part spawn to 3 parts substrate (one 5 LB bag → 12–13 Master's Mix bags) |
| Preferred substrate | Master's Mix, hardwood sawdust + bran, straw |
| Fruiting temperature | 65–80°F (warm-loving) |
| Difficulty | Beginner-friendly |
| Use category | Gourmet |
Grain Spawn Specifications
| Net weight | 5 LB advertised (typically fills to ~5.5 LB) |
| Grain | Primarily white and red millet with a small amount of milo |
| Bag | Unicorn 10T, 3-mil, 0.22-micron filter patch |
| Injection port | Self-healing |
| Sterilization | 3-hour autoclave cycle |
| Sterility | Produced under HEPA-filtered laminar flow |
| Shelf life | 90 days best / 120 days refrigerated |
Sterility & Quality Standards
Every bag is produced and inspected at Myco Labs under HEPA-filtered laminar flow, then incubated in a dedicated clean room until fully colonized. Each bag is visually inspected for contamination before it's approved for shipment. If it doesn't look right, it doesn't ship.
Shipping & Handling
Spawn ships in padded packaging. In summer months (May–September) or to hot-climate destinations, we include a cold pack at no additional cost. Use your spawn promptly for best results; an unopened bag stays at peak viability for about 90 days at room temperature, or up to 120 days refrigerated at 35–40°F. Refrigerate if you're not using it right away.
Recommended Companion Products
- Sterilized Master's Mix (5 LB) — the intended pairing; one spawn bag inoculates 12–13
- Laminar Flow Hoods & Clean Room Equipment — for contamination-free grain transfers
- Liquid Culture Syringes — same genetics, ready-to-inject format
- Uninoculated Spawn Bags — to colonize your own grain from culture
Frequently Asked Questions
Is this ready to use, or do I need to colonize it?
It's fully colonized and ready to go. Break it up and mix it directly into sterilized Master's Mix or your bulk substrate of choice — no inoculation, sterilization, or colonization wait on your end.
How many Master's Mix blocks will one 5 LB bag inoculate?
One 5 LB bag inoculates 12–13 of our 5 LB Sterilized Master's Mix bags at our recommended ratio, turning a single spawn bag into a full block run.
Do I need a flow hood to use this?
Not for the simplest workflow — breaking the spawn into a freshly opened Master's Mix bag in a clean, still space works for many growers. But for grain-to-grain transfers or any extended open work, a laminar flow hood or clean-room setup with HEPA-filtered air significantly lowers contamination risk. We carry both in our flow hood and clean room collection.
Where do your genetics come from?
Our cultures come from our own in-house master collection at Myco Labs, plus a partnership with one of the largest commercial culture suppliers in Canada and select strains sourced from the UK and Asia. Everything is maintained as first-generation commercial genetics and selected for vigor and true-to-type fruiting.
How fresh is it, and how long will it stay viable?
Every bag is made fresh at our Illinois lab — never stockpiled for months. An unopened bag stays at peak viability for about 90 days at room temperature, or up to 120 days refrigerated. Refrigerate if you're not using it right away.
Can I use this in a monotub instead of Master's Mix blocks?
Yes. While these are built for breaking up into sterilized Master's Mix, the colonized grain can be mixed into any properly prepared bulk substrate, including a monotub.
What if my bag arrives contaminated or damaged?
We guarantee every bag ships fully colonized and contamination-free. If you receive a contaminated or damaged bag, contact us within 5 days of delivery with a photo and we'll replace it free of charge.
Let customers speak for us
I was getting alot of contam with northspore boomr bag strait garbage company. Contamination central at northspore almost everything contams. I tried a couple other companies then tried this blackcow. Its black gold Texas T the biggest dummy in the world will get massive flushes with this. The grain bags are awesome too and sterilized right. I went 14/14 on the grain bags. Midwest know what they are doing and even the packaging is next lvl everything double bagged. I only buy from midwest it's worth every cent
It's been several days since the Ecosphere arrived and I set it up, and I'm still amazed at all I got for the price: heater, fan, humidifier, two plug-in timers, two foil trays, and, of course, the five-tier tent with shelves and the plastic cover. Oh, and the LED light strip and the round air filters. It's everything I need right now, and I've started the growing process. It's a crazy good deal for the price. I'm new to mushroom growing, and I'm thrilled that I bought this setup as a start. Just plain wonderful.
Fast and easy colonization! These grain jars showed growth after just 10 days. My previous efforts with the all-in-one bags are taking MUCH longer but also working. Thank you Midwest Grow Kits 🙏
I love the people and the products. The people at MWGK clearly care about the integrity of the community they serve.
The monotub works amazing only had it a couple of weeks and about to have second harvest I used AIO grow bag for first flush and move to tub for second and its great not having to watch 24/7. Thanks Midwest
Four days after mixing grain, Select substrate, and the Midwest horse manure booster - the results speak for themselves.
It has everything you need for a fast, large flush success with fewer moving parts than a standard monotub. It is a surprisingly versatile option for more advanced students. Pic is 5 grain jar at 8 days. GT LM This is where I shop, now.
Rich, perfectly field-wet, sterile and it is perfect for those many varieties that won’t thrive quite as well in Bulk Substrate and Casing Mix, which I’ve seen as best for psilocybes/cyanescens. I’m using it for the first time with Lions Mane and King Trumpets. So far so good, 7 days and primordial and pins are starting to flourish. It drains better and is lighter than MGK’s Bulk Casing and Substrate. Great product.
Love the heater and how even and exact it heats. I set mine to 76 degrees and my room fluctuates from 64-75 and it holds solid at 75 degrees. I used a probe thermometer to double check the substrate level temp and its exactly 1 degree less than the heater setting. Another tip, I only needed to use the round monotub thermometer to check my humidity levels every so often. I would leave a filter disk on that hole instead of the thermometer. The only time it came in handy was after my first flush when humidity started to drop. I was able to use that gauge and check whether I needed to mist. Overall great kit and worth the money!
Ive bought mutiple jars before i came up with my own recipe, every jar produced healthy cultures, even if ones damaged in shipping they replace immediately, highly recommend
Very small chance that you get a contaminate you already had it and you’re either culture spores etc. their stuff is 100% sterile every time 100% of the time everything is viable never had a problem been shopping with them for sometime
It’s very good product and I highly recommend it to everyone.👏👏👏
I love my magnetic stir plate it works great for Liquid culture jars.
My bag had a slow start, but excellent finish. Oak Ridge.
Great product for my cannabis best deal around arrived fast thank you Midwest grow kits definitely will be purchasing again
