Midwest's Select Bulk Substrate Casing Mix - 5 pounds
Midwest's Select Bulk Substrate Casing Mix - 5 pounds is backordered and will ship as soon as it is back in stock.
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Description
Description
Midwest's Select Bulk Substrate is a pasteurized, pre-hydrated CVG mushroom substrate (coco coir, vermiculite and gypsum with lime and trace minerals), ready to mix with colonized grain spawn straight out of the 5 lb bag.
It's our top-selling bulk substrate, built for monotubs, trays and bins. Every bag arrives at field capacity with a balanced pH, so there's no soaking, measuring or pasteurizing on your end. Just spawn to bulk and grow.
Pasteurized, pre-hydrated CVG substrate that's ready to mix with colonized grain spawn. No soaking, measuring or pasteurizing.
- 5 lbsPer bag
- CVGCoir, vermiculite, gypsum
- PasteurizedReady to use
- 2:1–3:1Substrate to grain
- 6 monthsRefrigerated, sealed
Why growers pick Select Bulk Substrate
We pasteurize every batch ourselves. It knocks back competing microbes while keeping the substrate's natural biology, which is what you want in a bulk grow.
Squeeze a handful and you'll get a drop or two, never a stream. No water to add and no guessing at moisture.
Hydrated lime and gypsum buffer the pH and Azomite adds trace minerals. Same texture, moisture and pH in every bag, so results repeat tub to tub.
Spawn to bulk in 4 steps
All you need is fully colonized grain spawn and a clean monotub or tray.
1Break up the spawn
Start with grain spawn that's completely white. Massage the bag until the grain separates into loose kernels.
2Open the substrate
Pour it into a clean monotub or tray and crumble any clumps so it's loose and even.
3Mix it together
Combine spawn and substrate evenly at 2:1 to 3:1 substrate to grain, then level and lightly press the surface.
4Colonize, then fruit
Cover and leave it undisturbed until the surface is white, usually 2–3 weeks, then introduce fruiting conditions.
Bulk Growing Guide included. Our step-by-step bulk monotub guide walks you from colonized grain spawn to a fruiting tub.
How much do I need?
One 5 lb bag
One 5 lb bag fills a Small 28Q tub on its own. For bigger tubs, use the amounts below.
- Small 28Q: about 4 lbs, plus 1 spawn bag or one 32 oz jar
- Medium 44Q: 7.5 lbs (our 7.5 lb bag), plus 1 spawn bag
- Large 66Q: 10 lbs (2 bags), plus 2 spawn bags
Keep bags sealed in a cool, dry place, or refrigerate sealed bags for up to 6 months.
Don't freeze, and avoid heat and big temperature swings that cause condensation in the bag.
Specifications
| Specification | Detail |
|---|---|
| Weight | 5 lbs per bag |
| Base | Coco coir, vermiculite and gypsum (CVG) |
| Additives | Hydrated lime, mineral water, Azomite trace minerals |
| Treatment | Pasteurized |
| Moisture | Pre-hydrated to field capacity; no water needed |
| Spawn ratio | 2:1 to 3:1 substrate to grain |
| Works with | Rye, millet, 5-grain and other colonized grain spawn |
| Storage | Sealed, cool and dry; refrigerate up to 6 months; do not freeze |
Pick the right size
Select Bulk Substrate 5 lbThis product
Select Bulk Substrate 7.5 lbFills a 44Q tub
Select Bulk Substrate 6-PackSix 5 lb bags
Premium 5-Grain Spawn BagsSterilized grain spawn
| 5 lb Bag | 7.5 lb Bag | 6-Pack | 5-Grain Bags | |
|---|---|---|---|---|
| Use it for | One Small 28Q tub | One Medium 44Q tub | Several tubs or a Large 66Q | Your grain spawn |
| Quantity | 5 lbs | 7.5 lbs | 30 lbs (6 × 5 lb) | 2-quart spawn bags |
| Step | Spawn to bulk | Spawn to bulk | Spawn to bulk | Inoculate and colonize first |
| Pairs with | 1 spawn bag | 1 spawn bag | 2 spawn bags per 66Q | Any Select bulk bag |
Trusted since 2011More than 100,000 bags sold to over 50,000 growers. Pair it with our Premium 5-Grain or Original Rye spawn bags.
FAQ
What is in Select Bulk Substrate?
A CVG base (coco coir, vermiculite and gypsum) with hydrated lime to buffer pH, mineral water and Azomite trace minerals. It comes pre-hydrated and pasteurized.
Do I need to add water?
No. Every bag is hydrated to field capacity before it ships. Open it, break up any clumps and mix in your colonized grain spawn.
What should it look like when I open the bag?
Dark brown, moist and crumbly, with light flecks of vermiculite. If you squeeze a handful, you should get a drop or two of water, not a stream. Some clumping from shipping is normal; just break it up.
Is it pasteurized or sterilized?
Pasteurized. That reduces competing microbes while keeping the substrate's natural biology, which is the standard approach for bulk substrate. Your grain spawn is what gets sterilized.
How much do I need for my monotub?
About 4 lbs for a Small 28Q, 7.5 lbs for a Medium 44Q (our 7.5 lb bag) and 10 lbs (2 bags) for a Large 66Q.
What grain spawn can I use?
Any fully colonized grain spawn: rye, millet, 5-grain bags or grain jars. Aim for 2:1 to 3:1 substrate to grain.
Can I use it as a casing layer?
Yes. Mix it through as your bulk substrate, or spread a thin layer over colonized substrate as a casing.
How should I store it?
Keep bags sealed in a cool, dry place short-term, or refrigerate sealed bags for up to 6 months. Do not freeze.
