Midwest's Select Bulk Substrate Casing Mix - 7.5 pounds
Midwest's Select Bulk Substrate Casing Mix - 7.5 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 in a 7.5 lb bag is a pasteurized, pre-hydrated CVG mushroom substrate — coco coir, vermiculite and gypsum with lime and trace minerals — sized to fill a Medium 44Q monotub with one spawn bag.
Same blend as our 5 lb bags, in the exact amount a 44-quart tub takes, so there's no leftover half-bag. It arrives at field capacity with a balanced pH: open it, mix in colonized grain spawn and grow.
- 7.5 lbsPer bag
- 44QOne tub per bag
- CVGCoir, vermiculite, gypsum
- 1 bagGrain spawn needed
- 6 monthsRefrigerated, sealed
Why growers pick the 7.5 lb bag
- One bag, one tub – 7.5 lbs is the right amount for a Medium 44Q monotub with one grain spawn bag.
- Ready to use – Pre-hydrated to field capacity and pasteurized. No soaking, mixing or measuring — open the bag and add colonized grain spawn.
- Pasteurized, not sterilized – Pasteurization knocks back competing microbes while keeping the substrate's natural biology, which is what you want in a bulk grow.
- Balanced pH and minerals – Hydrated lime and gypsum buffer the pH, and Azomite trace minerals round out the blend for vigorous mycelial growth.
- Consistent batch to batch – Same texture, moisture and pH in every bag, so your results are repeatable from one tub to the next.
How to use it
- Start with fully colonized spawn. Grain spawn bags or jars should be completely white before you spawn to bulk.
- Break up the spawn. Massage the bag or shake the jar until the grain separates into loose kernels.
- Open the substrate. Crumble any clumps so the substrate is loose and even.
- Mix it in the tub. Combine spawn and substrate evenly in a clean monotub or tray, then level and lightly press the surface.
- Colonize, then fruit. Cover and leave it undisturbed until the surface is colonized, then introduce fruiting conditions.
Breaking up colonized spawn and mixing it into bulk substrate.
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 7.5 lb bag fills a Medium 44Q tub. For other sizes:
| Monotub | Substrate | Grain spawn |
|---|---|---|
| Small 28Q | About 4 lbs | 1 spawn bag or one 32 oz jar |
| Medium 44Q | 7.5 lbs (one bag) | 1 spawn bag |
| Large 66Q | 10 lbs | 2 spawn bags |
Specifications
| Specification | Detail |
|---|---|
| Weight | 7.5 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 |
Storage: Keep bags sealed in a cool, dry place for short-term storage, or refrigerate sealed bags for up to 6 months. Do not freeze, and avoid heat, direct sun and big temperature swings that cause condensation inside the bag.
Growing in a 44Q tub?The 44Q refill kit pairs this amount of substrate with a spawn bag, filters and a liner. Starting from scratch? The Complete 44Q kit includes the tub. Other sizes: 5 lb bag or 30 lb 6-pack.
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.
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.
What size tub does 7.5 lbs fill?
A Medium 44Q monotub, spawned with one grain spawn bag. For a Small 28Q use about 4 lbs; a Large 66Q takes 10 lbs.
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.
