Midwest's Select Bulk Substrate Casing Mix - 5 pounds

Midwest’s Select Bulk Substrate Casing Mix – 5 Pounds

Ready-to-Use • Pasteurized • Balanced pH • Ideal Field Capacity for Monotubs & Bulk Grows

Take the guesswork out of bulk growing with Midwest’s Select Bulk Substrate—our top-selling 5 lb substrate blend trusted by growers nationwide. Fully hydrated, pasteurized, and optimized for strong mycelial growth, this ready-to-use bulk substrate is designed to help support fast colonization, healthy pin sets, and heavy flushes in monotubs, trays, and other bulk grow setups.

Formulated through extensive research and real-world testing, this premium blend is enriched with moisture-holding ingredients, mineral support, and a balanced calcium-enhanced pH profile to create an ideal environment for mycelium to thrive. No mixing, no measuring, and no extra prep—just add fully colonized grain spawn and grow.

Why Growers Choose Our Select Bulk Substrate

• Optimized for Maximum Yield – Developed by expert mycologists to provide the ideal structure, moisture retention, and nutrient balance for aggressive mycelial growth and productive bulk grows.
• Perfect Field Capacity – Each bag is pre-hydrated to the proper moisture level, helping create the conditions mycelium needs for even colonization and strong flush potential.
• Ready to Use – No soaking, no prep, and no guesswork. Every 5 lb bag arrives pasteurized and ready to mix with fully colonized grain spawn right out of the bag.
• Pasteurized for Performance – Our specialized pasteurization process is designed to preserve the substrate’s natural growing value while reducing unwanted contaminants, unlike sterilization methods that can strip away beneficial qualities.
• Balanced pH Support – Our calcium and mineral blend helps create a favorable pH environment for mycelium while making conditions less inviting for contaminants.
• Consistent, Repeatable Results – Uniform texture, dependable moisture content, and carefully selected ingredients help deliver reliable performance from batch to batch.
• Trusted by 50,000+ Growers – With over 100,000 bags sold since 2011, Midwest’s Select Bulk Substrate has earned its reputation as a go-to choice for serious growers across the country.

How to Use It

Using Select Bulk Substrate is simple. Start with fully colonized grain spawn, break it up thoroughly, and mix it evenly into the substrate. Once mixed, place it into your monotub, tray, or bulk grow container and allow it to colonize before introducing fruiting conditions.

This ready-to-use substrate helps support a dense, healthy mycelial network while simplifying your workflow. It is an ideal option for both new growers looking for convenience and experienced cultivators looking for consistency.

For best results, make sure your grain spawn is fully colonized before mixing, then distribute it evenly throughout the substrate for faster, more uniform colonization.

Spawn-to-Substrate Ratios & Usage Chart

One 5 lb bag is an easy, convenient amount for a wide range of bulk grow setups. Use the visual chart below to quickly match your grain spawn amount to the correct amount of substrate for common tub sizes and growing methods.

Quick rule of thumb: many growers prefer a 2:1 or 3:1 substrate-to-grain ratio for fast colonization, strong surface coverage, and consistent flushes.

What’s Inside

Select Bulk Substrate is made with a proven blend of premium ingredients chosen for structure, hydration, and performance in bulk grows:

• Coco coir + vermiculite for water retention, structure, and even moisture distribution
• Hydrated lime, calcium, and pH buffers to help maintain favorable growing conditions
• Gypsum, mineral water, and trace minerals to support vigorous mycelial development
• Balanced moisture content for immediate use with grain spawn

Ideal For

• Monotubs
• Bulk trays and bins
• Colonized grain jars
• Rye berry, millet, and 5-grain spawn
• Beginner and advanced growers alike

Storage & Shelf Life

• Short-term: Store sealed at room temperature in a cool, dry place.
• Long-term: Refrigerate sealed bags for up to 6 months.
• Do not freeze.
• Best practice: Avoid extreme heat, direct sun, or repeated temperature swings that may create condensation inside the bag.

Included Bonus Guide

Your order includes access to our step-by-step Bulk Growing Guide (PDF) to help you confidently go from colonized grain spawn to a productive bulk grow setup.