Description

Bulk Sterilised Master's Mix Mushroom Substrate Bags – 25–1000 Unit Packs

Scale up your spawn production with lab-prepped hardwood, soyhulls and gypsum substrate that’s ready to mix with grain spawn. Built for growers who care about consistent colonisation, clean results, and a supply they can actually rely on.

Each Master's Mix substrate bag is prepared in clean room conditions and sterilised in a computer-controlled autoclave, taking the guesswork out of prep so you can focus on growing, not fixing problems.

Choose 2kg or 3kg bags in 25, 50, 100, 250, 500 or 1000 unit packs for commercial consistency and better unit economics.

Need trade support, custom scheduling, or a tailored quote? Contact us and we’ll build a supply plan around your volume.

Wholesale‑Ready Sterilised Master's Mix Blend

Our sterilised Master's Mix substrate is a ready-to-use bulk fruiting substrate designed for high-throughput cultivation and trade resale. Each bag is produced under controlled processes to prioritise sterility, consistency, and supply reliability.

Ideal for

• Commercial farms and scaling growers who rely on consistent cycle times and repeatable results
• High-volume hobby growers who want access to wholesale pricing without complicated sourcing
• Retailers and resellers looking for a reliable, high-performing sterile CVG substrate

Not a Bulk Buyer?

This page is for trade, wholesale, and high‑volume growers ordering 25–1000+ units.

If you’re a hobby grower or want to trial smaller quantities first, use our standard (non‑bulk) listing here.

Key Advantages

• Direct from the source - You get the best price. It's all about direct supply from a top UK mushroom supplier.
• Scale whenever you’re ready - Need 25 now or 1,000+ regularly? We’ve got you covered year-round.
• High water-holding capacity - Master's Mix acts like a moisture reservoir, supporting fuller flushes and reducing the need to over-mist or fight drying.
• Clean, commercial-grade sterility - Each batch is sterilised for 2.5 hours at 121°C in a computer-controlled autoclave at our Kent facility, giving you a contamination-free start.
• Perfectly balanced moisture - Master's Mix is hydrated just right to encourage healthy, vigorous growth without inviting bacteria.
• High-quality filtration - 0.2-micron filter patches let the bags breathe while helping keep contaminants out - so you get more consistent results.

What You Get

• Bulk packs 25–1000 to match your production runs
• Two bag weights: 2kg or 3kg to fit different SOPs
• Optimally hydrated hardwood, soyhulls and gypsum blend for rapid colonisation
• Cleanroom-prepped and ready to inoculate on arrival
• Sterilised in a computer-controlled autoclave (2.5 hrs @ 121°C)
• Lifetime Guarantee (we stand behind every bag)
• Free UK delivery on £50+ orders helps protect margins
• Pay in 3 interest-free instalments available at checkout

Built For

Product Sellers (retailers, resellers, garden centres)

• Building a sterile Master's Mix line with repeatable quality
• Offering case quantities for serious growers
• Improving customer outcomes with a proven Master's Mix blend and guarantee

Growers (commercial & high-volume)

• Routine spawn-to-bulk runs with clean, fully colonised grain spawn
• Grain-to-bulk workflows (monotubs and blocks)
• Faster SOPs: no soaking/cooking/sterilising on your end

Perfect For

• Spawning to bulk in tubs using Master's Mix substrate
• Dialing in consistent surface conditions (hydration + airflow) to support strong, even colonisation and pinning
• Repeatable grow cycles when you want predictable bulk-run timing (varies by culture, spawn ratio, and environment)

What’s Included

• 2kg or 3kg sterilised Master's Mix substrate bag (per unit)
• Lifetime Guarantee coverage

Not included: spore or liquid culture syringe.

How It Works

1. Sanitise your workspace and clean your tub/tray.
2. Break up your fully colonised grain spawn in its bag/jar so it mixes evenly.
3. Mix spawn with Master's Mix substrate in your tub/tray until evenly distributed.
4. Level and lightly compress the surface to create a uniform top layer.
5. Incubate until the bulk is fully colonised.
6. Introduce fruiting conditions once fully colonised (fresh air + surface humidity balance).

Quality Guarantee

At Martian Mushrooms, we don't just sell supplies; we use them.

Every batch is produced with lab-first discipline: Master's Mix substrate is soaked/cooked, hydrated to field capacity, and sterilised in a computer-controlled steam autoclave for 2.5 hours at 121°C.

If something goes wrong, you’re protected by our Lifetime Guarantee - built for growers who can’t afford downtime.

Technical Specifications

Martian Mushrooms vs. Competitors

Don't let substrate prep slow you down. Ensure your supply chain with the UK's most reliable Master's Mix substrate.

Need a custom quote, white labelling, or pallet pricing (100+ units)?

Join our Growth Partner Program.