Sterilize Master's Mix Substrate Bag — 3 lbs — Hardwood & Soy Hull — For Wood-Loving Mushrooms

3 lbs of sterilized Master's Mix substrate in a professional filtered bag, ready to use with your colonized grain spawn.

Master's Mix is the gold standard for wood-loving gourmet mushrooms. It's a 50/50 blend of hardwood sawdust and soy hull pellets — the sawdust provides the carbon structure that wood-loving species need, and the soy hulls deliver protein and nitrogen for faster colonization and bigger yields. This is the same formulation used by commercial gourmet mushroom farms.

What's inside: 3 lbs hydrated, sterilized Master's Mix (hardwood sawdust + soy hull pellets), supplemented with gypsum

Best for: Oyster, lion's mane, shiitake, reishi, maitake, pioppino, and other wood-loving gourmet species. Pairs with our 3 lb Rye Grain Spawn or Drippy Corn Spawn bags.

How to use: Mix your fully colonized grain spawn into this substrate at a 1:1 ratio. Pack into a grow bag, monotub, or bucket. Colonize in darkness at 70-75°F until fully white, then initiate fruiting conditions for your specific species.

Sterilized — not pasteurized. Pressure cooked at 15 PSI for 90 minutes in a professional filtered bag. The supplemented soy hulls make sterilization mandatory since pasteurization won't fully protect this nutrient-rich mix. Sealed and sterile until you open it. Shelf life approximately 60 days stored at room temperature.