Stage 1 of the process
Prepare the substrate
The substrate is the food. Straw only needs pasteurizing in hot water or a cold lime bath; hardwood sawdust with bran or soy hulls must be sterilized at 15 psi. Either way the mix should hold about 60 to 65 percent water.
- Straw
- hot water 1 to 2 hours, or a cold lime bath overnight
- Sawdust block, 5 lb
- about 2.5 hours at 15 psi
Two recipes cover almost every home grow. Straw, chopped and pasteurized, suits oysters and needs no special equipment: a hot water bath at about 150 to 180 F for one to two hours, or an overnight soak in cold water with hydrated lime. How to pasteurize straw compares the methods.
Lion's mane, king oyster, chestnut and shiitake want hardwood sawdust with a supplement: bran, or soy hulls in the half and half blend known as masters mix. The extra nutrition feeds molds as readily as mushrooms, so these bags are sterilized in a pressure cooker at 15 psi, about two and a half hours for a 5 lb block, then left to cool for eight hours or more.
Moisture decides the rest. The target is about 60 percent water for sawdust and a little more for straw: squeeze a handful and only a drop or two should come out. The substrate calculator turns a species, a recipe and a number of bags into dry weights, water and spawn, and the substrate chart shows which species grows on what.
Ready to move on when: The substrate has cooled to room temperature, and a squeezed handful releases only a drop or two of water.
Common mistakes at this stage
- Adding bran or soy hulls and then only pasteurizing: supplemented mixes need full sterilization.
- Using garden lime instead of hydrated lime for a cold lime bath.
- Adding spawn while the substrate is still warm.