Introducing substrate to colonised grain, often called the spawn-to-bulk stage, is one of the most critical steps in home mushroom cultivation. Wait until your grain is fully white and consolidated, give it an extra week to strengthen, then mix it into pasteurised or sterilised bulk substrate at a ratio of 2:1 or 3:1 (bulk substrate to spawn). Ensure your substrate is at field capacity before mixing, work in a clean environment, and incubate at 21–24°C until the block is fully colonis … read more