Work out mushroom spawn requirement instantly with clear inputs, formula shown and shareable results.
Spawn is added at 1.5-3% of wet substrate weight for oyster mushrooms and 0.5-1% for button mushroom compost. Higher rates colonise faster and reduce contamination risk but cost more, so the rate is a trade-off between spawn cost and the risk of losing a batch.
Spawn requirement
Spawn (kg) = substrate weight x spawn rate %; bags = substrate / substrate per bag
Up to a point. Above about 4% the extra spawn generates heat that can kill the mycelium in the bag centre, and the cost is no longer repaid.
Use within 2-4 weeks of production, stored at 2-4 C. Old spawn has reduced vigour and colonises slowly, which is when competitors like Trichoderma take hold.