Second and Third Flushes Fail
Growing conditionsLow urgency
The first flush is fine, but later flushes are small or never come.
Likely causes
- Anaerobic pockets in the core of a deep substrate mass
- Too little nutrition left, or the rest window was missed
- Competitors established during the first flush
- Poor management of the growing room
- Insufficient spawn rate
What to do
Rehydrate and rest the block or bed and re-initiate with a temperature drop, water and fresh air. For next time, use a shallower substrate or better aeration, a higher spawn rate and a richer mix, and stop after the second or third flush if yields no longer pay.
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Sources
- Growing Gourmet and Medicinal Mushrooms (Paul Stamets, 3rd ed., Ten Speed Press), chapter 25 'Cultivation problems and their solutions: a trouble-shooting guide' (Ten Speed Press). Second and third crops that fail to produce substantially or at all are attributed to anaerobic contamination in the core of the substrate mass (increase aeration or decrease the depth of substrate), growing-room mismanagement, a bad strain or an insufficient spawning rate; on blocks that produce a first flush but no later flushes the guide lists inadequate substrate nutrition, competitors and a missed 'window of opportunity' for which the remedy is to re-initiate; the author usually stops shiitake blocks after four or five crops and oysters after two or three.
Last updated: 2026-10-19