How to read yield curves and flush patterns
How to interpret a yield curve across flushes, spot declining productivity, and decide when a batch has finished producing.
How do you read a mushroom yield curve?
A yield curve plots the weight of each flush against flush number. Most species peak in the first or second flush and decline steadily after. When a flush returns less than roughly a quarter of the first flush, the substrate is usually spent and the batch is ready to retire.
The shape you should expect
A typical oyster batch produces its largest flush first, then a smaller second flush, then a smaller third. The decline is normal and reflects the substrate being progressively depleted of available nutrients.
A curve that rises before it falls is unusual and usually worth investigating. It can indicate a batch that was moved to fruiting conditions too early, or a hydration issue that the first flush partially corrected.
Deciding when to retire a batch
The conventional signal is a flush returning roughly a quarter or less of the first flush. Continuing beyond that point tends to produce small, low-quality fruit while occupying space and increasing the chance of contamination.
Retiring a batch is not failure. Archiving it keeps the harvest history for analytics while freeing the growing space, and the archived data is often what makes a later recipe comparison meaningful.
Using the curve to diagnose problems
A first flush that underperforms across several batches usually points to substrate preparation or spawn rate rather than environment, because the environmental conditions that suppress the first flush would generally also have suppressed colonisation.
A strong first flush followed by a collapse to near zero suggests the substrate was never fully hydrated, or that it ran out of accessible nutrition early. Both are visible as a flat tail on the curve, and both are fixable on the next run.
Comparing curves between species
Species differ in both peak height and how quickly they decline. Oysters tend to produce a high, steep curve. Shiitake on supplemented sawdust typically produces a lower first flush and a longer, flatter tail, which is one reason shiitake blocks are often kept in production far longer.
Because the curve shape is species-specific, comparisons are only meaningful within a species. Comparing an oyster curve to a shiitake curve tells you about the species, not about your technique.
Terms used in this guide
- Spawn
- Spawn is mushroom mycelium growing on a carrier material, most often sterilised grain, used to inoculate a larger substrate.
- Substrate
- Substrate is the material mushroom mycelium digests and grows through, such as straw, coco coir, hardwood sawdust or supplemented pellets.
- Flush
- A flush is one distinct wave of mushroom fruiting from a single batch, harvested together before the substrate rests and produces the next wave.
- Contamination
- Contamination is the presence of an unwanted organism competing with or damaging the cultivated mycelium, such as trichoderma, bacteria, cobweb or yeast.
- Hydration
- Hydration is the amount of water in a substrate, usually expressed as a percentage of the dry ingredient weight.
- Spawn rate
- Spawn rate is the proportion of spawn to substrate in a batch, typically expressed as a percentage of the total wet substrate weight.
Put this into practice
Mushroom.casa Grow Log records stage timings, flush weights and contamination events as you go, and calculates biological efficiency from the numbers you enter. Free for three active batches.