There are two main reasons mushrooms stall in the fruiting phase. The first is genetic 🧬. There are literally hundreds of mutation that can occur, or you selected a non fruiting isolation in culture.
Genetics is too broad to get into and there’s usually little that can be done to get the cake fruiting and thriving again, if the cause is genetic.
The other reason is environmental conditions 🏝️ ☀️. Since we see so many home cultivators, we can go a little into what makes a cake stall besides genetics, because I see this a lot.
In general, a stall happens because the mycelium is under physiological stress or has redirected its energy away from fruiting.
The most common causes are:
1.) Hidden contamination (most common), bacterial contamination (often Bacillus, Pseudomonas) is a frequent cause of stalls.
2.) Early-stage molds such as Trichoderma can suppress growth before green spores appear, the mycelium may stop expanding, become dull, or produce excessive metabolites (“myc piss”)
3.) Suboptimal moisture: Too Dry and the mycelium dehydrates and cannot support pin formation.
4.) Too wet: Waterlogged substrate limits oxygen diffusion and favors bacterial growth.
5.) Poor fresh air exchange (high CO₂)
High CO₂ suppresses normal fruiting.
Symptoms include delayed pinning, fuzzy feet, elongated stems, or complete failure to initiate pins are all gas exchange problems and can be corrected in the next flush.
6.) Temperatures below the optimal range slow metabolism significantly. 70° F (21°C).
7.) Insufficient humidity (below 70% RH) Low relative humidity can cause primordia to abort or prevent pins from forming. Surface moisture is often more important than absolute chamber humidity.
8.) Surface conditions:
A dry, matted, or heavily overlaid mycelial surface may not readily produce pins.
Conversely, standing water on the surface can also inhibit pinning.
9.) Poor gas exchange within the substrate
Overly compacted substrates or excessive water content reduce oxygen availability inside the block.
Healthy mycelium requires oxygen throughout the substrate, not just above it.
10.) Nutrient depletion or aging
Older spawn loses vigor. Happens most often with CVG substrates.
11.) Over-colonized spawn can become less capable of producing vigorous flushes. (Overlay or stroma)
12.) Senescence, after many transfers age out. Signs are slower colonization and reduced fruiting.
Some of these are reversible if you catch them in time. Some of these like genetic, and contamination require starting over and nothing can be done to remedy. If you’re getting lots of aborts in the first pin stage then usually your cake is done and the reason for the stall is multifaceted.
Obviously you can alter conditions. It’s much easier to do if you’re growing in a Martha Tek Tent, monotubs are alittle harder to alter conditions but not impossible.
So, those are the reasons we stall in the fruiting phase. Of course, knowing the reason is alot of guesswork. The prognosis depends on many factors but If I had to say the top reasons is moisture and FAE or too heavy of a pin set to be supported by existing moisture and nutrient balance. Too dry or too wet can be corrected. CO2 problems can be corrected.
Go through each of these and assess whether or not it requires intervention. If you’re gonna try and reverse, you need to adjust one thing at a time. Don’t go making a bunch of changes at once to air and moisture and humidity. Just one at a time. If the cake starts growing again you’re good. If you see NO change in 2 weeks, let your cake go and start again. All the conditions that are reversible will do so quickly. After 2 weeks I consider a stall permanent and I retire the cake.
Hope this helps answer questions about your stalled cakes. Let me know if you have any more questions.
Please 🔼 upvote if you find this helpful.
Thx
Trip
