Don't panic! Most issues have a logical explanation. Find your symptom below.

Phase 1: Colonization (Jars)

🛑 Symptom: Jars Stalled / Not Growing

Mycelium grew for a while but has stopped spreading before 100%.

Possible Causes & Fixes:

  • Lack of Gas Exchange (GE): The holes in the lid might be too small or covered too tightly.
    Fix: Ensure foil is loose or holes are clear (micropore tape allows air).
  • Contamination (Bacteria): Invisible bacteria can halt mycelium. Look for "wet spots" or creamy grains.
    Fix: If bacterial, the jar is likely done. You can try to birth it early and cut off the uncolonized part, but it's risky.
  • Temperature: Too cold (< 65°F) slows growth. Too hot (> 80°F) promotes bacteria.
    Fix: Aim for 75°F (24°C).
  • Dry Substrate: If the mix was too dry initially.
    Fix: No easy fix. Learn for next time.

🤢 Symptom: Strange Colors (Green, Pink, Black)

You see spots that are definitely not white mycelium.

Diagnosis:

  • Green: Trichoderma (Mold). The enemy.
  • Pink/Red: Lipstick Mold or Bacterial. Dangerous.
  • Black: Pin Mold or Aspergillus.
  • Yellowish liquid: "Mycelium Piss" (Metabolites). This is actually okay! It means the mycelium is fighting bacteria.

Action: If it's Green, Pink, or Black -> DO NOT OPEN INSIDE. Throw the whole jar away or empty it outside and bleach the jar. Do not breathe it in.

Phase 2: Fruiting (SGFC)

🌵 Symptom: Cakes Drying Out / Turning Blue

The cakes look shriveled, or the mycelium is bruising blue heavily.

Possible Causes & Fixes:

  • Low Humidity: SGFC not keeping moisture.
    Fix: Mist more often. Ensure perlite is damp (re-soak perlite if needed). Tape up some holes if airflow is too high.
  • Direct Misting: Spraying directly AT the cakes causes bruising (blue).
    Fix: Mist UPWARDS and let it fall gently like rain.

☁️ Symptom: "Fuzzy Feet"

White cottony growth at the base of the mushroom stems.

Cause: Lack of Fresh Air Exchange (FAE)

CO2 is heavier than air and settles at the bottom. The mushrooms are reaching up for oxygen.

Fix: Fan more frequently or more vigorously. Ensure the bottom holes of your SGFC are not blocked (raise the tub on jars or blocks).

🚫 Symptom: No Pins (Mushrooms) Appearing

Cakes have been in the chamber for 2 weeks with no action.

Checklist:

  • Consolidation: Did you wait 1 week after 100% colonization before birthing?
  • Humidity: Must be >90%.
  • Evaporation: Pins are triggered by evaporation. You need the cycle of Misting -> Evaporation. If you mist too much and it never dries slightly, no pins.
  • Light: Is there ambient light? They need a light cycle (12/12) to know which way is up.

🛑 Symptom: Aborts (Black Caps)

Small mushrooms start growing but then stop, turn black, and rot.

Cause: The mushroom "gave up"

Usually due to a sudden change in conditions (temp drop, humidity drop) or the cake ran out of water/nutrients.

Fix: Pick them immediately (they are potent but can rot). Re-dunk the cake if it feels light/dry.

Phase 1 Extended: Colonisation Problems

⏳ Symptom: No Colonisation After 2+ Weeks

You inoculated your jars but see no visible mycelium growth after two or more weeks at room temperature.

Possible Causes and Fixes:

  • Temperature Too Low: Colonisation slows dramatically below 21°C (70°F) and effectively stalls below 18°C (65°F). Mycelium metabolism is highly temperature-sensitive.
    Fix: Move jars to a warmer location. A seedling heat mat set to approximately 24–26°C (75–79°F) placed under the jars significantly accelerates colonisation. Verify temperature with a thermometer placed inside the grow space, not just in the room — heat mats create a gradient and the mat surface can be significantly warmer than ambient.
  • Inoculation Technique: If the spore syringe needle was only inserted shallowly — depositing inoculum at or near the substrate surface rather than deeper in the jar — the mycelium may be colonising but not yet visible through the glass.
    Fix: For future inoculations, insert the needle at least halfway down into the substrate through the inoculation port. Surface inoculation is slower and more contamination-prone than deep inoculation. Check the sides of the jar with a torch — you may see colonisation beginning that is not visible from the top.
  • Dead Spores or Poor Spore Syringe: If the syringe was stored incorrectly (frozen solid, exposed to light, or used well past its use-by date), spore viability may be too low for successful germination.
    Fix: After three weeks with no visible growth, consider the jar a loss and re-inoculate fresh jars with a new syringe from a reputable source. Store spare syringes in a refrigerator (not freezer) at 2–8°C, away from light.
  • Invisible Bacterial Contamination: Bacterial infections can suppress mycelium growth without producing obvious visible symptoms early on. Affected substrate may look wet, have a slightly off smell, or show faint yellowing — all of which can be subtle in the first two weeks.
    Fix: Open one suspect jar carefully and smell the substrate. Healthy substrate at this stage should smell neutral or faintly mushroomy. A sour, sharp, or foul odour indicates bacterial contamination. Discard and investigate substrate preparation — specifically sterilisation time and moisture level.

Phase 2 Extended: Fruiting Problems

🖤 Symptom: Aborts — Pins Start Then Die

Pins form normally and reach a few millimetres, then stop developing, turn dark grey or black, and become soft and slimy. This is different from mature mushrooms harvested at the right time — aborts are young pins that never developed properly.

Possible Causes and Fixes:

  • CO2 Too High: CO2 is heavier than air and accumulates at low levels in insufficiently fanned chambers. High CO2 inhibits pin development and causes aborts.
    Fix: Fan your SGFC (shotgun fruiting chamber) more frequently — at least twice daily, ideally three to four times. Hold the fan or folded cardboard above the chamber and fan for 30–60 seconds to exchange the air inside.
  • Surface Drying: If the outer surface of the cake dries out between mistings, pins that have just formed will abort rather than develop.
    Fix: Increase misting frequency. The substrate surface should look and feel damp at all times without being wet enough to have standing water. If aborts are occurring primarily on the top of the cake, check that the top surface is not receiving direct airflow from the chamber holes.
  • Temperature Fluctuation: A significant temperature drop — even brief, such as overnight in a cold room — can cause pins to abort.
    Fix: Monitor temperature across the full 24-hour cycle in your grow space, not just during the day. Insulate your chamber or move it to a more thermally stable location. A consistent temperature in the range of 22–25°C (72–77°F) is ideal for fruiting.
  • Early Contamination: Contamination that has established in the substrate can cause pins to abort as the mycelium's resources are diverted to fighting the competing organism.
    Fix: Examine the cake surface carefully. Contamination often appears first in areas where aborts cluster. If you see unusual colouring or patches that do not look like mycelium, the cake should be discarded to prevent spread.

🧱 Symptom: Overlay — Thick Crust Blocking Pins

Instead of pins, the surface of the cake develops a thick, dense white mat or crust — almost leather-like in texture — that covers the substrate entirely. No pins appear beneath or through it. This is called "overlay" or "overlay crust" and is one of the most frustrating fruiting problems.

Cause: Mycelium consolidating instead of fruiting

Overlay occurs when conditions that promote continued mycelium growth persist beyond the point where the mycelium should begin fruiting. It is most commonly caused by humidity that is too consistently high without adequate FAE, or by waiting too long after full colonisation before birthing the cake. When mycelium experiences no environmental stress or transition — no evaporation cycle, no light cue, no temperature shift — it continues growing vegetatively rather than switching to reproductive mode and forming pins.

Treatment:

Scratch the surface of the overlay lightly with a sterilised fork or similar tool to break the crust. This physical disruption exposes fresh substrate beneath and creates stress points that trigger pin initiation. After scratching, dunk the cake for 12–24 hours in cool water to rehydrate and restart the pin-triggering moisture cycle. Ensure your FAE is adequate after returning the cake to the chamber — the evaporation cycle (mist, allow to partially dry, mist again) is what signals to the mycelium that it is time to produce fruiting bodies.

Prevention: birth and move cakes to the fruiting chamber within 1–2 days of reaching 100% visible colonisation. Do not allow fully colonised jars to sit for weeks before birthing — the longer mycelium runs out of colonisation tasks, the more it will consolidate into overlay when conditions are stable.

🟡 Symptom: Yellowing Mycelium

The white mycelium on or in the cake develops yellow, golden, or brownish-yellow colouration. This can range from faint patches to widespread discolouration across the entire cake surface.

Diagnosis: Metabolite Exudate vs. Bacterial Infection

Yellowing has two distinct causes that look similar but require completely different responses. The first is metabolic exudate — sometimes called "mycelium piss" or "metabolites" — which is a normal biological process. Healthy mycelium secretes enzymes and waste products as it digests substrate and prepares to fruit. This typically appears as amber or golden liquid droplets or patches, often occurring after a temperature fluctuation or during consolidation. Metabolite yellowing is not a problem: it indicates an active, healthy mycelium. It tends to appear in specific spots rather than spreading continuously, and there is no foul odour associated with it.

The second cause is bacterial infection. Bacterial contamination can produce yellow or golden-brown discolouration that looks superficially similar to metabolites, but has several distinguishing characteristics: it tends to spread progressively from a focal point, the affected substrate becomes wet and slimy in texture, and most importantly it produces a distinctly foul smell — sour, rancid, or putrid. If you are uncertain, the smell test is definitive: healthy metabolite exudate has at most a faint earthy or mushroomy odour. Bacterial-contaminated substrate smells unmistakably wrong.
Fix: Metabolites — no action needed, continue as normal. Bacterial infection — discard the cake immediately, do not open it inside your grow space, and review your substrate preparation and sterilisation process for the next batch.

🦠 Symptom: Contamination Appearing After Casing or Birthing

Your jars looked clean and fully colonised, but contamination appeared after you cased or birthed them. The timing of contamination appearance provides important diagnostic information about where the problem originated.

Timing Is the Clue:

  • Contamination within 24–48 hours of inoculation: If mould or contamination appears very early — within one to two days of inoculating your jars — the spore syringe itself was likely contaminated. Contaminants introduced at inoculation have a head start over the mycelium and establish quickly.
    Fix: Discard all jars from that inoculation run and obtain a replacement syringe. Check the syringe under strong light against a white background — healthy spore solution should appear clear to light brown with evenly distributed particles. Cloudiness or visible floaters suggest contamination.
  • Contamination appearing only after casing or birthing: If the jars colonised normally and appeared clean throughout, but contamination appeared after you handled and moved them, the original grain or substrate was probably carrying suppressed contamination. A vigorous mycelium can sometimes physically outcompete a small bacterial load during colonisation, keeping it suppressed. When the cake is then birthed and the mycelium is stressed by handling and environmental transition, the suppressed contamination resurfaces.
    Fix: Review sterilisation time and pressure for your substrate preparation. BRF jars sterilised by pressure cooker at 15 PSI for 60–90 minutes should be reliably sterilised. If you are steam-sterilising without pressure, extend sterilisation time significantly (2–3 hours) and investigate whether your setup reaches and maintains 100°C throughout.

💧 Symptom: Wet Rot — Mushy, Discoloured Substrate

Portions of the cake become soft, mushy, and discoloured — often appearing dark brown, grey, or yellowish-green — and may have a distinctly foul or sour odour. The affected areas lose their structural integrity and collapse when touched. This is sometimes called "wet rot" and is among the most unambiguous signs that a cake is unrecoverable.

Cause: Bacterial Infection from Overwatering or Poor Drainage

Wet rot is a bacterial infection most commonly caused by over-misting or water pooling on the substrate surface. Bacteria thrive in waterlogged conditions where gas exchange is limited — the same conditions that mycelium find difficult. A cake surface that remains visibly wet for extended periods between mistings, or a chamber where water pools at the base and keeps the lower portion of the cake saturated, provides ideal conditions for bacterial establishment and spread.

Wet rot is effectively unrecoverable once established. Unlike green mould (Trichoderma), which sometimes remains confined to a limited area, bacterial wet rot tends to spread progressively through the substrate. Attempting to cut out the affected portion and continue fruiting the remainder is rarely successful and risks spreading the contamination further.
Fix: Discard the affected cake in a sealed bag. Clean and sanitise your fruiting chamber. For future batches, adjust your misting technique: always mist the walls of the chamber and fan to allow evaporation rather than misting the cake surface directly. The goal is high ambient humidity (90%+) with the cake surface damp but not visibly wet. If water pools at the bottom of your SGFC, your perlite may be over-saturated — tip out excess water and allow the perlite to drain before returning cakes to the chamber.

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