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How to prevent fungal growth on the sides and bottom of the growkit

Polecane produkty

    When you begin working with a mushroom growkit at home — whether it’s a Golden Teacher growkit, Mazatapec growkit, or any other variety — you may start noticing something unusual as the substrate develops. Instead of forming only on the top surface of the mycelium block, small mushroom primordia (known as pins) begin appearing along the sides and even underneath the substrate where it touches the plastic container.

    These tiny pins are the earliest stage of the mushroom’s growth cycle — the same stage we discussed in our guide on the life cycle of magic mushrooms. In a perfectly balanced environment, pins typically form across the exposed surface of the substrate. However, as the growkit matures, the mycelium naturally shrinks and pulls away from the container walls. This creates narrow gaps that trap humidity, stay shaded, and offer a stable microclimate. Because mushrooms instinctively grow where conditions are most favourable, these “hidden zones” often become more attractive than the open top of the cake.

    Seeing pins on the sides or bottom of a growkit may be surprising at first, but it’s a common observation among researchers and hobbyists who study the behaviour of mycelium in controlled environments. In fact, side pinning is one of the key indicators that the substrate is actively searching for the best possible humidity and light conditions. Understanding why this happens is the first step in preventing more complex growkit issues such as compressed mushrooms, excessive moisture pockets or contamination risks.

    • added: 07-11-2023

    When growing psilocybin mushroom growkits, one of the most common issues beginners encounter are side pins – small mushrooms that begin forming on the edges or underneath the substrate cake. Over time these “pins” can turn into fully developed mushrooms trapped between the substrate and the plastic walls of the container. In this article, we explain what side pins are, why they appear, and how to prevent them using simple and safe handling principles. Understanding this phenomenon is essential for anyone studying growkits for research or educational purposes.

    Although removing side pins can sometimes be necessary, preventing them from forming is always a better long-term strategy. Fortunately, most causes of side pins are predictable and easy to manage once you understand how the microclimate inside a growbag works.

    What are side pins in psilocybin mushroom growkits?

    Side pins may look unusual at first, but they are not an abnormal growth. They are simply mushrooms forming in a location that happens to be more attractive than the top of the substrate. A growkit substrate (also known as a cake) is a block of organic material containing mycelium and vermiculite. As it matures, it naturally pulls away from the container walls, creating a small gap. This gap is dark, humid and protected — the ideal micro-environment for mushroom primordia formation.

    If the conditions around the sides are significantly better than the surface (more humidity, less air movement, lower light exposure), the mycelium will prefer this safe zone and initiate pinning there. This behaviour is completely natural, but it often leads to mushrooms becoming compressed against the walls, which increases the risk of tissue damage, trapped moisture and bacterial contamination.

    Why do mushrooms like Golden Teacher grow on the sides of the growkit?

    Side pins in Golden Teacher growkits and other varieties form primarily because the cake shrinks as it consumes nutrients. The space created along the sides traps humidity exceptionally well — often better than the upper surface. Mushrooms instinctively choose the most favourable conditions for growth, even if that space is extremely narrow.

    Although side pins are biologically normal, the tiny pocket between the substrate and the plastic container is highly humid and poorly ventilated. This combination can encourage bacterial growth or mold development, which may compromise the quality of the substrate during observation or analysis.

    Growkit problem: mushrooms growing on the sides or bottom — what should you do?

    If side pins have already appeared, don’t panic — this is a very common growkit observation. You can still reduce their formation and optimise the conditions so that future flushes develop more evenly on top.

    1. Ensure proper moisture distribution

    Side pinning usually means that the top of the substrate is too dry. The solution is not to oversaturate the cake but to improve humidity around it in a controlled way. Lightly mist the inside walls of the growbag rather than spraying the cake directly. This creates an even, gentle humidity gradient that encourages pins on the surface instead of the sides.

    A correctly hydrated cake maintains a balanced surface environment where mushroom primordia naturally prefer to form. Once the upper microclimate becomes more attractive than the shadowy side gap, side pinning decreases significantly.

    2. Block light access to the sides of the growkit

    Light is another pinning trigger. When light reaches the sides of the growbox, the mycelium interprets it as a signal that “this area is suitable for fruiting.” You can limit this by placing the growkit (in its growbag) inside the cardboard box in which it arrived. This keeps the sides dark while still allowing airflow.

    This method works especially well with the newer water-free versions of Golden Teacher growkits. For other varieties such as Mazatapec or B+, ensure the cardboard is tall enough to accommodate the kit including the water if required (around 2/3 of the total height).

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    The content on the psychodelicroom.pl website is educational, research-based and expresses various opinions that should be approached with caution. We do not encourage the use of substances affecting consciousness. In particular, we advise against cultivating mushrooms from growkits in countries where it is illegal — including Poland — as this may involve criminal liability. Growkits purchased from us are intended strictly for laboratory, research or collection purposes and should be disposed of within 72 hours of receipt.