Six symptoms that account for most of our support mail, each with the one variable to change rather than five.
Long stems, tiny caps
This is carbon dioxide. The mushroom is reaching for air exchange, and it will do it in a sealed tent at any temperature on earth. Change one thing: fresh air. Open the lid fully twice a day, or point a small fan at the wall of the chamber so the air turns over without blowing on the fruit.
Do not fix it by lowering the humidity – pins will dry and abort instead, and you will have solved one symptom by causing a worse one. For king oyster and lion's mane, expect this on the first grow and get used to reading the shape as feedback.
Pins appear, then shrivel and stop
Abortion is nearly always water moving the wrong way: either the pins dried out because the humidity dropped while they were expanding, or the block is waterlogged and the surface has soured.
Raise humidity above 85 % and stop misting the pins directly – mist the walls and the air. If there is free water pooling in the bottom of the box, tip it out, stand the block on a rack or a bottle cap, and leave the lid cracked for a day.
The third cause people miss
A cold draught across the tent. A north-facing windowsill in February will abort a whole shelf while the middle of the room reads a perfect 19 °C. Measure at the block, not at the wall.
Yellow or wet-looking surfaces
On lion's mane, a yellow drip on the spines means either too much water sitting on the fruit or the mushroom releasing spores because it is over-mature. Dry the surface, mist the air only, and harvest.
Elsewhere, a slimy sheen with a sour smell is bacterial blotch. Remove the affected fruit, cut the humidity and surface water back, and improve the air exchange. A block with a sour smell throughout is finished: compost it rather than trying to rescue it.
Green, black or pink patches in the substrate
That is contamination, and there is no technique that saves an open bag of it. Do not open it in your kitchen: bag it, take it outside, and dispose of it. Mould spores released in a small room will simply find your next block.
Then work backwards honestly. Green mould usually means one of three things: work done in moving air, substrate that was pasteurised when it needed sterilising, or a bag left open while you went to find something. Two of the three are solved by a still air box, which is why we list one under beginner essentials.
Nothing is happening, and the block is white
A fully colonised block that will not pin is usually not warm enough, not cool enough, or not getting the trigger it wants. Species are picky in different directions: oysters and lion's mane want a couple of degrees of swing between day and night; shiitake wants a cold rest of five to seven days; king oyster wants both that and much more air.
Give it a soak to rehydrate, rest it five days dry, then return it to the temperature the listing names and stop touching it for a week. Most 'dead' blocks produce within eleven days of somebody leaving them alone.
A fine white powder on the plastic, then on everything
That is wet or dry spore fall from an over-mature crop, and if you let a flush go that far in an unventilated room it settles on the shelves, the fan and the next block. Harvest earlier – this is the same advice as for yellowing, and it is the reason we tell you to pick before the caps flatten.
If you are sensitive to mould or you are growing in a bedroom, do not run a sporing crop there. It is not a mushroom problem, it is an air problem, and it is entirely avoidable by picking on time.
Medical note: if you are immunocompromised, talk to a clinician before keeping fruiting blocks indoors. This is a genuine question, not a disclaimer, and we would rather you asked.
The short version
- Point a fan at the chamber wall, twice daily air changes. For long stems
- Raise humidity above 85%, mist air not fruit, drain pooling water. For aborted pins
- Bag and dispose outside; do not open it indoors. For green mould
- Soak 12–24h, rest 5 dry days, then leave it alone a week. For a silent block
Kit list for this guide
GROWING SUPPLYUltrasonic Humidifier, 4 L, with Hose Port$54.00
GROWING SUPPLYDigital Thermo-Hygrometer with Remote Probe$18.00GROWING SUPPLYFruiting Tent with Shelves and Humidity Tray$72.00Written by the MycoGrow fruiting room. No claim here guarantees a harvest: a grow is a living thing in a room you control, and the room is the variable.
Leave a Reply