Grow problems
Mushroom grow kit not growing? Check these causes
Updated
Most grow kits that do nothing have one of five problems: the block is not fully colonized, the room is too warm or too cold, the air is too dry, there is too little fresh air, or the kit was not opened where it needs to be. Work through the checklist below in order. A healthy kit usually pins within one to two weeks once all five are right.
How long should a kit take before you worry?
Give a kit two weeks from the day you open it before you worry. Most kits arrive fully colonized and pin in one to two weeks. Slow species take longer: Lion's Mane pins in about 5 days in its profile, Maitake in about 10, and Shiitake needs a cold shock first. See how long mushrooms take to grow for every species.
Is the block fully colonized?
A ready block is white all the way through and firm. Brown patches of sawdust mean the mycelium is still working. Keep it closed, warm, and out of direct sun for another week. Yellow or amber drops on the surface are normal and often show up when it is nearly done. A shiitake block should be brown on the outside before it fruits.
Is it too warm or too cold?
The profiles pin at 15 °C (59 °F) to 24 °C (75 °F). Above about 24 °C (75 °F), most species other than Pink Oyster slow down or stall, and warm, still air invites mold. Cold rooms slow everything. Blue Oyster and Enoki like it cool, Pink Oyster and Golden Oyster like it warm.
Is the air too dry?
Pins form on a damp surface. In a heated or air conditioned room the cut face of a kit dries out within hours. Mist the opening two or three times a day, never so much that water pools, or cover the kit with a loose plastic tent with holes. The profiles fruit at 82 to 93% humidity. Dry, cracked, or yellow pins are the sign. See dry or cracked mushroom caps.
Is there enough fresh air?
A kit sealed in a bag, a cupboard, or a closed box builds up carbon dioxide, which tells the block to wait. Pins that do form grow long stems and tiny caps. Give the opening room air several times a day. In its fruiting stage Pearl Oyster runs a fan run of 40 s every 10 min. Commercial oyster growers aim for 4 to 6 fresh air changes an hour (UC ANR) and keep carbon dioxide under 800 ppm (SARE and FungiAlly). Check a chamber with the fresh air planner, and read leggy mushroom stems.
Is there enough light?
Most species need light to know which way to grow. Indirect daylight or room light for about 12 hours a day is enough. A dark closet can stall pins for weeks. Direct sun is too much and dries the block. Enoki and Button / Cremini are the exceptions that fruit with little or no light.
Was the kit opened in the right place?
Pins grow where the block meets air. Most kits want an X or a slit cut in the side of the bag, about 5 cm (2 in) each way. A kit left closed can sit for weeks, or pin inside the plastic. If pins are forming inside the bag, cut it open right at that spot. Some kits need soaking in cold water first. Follow the instructions that came with it.
Is the kit old or contaminated?
Kits keep for a few weeks in the fridge, less on a warm shelf. An old kit shrinks away from the bag and may be slow to wake up. Green, blue, black, or pink patches, a slimy surface, or a sour smell mean contamination. Do not eat from a moldy kit. Read mushroom contamination to tell mold from healthy mycelium.
Why did my kit stop growing after the first harvest?
That is normal. A block needs one to two weeks of rest after a flush to build up for the next one. After the rest, soak it in cold water for a few hours to replace the water the first flush used, drain it, and set it back up in fruiting conditions. Expect a smaller second flush. Most kits give two or three flushes before they run out of food. When a block stops pinning after that, break it up into garden soil or compost.
When should you give up on a kit?
If a fully white kit has had two to three weeks of the right temperature, damp air, fresh air, and light, and a cold soak, with no pins, it is probably spent or the culture is weak. Contact the seller, since many replace kits that never fruit. If it is contaminated, bag it and throw it out away from your other blocks.
Still stuck? See why mushrooms are not pinning for more on fruiting triggers, or find your species in the conditions for every species.
FAQ
Why is my mushroom grow kit not growing?
Usually the block is not fully colonized, the room is too warm or cold, the opening is too dry, there is too little fresh air, or the kit was not cut open where it needs to be.
How long should I wait for a mushroom kit to grow?
About two weeks after opening. Most kits pin in one to two weeks. Slow species such as lion's mane, maitake, and shiitake can take longer.
Why did my mushroom kit stop growing?
After a harvest a block rests for one to two weeks. Soak it in cold water for a few hours after the rest and it usually pins again, with a smaller flush.
Can a mushroom kit grow again?
Yes. Most kits give two or three flushes with a rest and a cold soak between them, each smaller than the last.