Growing Oyster Mushrooms on Scrap Cardboard

This is an experimental mushroom grow. The idea was to see just how sloppy and haphazard I could be and still be successful making food from waste. Oyster mushrooms are a good choice for this as the mycelium is fast-growing and aggressive and tends to beat out mold in a race to colonize the substrate. Oysters are also delicious and easy to preserve. You could also use newspaper, cotton, straw, or other similar plant matter to grow these. In fact using several kinds may be more effective. Inks today are usually soy based and not much health concern.

The plan to sanitize the cardboard is just to boil it. I’m not going to bother with pressure cooking it or even a proper pasteurization. Just fill with water, cover, bring to a boil, and let it cool.

Two pressure cookers were filled. Add water and a handful of garden gypsum for nutrients.

I covered the pots to boil and let them cool overnight. The next day I wrung the wet cardboard out over the sink until it dripped just a little bit- that should hit just the right moisture level. Then put a layer in a cleaned out milk crate, and a handful of rye spawn is sprinkled on top. I made the spawn from rye grain and a liquid culture syringe- that’s another process. Spawn can also be purchased ready-made online.

Layer the spawn and cardboard like lasagna. The cardboard layers were about an inch thick and then a handful of spawn sprinkled on top.

The crate took both pressure cookers full of cardboard.

Stick the crate in a garbage bag and clamp it shut.

Check on the crate every couple days or so. At this point it’s nearly ready to go into the fruiting chamber. Once it’s completely covered in white mycelium, I’ll give it another few days to consolidate, then take it out of the bag and introduce fruiting conditions- that means high humidity and lots of fresh air.

The fruiting chamber has ventilation fans and lighting on a timer and a humidifier connected to a humidity controller. That allows me to dial the climate in pretty well. You could also just cover the crate with a clear plastic bag, and fan it out several times a day and mist the inside with a spray bottle. My setup is just a little more “set and forget”.

The crate is covered in pins (baby mushrooms). I didn’t realize it at the time but it’s too humid in here.

First fruits! They’re really big.

The first harvest. They’re so pretty. With this first flush there were a lot of aborts, I think it was due to both too much humidity and inadequate fresh air. I turned up the fans and down the humidifier. The next flush will be more productive.