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What Are These Strange Blocks? HInt: Composters and Mushroom Fans Will Love Them

Hello! My name is Mikel (Miks for short) and I work at Desert Pearl Mushrooms. Please help me reduce waste while enriching the soil of Tucson – in our yards, community gardens, and farms.

When the substrate blocks that grow mushrooms are done producing a significant yield, they are thrown out. The blocks are made of organic material (wood, soy, and mycelium), and just like kitchen scraps, it is a shame to send this biomass to the landfill. Instead, they should be integrated into the soil for a plethora of benefits, some of which include:

Soil Amendment!

  • Mycelium breaks down chemicals and neutralizes pollutants, such as oils and plastics
  • Acts like manure to assist in crop production or to cover a freshly seeded lawn
  • If trichoderma is present on the substrate, it will help help nearby root systems by combatting any unwanted fungi

Compost Booster!

  • Mycelium feeds on the cellulose and carbon found in compost, while being a food for many of the helpful organisms in your compost bin
  • The substrate is great at retaining moisture
  • If vermicomposting, worms absolutely love to eat the substrate which gets turned into castings, known to be one of the best fertilizers

Mushroom Growing!

  • Though our farm has no more need for these blocks, the mycelium will continue to produce plenty of mushrooms! Trust me, my yard is covered in several varieties of mushrooms which I harvest and eat. My mom grew pounds just in one planter.
  • Varieties that have done very well outside include Lion’s Mane, King Oyster, Chestnut, and Golden Enoki. Shiitake is also available.

To grow mushrooms:
-The biggest key is to keep the substrate moist, as well as the mushrooms when they start growing. There are a few ways to accomplish this:
-If you have a humidifier and want to grow inside, you can set the block close by.
-Build a makeshift canopy out of something like chopsticks and a grocery bag to help keep moisture in. You can then spray the inside of the bag as well as the substrate
-Use a spray bottle or the spray function on the end of a hose.
-Packing the substrate in a pot or planter will help keep in moisture.
-Provide indirect light, such as a north-facing window or under a tree.
-If growing in the ground, dig a shallow basin for the substrate (limit contact to the ambient air). Place near something that you already water to reduce water usage. Burlap or similar can be placed over the substrate and removed once mushrooms appear.
-Growing in the ground can lead to some dirt on your mushrooms. Cool! This is easily cleaned off with a dry towel. If outside the ground, no cleaning is usually needed.

Are you interested? The CSA will have a number of blocks available during pickup hours this week and hopefully occasionally in the coming months.

Currently, I am only offering blocks as they come out of the grow room.  Eventually, I will offer more beneficial forms including weathered substrate, fertilizer, and biochar that are even more nutrient-rich!
Until then, I need your help in using what is available each week. Contact me at if you are interested or have questions and please spread the word to friends in the community. Grab just one or take the whole truckload. I am not currently charging per block, but donations are greatly appreciated.