What is a Mushroom Grow Block?

Grow blocks are a fantastic innovation that has allowed growers to produce mushrooms on a commercial level, and hobbyists to find an easy path to grow mushrooms from their own home. Grow blocks are meant to imitate the natural environment that mushrooms thrive in.

So, what even is a grow block? To put it simply, grow blocks are a combination of substrate, cellulose and nitrogen that serve as food, and spawn, which is small pieces of mycelium. Think of mycelium as the “plant” and mushrooms are its fruit, just like a tree grows apples. Mycelium are the roots, the building block for fruiting mushrooms.

The substrate in our grow blocks consist mainly of sawdust and grain. Each of our grow blocks is made with a unique recipe for the substrate to optimize the speed and yield. If you experiment with creating your own blocks, you can try any form of cellulose as the substrate, including straw, hardwood sawdust, cardboard, and grain.

How are grow blocks made? To start, substrate is mixed and hydrated. For our blocks, hardwood sawdust is combined with water, to make a moist consistency, but note it is not drenched, because you want to avoid the invitation of bacteria growth. The substrate is placed into plastic bags, ranging from 3# to 75#, depending on the farm. Our blocks are commercial size, weighing ten pounds! Next comes steam pasteurization, a crucial step to eliminating contaminants. The pasteurization process takes several hours, followed by a cooling period before you remove them from the steamer.

Grow blocks are then inoculated with grain spawn, small bits of mycelium. The mycelium takes upwards of three weeks to expand and colonize the substrate. Once fully colonized, the block is white with mycelium and ready to fruit.

These plastic bags have a white filter, which allows the mycelium to breathe without direct contamination from its environment.

Home gardeners, curious foodies, and serious farmers all benefit from the high quality grow blocks.