Our Shiitake mushroom grow kits are 100% Certified Organic blocks of enriched hardwood sawdust that is definitely completely colonized by mycelium from our favourite hardy strain of Shiitake. I'm growing mushrooms from mentioned firm talked about in Europe ( chat below) that came previously from the substrate. The YouTube video https://mondo-grow-kit41841.blue-blogs.com/32639174/details-fiction-and-magic-mushroom-grow-kit-usa