Shiitake Mushrooms (sawdust grown)
 

Sawdust blocks, also called substrata or "artificial logs", are made of sawdust and cooked grains that are sterilized with pressurized steam. They are inoculated with spawn, incubated for 1-4 months and then soaked in water to stimulate the fruiting process. Urea, minerals, and other substances may be added to increase protein and boost nutritional content. The mushrooms are grown indoors with controlled humidity, temperature, electric light, and air flow. Shiitake mushrooms from sawdust logs may all have the same conical shape, many with bulbous stems with pale color and markings (or no markings). The sawdust block is highly susceptible to disease and competing fungi. Some producers use pesticides to control mites or add species-specific fungicides or other chemicals to control disease. The better producers reduce contamination using good sanitation and quality controls instead of chemical controls.