Spawning is the mushroom culture equivalent of planting seeds for a field crop. However, mushrooms are “planted” using fungal mycelia rather than seeds. Fungal mycelium propagated vegetatively is known as spawn (Latin expandere= to spread out). Spawn making requires special “clean room” laboratory facilities to propagate mycelia, so the mushroom mycelia do not get mixed with the mycelia of other fungi. Spawn making starts by sterilizing a mixture of cereal grains plus water and chalk; rye, wheat, millet, and other small grains are used. Once the sterilized grain has bits of mycelia added to it, it is incubated to promote its full colonization. Mushroom farmers purchase spawn from commercial laboratories around the U.S. and Europe. The “seed” for a typical room at Mountain Meadow costs about $1,200.00.
At our farm, spawn is thoroughly mixed into the compost using a special hydraulically powered spawning machine. Once the spawn has been mixed throughout the compost, the compost temperature and the relative humidity in the growing room are managed to optimize mycelium growth. The spawn grows out in all directions from a spawn grain. The time needed for spawn to fully colonize the compost depends on the amount of spawn added and its distribution, the compost moisture, temperature, and the nature or quality of the compost. A complete spawn run usually requires 10 to 14 days.