When soil temperatures are ideal, the body of the morel begins to fruit as a tiny knot on an underground network of mycelium, a complex of long, thread-like fungi cells. The knot rapidly enlarges until it becomes a tiny club that pushes its way to the soil surface.
Morels grown under controlled conditions for commercial purposes fruit when the soil reaches a consistent temperature of approximately 53 degrees F. Wild morels also appear under these conditions.
Use a probe-type digital thermometer to take soil temperatures. Take the temperature daily and be consistent. Take it in the same spot, at the same time and at the same depth (preferably 2 to 6 inches).
Many factors can influence the soil temperature, including the amount of leaf litter or debris on the ground, the amount of sunlight, rain and air temperature. When weather conditions cause the soil temperature to increase rapidly, morels will appear suddenly. If soil temperature warms slowly, morels take longer to develop.