Spider Farmer 48" x 20.75" Seedling Heat Mat & Controller SetDescription Your seeds will only germinate if they are provided the right environment. Seeds need to be warmer than room temperature (75 80 degrees, to be exact) to sprout, and so you will see a much higher germination rate with a heat mat. Spider Farmer's Seedling Heat Mat warms the root area of seedling 50 77 degrees F above the ambient air temperature, significantly improving the germination process and the success rate of seedlings and cuttings.