Gro Quick Electric Soil Heating/Warming Cable-ea 12 Ft Built-In thermostat automatically activates cable when soil temperatures are below 74 degrees This soil warming heat cable will help speed germination and seedling growth. Great to use when starting seeds and allows for early planting. Gentle warm heat. A 12 Foot Soil Heating Cable will allow you to heat approximately 3 Sq. Ft. area. Made in the USA.