Know when to plant. At Territorial, we believe proper soil temperature is a critical element of a gardener's success. Almost every culture block, at the beginning of each seed category, includes soil temperature specifications. Our Soil Thermometer is constructed of durable stainless steel, and the 6 1/2 inch stem will provide you with an accurate reading every time. The zoned dial displays a range of 30-90°F. Guidelines for seed germination included.