There are a lot of plants (such as peppers and tomatoes) that grow better in soil that has been warmed (between 70 and 75 degrees Fahrenheit). If you are trying to start these plants from seeds, you may want a heat mat. A heat mat is placed beneath the seed-starting containers, and the heat is absorbed by the soil. The plants that need warm soil grow faster because their environment is tailored just to their needs.

Some warming mats are designed to shut on and off automatically, using a thermostat (like in your house) to ensure that the soil temperature remains consistent. Others have to be manually turned on and off, but you can set the precise soil temperature.

But remember, not ALL seeds need heat to grow. In fact, the majority of sprouted seedlings prefer temperatures in the 50 to 60 degrees Fahrenheit range. Once the seeds have sprouted, it’s usually best to remove the heat mats and let the soil cool down.

An excerpt from “Essential Seed Starting Equipment“, courtesy of  Epic Gardening.