Gardening Heating Cable
A gardening heating cable provides bottom heat for your seedlings. It is used to speed up the germination process and to produce vegetables ready for transplanting. This electric cable has a built in thermostat set at 25.6 degrees Celsius and can be used indoors in your kitchen or greenhouse or outdoors in a cold frame or tunnel.
I start my earliest tomato transplants in my living room in February and then larger amounts of other veggies in my plastic tunnel. I place my heating cable in a tray like piece made with plywood. I evenly space the cable on the tray, then bury the cable with and 1/2 inch of sand. I raise it off the ground by placing it on sawhorses or cement blocks.
The following vegetable seeds need heat in order to germinate.
There is a newer product called a seedling warmer. This is a plastic mat that has a heating wire embedded in it. The thermostat is outside the mat so the heat given off by the mat is related to the temperature of the surrounding area. If the room is cool, the mat is 5-11 degrees Celsius warmer.
The seedling warmer has some benefits - it is definitely cleaner and easier to work with especially if you are only planting one tray of seedlings.
I personally still like using the heating cable better as the temperature is the same all the time. The seedling warmer cools and warms as the surrounding area does. The heating cable will heat up to six or more trays at one time, therefore it is much cheaper overall to use.