Pacific Northwest Gardening: My new greenhouse!, 1 by

wrote:
These cables are meant to warm soil and have pots put on top of the warmed soil. I have found that sitting the pots directly on top of the mats makes the soil dry out too fast. It works better if there is a cushion of air between the mat and the pots. I use these drying trays, from an old fruit drying unit I got at Goodwill (seems like I find them all the time). They work great because they are about an inch tall and are perforated at the top, allowing the warm air to rise around the pots.