Seeley Swan Pathfinder -

Q: What are walls of water?

A: They are 18-inch plastic cylinders which act like miniature greenhouses. The wall forms a circle of water-filled tubes. Walls of water can be purchased at a hardware or garden supply store or online. With reasonable care they last for many years.

Walls of water let you plant tomatoes, for instance, four weeks early-not longer than that, because the plant would grow out the top. Inside the wall, temperatures stay above freezing, even when outside temperatures are in the teens, and even when the water in the wall freezes.

The hardest thing about using walls of w...