Spring can be fickle in northern latitudes, laying waste to entire gardens planted just a little too early. If you're a winter-weary gardener anxious to get things going, take heart. You can start your gardens early using season extenders such as walls of water. A cheap and easy version of this useful device can be made at home with a few materials you probably already have on hand. Your homemade walls of water will absorb heat from the sun during daylight hours and then keep your young plants warm overnight. Although they may last only one season, they are easily constructed from recycled and readily available materials.
Arrange seven clean and empty 2-liter plastic soda bottles on a flat surface, so that one bottle is in the center and the other six are tightly clustered around it.
Tear off a piece of duct tape long enough to stretch all the way around the circle of outer bottles. Attach one end of the tape about midway down the side of one of the outer bottles. Wind the rest of the tape snugly around each outer bottle, and then secure it to the first end of the tape. Don't worry if the tape is uneven, just make sure that the bottoms of the bottles line up together.
Turn the taped bottles over, and carefully pull the center bottle out by its bottom, leaving a ring of outer bottles with a void in the middle.
Place the ring of bottles around a young plant in the garden, and fill the bottles to the top with water using a hose. Do this in the early morning so that the water will be heated all day by the sun.
Add one teaspoon of bleach to each bottle to prevent the growth of algae and screw down each cap securely.