This weekend is wall o water setup time. Walls O water (WOW) are extremely valuable devices for helping us have some of the plants in our vegetable garden be harvested earlier than normal; sometimes three weeks earlier.
When a WOW is set over a plant such as a broccoli or Swiss chard, the nighttime temperatures inside the WOW can be up to 8° higher than the air temperature and the plant gets no frost. What is perhaps more important is that after a WOW sits on the top of the soil for about a week the soil temperature inside the WOW will be 5 to 10° warmer than the soil in the rest of the garden. Soil temperature it is really the key to having plants grow quickly in cold weather.
Filling the WOW with water is a tricky business unless you know how to do it. The secret is to put the empty WOW over a 5 gallon plastic can that serves to support the device as you are filling it with water. First you fill a few cells around the device and then you can fill the rest. When all the cells are filled you can pick up the WOW along with the empty bucket and place it in the garden where you want it. A nozzle that can easily be turned on and off is a boon.
I like to set up the WOW at least a week before I expect to place my plants. If the seedling is small then you can squeeze out half the water so that the teepee that is formed is closed at the top. As the ceiling grows taller you can then fill with cells back up to the top leaving a ventilation hole at the top.
You cannot overheat a plant in a W0W as long as the ventilation hole is at the top. Usually you will leave the wall the WOW in place on tell any fear of frost is gone; by two or three weeks.
This year I am using my WOW for a cabbage, two coal Robby, the one roll my tomato, and some summer squash.
WOW should be available in most independent garden centers and are certainly available on the web. If you take care of them and they will last for five or six years. As you can see in the photo they are simply a plastic cylinder design to hold water in cells around the circumference.