The concept is simple: surround plants with a wall of water that collects sun energy during the day and releases it at night, protecting the plant from cold temperatures. It's like a mini greenhouse with extra insulation.
Wall O'Water advertises that you can plant six to eight weeks early, without fear of freezing. Burpee suggests using Aqui-Shield up to one month early. As efficient a system as it is, I feel more comfortable with the one-month guideline.
You begin by planting your plant normally. Tomatoes prefer a soil temperature of at least 60F degrees. Below 50F degrees and roots won't grow. If your soil hasn't warmed sufficiently, cover the bed with plastic for a few days to help raise the soil temperature.
|Plastic warming the soil|
After the plant is in the ground, cover it with a five-gallon bucket. This is the support you need for the plastic. Don't try to fill the tubes with water without a bucket in place. You'll make a mess, probably break your plant, and waste a lot of effort.
|Covering the plant|
Arrange the plastic season extender around the bucket. It doesn't need to be perfect, just try to space it as evenly as you can. Fill each of the tubes about two-thirds full with water. I recommend using a hand-controlled hose nozzle. You can just let the hose run free while you fill the tubes, but it will create a mess. Control is better.
|Filling the plastic tubes|
With water in each tube, carefully remove the bucket, making sure you don't snag or injure your plant.
|Removing the bucket|
The tubes will collapse at the top, forming a teepee. This is the key to early season protection. The plant is full enclosed by the plastic and water and the temperature inside stays nice and toasty, just what the warm season plants like.
|The finished teepee|
In a few weeks you can expect the plant to start peaking through the top of the teepee. Average day and night temperatures will be warmer and you won't need full enclosure of the plant. At this point, fill each of the tubes to the top with water. The extra water will expand the plastic and create a cylinder with the top open. The plant will be able to grow through. You may need to add water every few days to keep them filled.
You still need to water the plant too, though it shouldn't be as often as other unprotected plants. The plastic teepee will help keep the moisture levels of air and soil higher. Don't assume the plant is doing okay with this protection. Check the condition of the plant and of the soil moisture regularly.
|Watering through the top|
After all danger of frost is past, at least two or three weeks after the last frost date, it's time to remove the season extender. This can be a little tricky because you have a great deal of water in the tubes and the plant is almost certainly growing out the top. I recommend laying a mulch like straw around the base of the plastic and squeezing the tubes to try and push out as much water as you can. This helps avoid a muddy mess. As carefully as you can, without breaking or injuring the plant, slide the plastic up and over the plant.
With the plastic system off and out of the way, drain the water out and lay it in a place where it can dry out completely. You'll be able to reuse it for years, but you don't want to put it in storage if there is still water in it; mold will definitely develop. If you are impatient and it's not drying quick enough, you can try using a blow dryer on the cool setting to blow air into the tubes.
These season extenders definitely work. In conjunction with a mini-greenhouse hoop system like I showed in my blog, "Extending Your Growing Season with Mini Greenhouses", I think you could plant six to eight weeks early as long as the soil temperature is warm enough when you first plant. Especially in very cold regions with short growing seasons, these extenders will allow you to grow plants you might not be able to grow otherwise.
At a cost of between four and five dollars each, they're affordable and considering that they can be reused for years, you're investing an extra dollar or so on each plant. The extended season that you gain should more than repay that investment with additional produce.