by Warren Schultz
If I were selling advertising for the local TV or radio station, I think I'd spend this month knocking on the doors of the local bed and bath shops. Think about it. Who are the most interested people in weather reports this time of year? Gardeners. We spend our time listening raptly, waiting for the inevitable frost warning. And once that warning comes what do we do? We festoon our yards with old (or not so old) sheets and blankets. Let's face it... And when time is short and the old blankets are no where to be found, well, the new ones will just have to do. If we have to buy more to replace them, well, hang the expense.
That kind of casual covering will protect crops down to a few degrees below freezing. But there are other ways, including a high tech method I learned back on the farm some thirty years ago. Though this technique practiced by citrus growers in Florida and strawberry growers in California, it hasn't really caught on with home gardeners. Maybe it's just to weird. It amounts to using ice to prevent crops from freezing.
By the time frost threatened on the farm, most of our crops had been harvested and sold. After the bottom dropped out of the tomato market we opened the field to the pick-your-own crowd who picked it clean. Corn was not a big concern, once labor day passed and the kids were back in school, our customers craving for corn dropped precipitously. Melons had run out of juice during the shorter days and weaker light of late summer. But peppers were a different story. They were still growing; still bringing good money on the market. Finishing up that crop could mean the difference between a good year and a bad one. So we did all we could to delay their death by freezing.
When frost threatened we were once again turned out of our beds in the middle of the night, but not to cover plants with bushel baskets or soil, but to set up the irrigation system in the peppers. It must have been a ghostly sight for late night travelers on the road past the farm. A handful of men and boys moving silently, dreamily through the moonlight, carrying balancing thirty-foot lengths of aluminum pipe on their shoulders. (Why didn't we do it earlier? Because we spent all the daylight hours picking all the peppers we could.)
When the irrigation pipe was all hooked up and the temperature dipped below 35 degrees F. we cranked up the pump and set the sprinklers spinning. We ran it all night, stopping only torefuel. In the morning the peppers were covered with a thick coat of ice. But as it thawed the peppers were solid.
How could that be? As a kid the idea that a pepper could be coated with ice without freezing fascinated and puzzled me. So I sought out, presented the question to the next best thing,closest thing we had to Mr. Wizard. His explanation about hear loss and gain didn't fully satisfy me, but it turned out to be pretty darn close to the truth.
The process is actually a good demonstration of the principle of the latent heat of fusion. (Don't call it cold fusion or you'll get the Academy of Sciences excited all over again.) It's pretty simple. As water turns the ice it gives off 144 BTUs of heat per pound. This heat energy is available to theplant to keep its tissue from falling below 31.5 degrees F. And that's warm enough to prevent damage. It works as long as the air temperature doesn't drop below 20 degrees F.
You can try this at home. Of course, you'll need a reliable sprinkler with an even distribution pattern and a high pressure so that the water sprayed is as close to a mist as possible. An impact sprinkler is best. Just start the sprinkler when thetemperature dips below 35 degrees and let it run continuously until well after the sun has risen.
Some cautions: the flow rate of the sprinkler must be slow,to prevent too much water and ice from building up on and breaking the plants. The rate should be between 1/6 and 1/4 inch of water per hour. The sprinkler should be high quality so that it doesn't leak around the head and cause an ice build up that will impair interfere with sprinkler action. The sprinkler head should make at least one revolution per minute to insure that there is a constant film of fresh water over the frozen coating on the plant. The sprinkler must continue to run until the ice on the plant begins to melt rapidly.
I know this will work on peppers. I suspect it will on tomatoes. It's worth a try on other crops. But I wouldn't do it if I had to pay for water, or had a well that was subject to running dry. Still, if you do it properly you're going to use only about 10 gallons of water per 100 square feet per hour. And just think of all the money you'll save on sheets and blankets.
Copyright NGA
Reprinted with permission HouseNet, Inc.
Peppers on ice