November 1, 2008 — Botanists developed a spray that, when misted over a plant, will help it endure temperatures 2.2 to 9.4 degrees Fahrenheit colder than it would without the spray, depending upon the species. The spray, called Freeze-Pruf, reduces the freezing point of water inside the tissues of the plant by means of a mixture that combines five ingredients in a water-based spray formula. One spray works for four to six weeks, lowering the temperature at which damage first becomes noticeable as well as the temperature that would normally kill the plant.
Every year, Americans spend more than $38 billion on their lawns and gardens. No matter what you're growing, a sudden frost or freeze can spell serious trouble. Soon, science could come to the rescue with antifreeze for plants.
After 21 years in the nursery business, Margaret Brown knows cold can kill.
"We keep [our] fern houses on about 28 so they can take down a little below freezing," Brown said. Greenhouses keep Brown in business through the winter. For customers who spend hundreds -- even thousands -- on shrubs and flowers, the threat of a freeze is a serious issue.
"The phone rings constantly," Brown said. "I feel like a weatherman in the fall, because everybody wants to know what the weather's going to do."
"At minus 6.6 or minus 6.3 centigrade, plant tissues freeze solid, and we have to deal with that solidity, that freezing," said David Francko, Ph.D., a botanist at the University of Alabama in Tuscaloosa, Ala. Dr. Francko developed a solution that works like antifreeze for plants. It lowers the plants' freezing temperatures and enhances the plants' natural mechanisms to resist freeze damage.
"The ability to reduce the freezing point of water that's inside the tissues of that plant and also, once that water freezes, to allow that plant to survive freezing temperatures [helps]," Dr. Francko said. "It can be frozen solid and still be viable."
A freezing chamber put his freeze-proof solution to the test. Untreated, plant after plant couldn't make it below 30 degrees. Plants sprayed with the antifreeze solution survived the freeze with vital structures still intact. "It's like moving your whole home landscape about 200 miles farther south," Dr. Francko said. "That's about the effect that you get, anywhere from three to 10 degrees more cold tolerance."
As temperatures fall, a dose of antifreeze could buy gardeners and growers a little more time and a little more green. Dr. Green expects the product to be on the market for home and agricultural use by sometime this winter.
WHAT IS FREEZE PRUF? Freeze-Pruf combines five ingredients into a liquid spray to protect against cold damage in plants. The ingredients have a synergistic effect that exceeds the sum of what they would do individually. The ingredients include an antifreeze-like substance that is present in animals, another that helps to lower the freezing point of plant cells by dehydrating them, one that strengthens cell walls, another that helps the solution penetrate leaves, and one to resist washing away by rain and snow. The protection lasts about 4-6 weeks, and the best times to use it are the late fall and early spring.
WHAT IS FROST, AND HOW DOES IT FORM? Tiny frozen water droplets in the air make frost. When water changes to ice (or to steam, when heated) this is a process known as a "phase transition." When water reaches freezing temperature, it will turn into ice. Different materials freeze at different temperatures, but water at sea level will freeze at 32 degrees Fahrenheit. Humidity measures how much vapor is present in the air at any given time. Clear, calm fall nights, when the air mass is especially humid, are the best conditions for frost to form.
Frost is the frozen version of dew, and, like snow, it results from the presence of too much water vapor in already-saturated air. It is a very thin deposit of tiny ice crystals. Frost forms when water vapor in the air condenses directly into ice, instead of condensing first into a liquid, then into ice. Condensation typically occurs when the temperature drops sufficiently for the air to become saturated with water vapor. The excess vapor condenses onto surfaces colder than the air. If the surface temperature is above 32 degrees Fahrenheit, dew will form; if it is below 32 degrees Fahrenheit, frost will form.Frost forms on the inside surface of windowpanes when the air inside has lower humidity than the air outside. If it didn't, the water vapor would first condense into small drops before freezing into clear ice