National widespread “winter heat waves” present problems for growers
While “I” am not in any way an expert on horticulture and don’t really have a “green” thumb, I have learned a few things over the past 8-years in this Desert Wonderland.
We desert dwellers have experienced a drought not seen in a half-century and years of hot summers and often cold winters… until 2011 and now into 2012. Now we experience mild winters with short belts of freezing cold only to find the days much warmer than normal — bringing on a Spring that has sprung far too early.
Grapes, figs, flowering plants, roses, shrubs and others that grace our little plot in the desert all seem to be leafing out way too soon. And, indeed they are. Soon the buds of flowers will emerge. Therein lies the problem.
The “winter” has not suddenly changed its calendar. Even though our official calendar indicates that March is when “spring” starts, springtime still harbors bouts of freezing episodes. In our night times from about 1 to 4 or 5 in the morning, FREEZING temps will unpredictably occur. Usually from about 3 to 5 in the morning. A couple hours of freeze is sufficient to severely damage or even terminate the life of some susceptible plants where the more hardy may squeak through.
There are two ways to “help” prevent the loss of our plants. 1) cover them up to help stave off the freezing temperatures, and, 2) Wash off the frost before the sun rises.
Covering can be a massive chore for larger plants like trees, large bushes and shrubs. Lots of tarps, gunnysacks and similar coverings would be needed. Or, wind machines to keep the air circulating, or heating devices such as the old fashioned but effective “smudge pots” found in many fruit orchards. Since method “1″ may not be very practical for the average homeowner, there is method “2″ to take into consideration.
Wash off the “frost” before the sun rises:
Not “all” freezes produce “frost”. Hard freezes are usually around 28°F and freezes around 32°F are a bit more “mild” yet water in a bird-bath is likely to be frozen.
When new leaves, buds and even bursting flowers experience as little as an hour of freezing temperatures, it will generally happen around an hour or two before the sun rises, and as the sun actually starts to break the horizon, the ambient temperatures will actually drop slightly…. on the order of a degree to perhaps three degrees below what it was moments before.
The frost on the foliage is real although you may not actually see it, it is there. The light of the rising sun has the insidious ability to poke its rays through the invisible frost coating on the buds, the tender new leaves and flower petals. The frost acts much like a magnifying glass being used to start a small camp fire. The foliage is subsequently “sun-burned” as the sun’s rays penetrate the frosty coating. Buds won’t open to flower, new sprigs freeze only to die in a few days, new and tender leaves with burnt edges curl… some may survive, some may not.
Here’s a known method of thwarting continued freeze. Wash off the freezy frosty coating. How?
You’ll have to get up much earlier in the morning. If you had set out a shallow pan with water in it, you can simply observe whether or not the water froze during the night. Of course, the pan should be “out there” in the open away from the house or other building — perhaps next to a favorite tree or shrub you hope will survive. A solid crust of ice in the dish, oh, say, a quarter of an inch thick, will suggest that at least for an hour your plants were subjected to freezing temps. The leaves, buds, flowers and new sprigs will have acquired a thin frosty layer that may not be evident to you even when “feeling” with your fingers. But it’s there none-the-less.
As proof, I offer this: Note that strawberry farms, and others, even fruit orchard operators will nearly always set water sprinklers and sprays over their crops, set up with timers to spray plain water over the crops BEFORE the sun rises — but not AFTER. While very small crop establishments can be more easily managed, very large establishments rely on wind machines, smudge-pots, or sprayed water to cover larger areas. While these methods of warding off the problem is not 100% perfect, and some damage may occur, the majority of crops should survive even during 2 to 4 hours of freezing temps.
You must realize that the water coming out of the garden hose, or industrial sized spray equipment, is considerably WARMER than you think. The air temp could be below freezing but the water comes from far away, in underground pipes which has not frozen. If it was frozen, your water would not “run”. Another thing, you don’t need to FLOOD the foliage, just a continuous “mist” spray for a few minutes is all that’s needed.
On the night before, take close note the hour the sun is scheduled to rise. About an hour or an hour-and-a-half before the sun rises, liberally spray your plants, shrubs, bushes, flowers even the trees with a garden hose. Wet them down. This action will wash off the magnifying effects of the frosty coating on the leaves, buds, flowers and thin new sprigs, which will protect them from “sun-burn”, which can cause serious damage to the plant or even ultimate death.
Listen to your local weather forcasts:
Freeze Warning – Widespread temperatures at or below 32°F (0°C) during the growing season. A freeze may occur with or without frost. A hard freeze occurs with temperatures below 28°F (−2°C).
Frost Advisory – Widespread frost during the growing season. Frost generally occurs with fair skies and light winds.
Wind & Frost – If the temp is predicted to be 32° AND the winds at 10 mph or greater, rest assured your plants will be subjected to below freezing temps. It’s the “wind-chill” factor.
It is not uncommon to see citrus groves with ice hang off the fruit and branches when the grower applied a water spray. That “spray” will continue for perhaps an hour or more AFTER the sun has risen. The continuous spray helps in preventing the “sun-burn” effect. Once the sun is “up” and perhaps an hour later one can turn off the spray and the plants will have suffered the “least” damage.