Frozen Fruit, Anyone?
April 2. I’m up early again this morning, awakened once again by the roar and throb of our neighbors’ wind machines and the question whether to add ours to the chorus. For over a week now it’s been an early-morning routine: either our alarm thermometer goes off or we hear someone else’s machine start up. Usually both. The thermometer tells us that temperatures are heading into the critical range where damage to the tender fruit buds will occur. The neighbors’ wind machine tells us that he thinks there’s enough warm air above and that by mixing it with the cold air trapped near the ground he may be able to stave off some damage. I phone the CSU Extension Service Experiment Station to connect to their reporting thermometers, one at fruit level and one at 40 feet above, and see whether there is a temperature “inversion” — one mile away. My neighbor (one-half mile distant) also has an elevated thermometer. But also has a couple of machines that turn on automatically. Has he made a calculated decision or not?
So the deliberation narrows: how localized is the inversion? How severe is the frost? How steeply is the temperature declining? Is there any cloud blanket? Any wind? How soon will the sun be up? One thing’s for sure — I’m up and not likely to get back to sleep with all those questions and machines stirring around. So far, we haven’t turned on our machine a single time this year. But maybe I’d better call the station again…
Up to last week we were headed into an early spring. Day after day of warm, dry, bluebird days. The fruit trees awakened almost a month ahead of average: buds were swelling and showed hints of pink blossoms. The further advanced the bud development the more vulnerable to frost damage. We monitor the bud stages and correlate to charts depicting temps where 10% bud kill is expected all the way down to 90% bud kill. We set the alarm thermometer accordingly.
Then came the first cold front — roaring in on 50 mph winds and sending the mercury plunging to 13 degrees. We welcomed the snow that followed but worried for the fruit. A succession of fronts, wind-events, snows, and storms has followed. It’s winter again, time to break out the fleeces and boots again. But try telling that to the trees: they can’t go back to sleep. So we engage in early morning deliberations that reduce to weighing whether the cold is due to a cold-air-mass that we can’t do anything about or radiational cooling that we can temper by turning on the big fans. A morning like today where the temp is hovering around 20 degrees (well into the critical zone) is actually a relief from recent mornings when it just keeps sliding into the teens.
So, what are our prospects for the fruit season? After the first two cold nights we clipped a few representative peach branches and brought them inside to dissect the buds in search of the tell-tale brown of freeze damage. Before we accomplished this, though, we had another very cold night, and our earlier results were obsolete. Now those buds are swelling to beautiful pink blossoms in a vase in our living room. We’re not without prospects to report, however. Our friends at the Experiment Station have been diligently dissecting bud samples and their reports are far more encouraging than our fears had been. We still have at least a month of exposure to potential frost events, so prognostications remain premature but we’re again optimistic for a bountiful harvest.
Just to be sure, I phone again for the temps at the Experiment Station… No change… I can continue to peck at my keyboard, and sip morning tea by the warm fire, and listen to my neighbor’s wind machine and wonder what he knows that I don’t…