It’s been chilly and frosty.
This the most frost I have seen in the corralito, where our highest-chill fruit trees grow, in five winters. (Well, that first winter, the corralito had not yet been built, nor any trees planted.) A lot of people who want to grow deciduous fruits assume you need to have frost. You don’t; in fact, the prime temperature range for the accumulation of needed chilling hours is about 38â€“45, Fahrenheit, and obviously frost occurs at lower temperatures. And when the air temperature is at freezing, the buds’ receptivity to accumulating chill probably freezes, too, until it starts to warm up. Still, when the morning starts off this cold–the photo was taken around 7:30 a.m., when it was 31 degrees–the chilly air is likely to stick around, especially if you can give the trees some shade and if you are in a canyon or valley that tends to trap the cold air. Only by about 10:00 a.m. did the temperature rise above 45, and the high in the winter-shaded part of the corralito (structured so as to “cheat” on the chill) barely reached 60.
Down at the bottom of the canyon, near the neighbor’s vineyard and by the horse track beyond, it was really frosted. This view is taken from the veranda of the house, about 75-100 feet above the elevation of the corralito and about 200 feet above the canyon floor. The canyon floor itself is about 240 feet above sea level, while those twin peaks across the canyon rise to about 1,040. The topography helps channel chilly air and keep it from draining away too fast on a windless morning.
Fortunately, however, there was almost no frost up at the higher parts of Ladera Frutal, where the bananas are planted, about 170 feet above the corralito (525 or so above sea level).
This photo was also taken shortly after 7:30 a.m., but unlike the shaded corralito, this part of the finca was already bathed in glorious early morning sunshine. The very steepness of these canyon walls and the varying sun angles are what give us the luxury of such microclimates.
Nonetheless, even farther up the slope than this location–up at 550 or so above sea level–the low was 33. That’s the smallest difference from top to bottom of the slope that I have seen on any morning when the lowest part dropped to freezing. Usually, when it is this cold, the same clear, dry, and windless conditions that give us the frost help keep the upper reaches of the finca anywhere from five to fourteen (yes, 14!) degrees warmer than the lower. Although there was no frost up there on the higher ground, those subtropicals that I planted back in October could be in danger from this cold snap.