Cold December, Hot January

We are in the midst of a very unusual hot streak. For the seventh straight day here at Ladera Frutal, the high temperature passed 80 degrees (on the quaint Fahrenheit scale). This is quite a contrast with December, which featured seven straight days with a high below 60. I am not sure which 7-day streak would be rarer, but neither could be counted on to occur most winters. To have one such hot and one such “cold” streak in the same winter might just be unprecedented. (The December streak even featured a day when the high was only 49; that’s the only 24-hour period in the six-plus-year history of Ladera Frutal’s weather station to feature a high of less than 50!)

So the weather has been weird. And all this weirdness greatly confuses the fruit trees. There have been a few blooms sporadically on the Earlitreat peach since late December. This is not usually one of our first bloomers–it would usually start in mid-February after a few other peaches–but it always is the first ripener. One year it gave us fruit at the end of April. Maybe this year we’ll have peaches in March!

earlitreat_december.jpg

And I was out picking the sumptuous new crop of Page mandarins and suddenly my nose detected one of the most delightful of all fragrances. Could it be? Yes, there are a few blossoms on the Page! (Citrus usually start blooming after mid-March.)

page_january.jpg

There is still no sign of bud break on the usual first-bloomers: the Mesch Mesch Amrah plumcot, Newcstle apricot, Flavor Delight aprium, or Tropic Snow peach. (There have been blooms on the Anna apple, but that doesn’t count; that crazy no-chill apple always blooms in December.) But with such warm weather, I’ll be surprised if one of these is not beginning to bloom by the end of next week.

Of course a limiting factor in triggering blooms will be whether chilling requirements have been met. In fact, it is precisely to guard against too-early a bloom, with possible later freeze or frost damage, that deciduous fruit trees evolved their chilling requirements. If they have not had their chill needs met, they will hold off at least a little bit longer. But at some point, if the warmth continues, they’ll break dormancy anyway, but may not flower or fruit well.

Despite the warm spell, the chill count is pretty good, thanks to two factors: (1) that extraordinary cool week in December, and (2) the dry air. When the air is dry and there is no cloud cover, the nights can be chilly even when the days get quite hot. And it is with dry and cloudless nights that the full flowering, so to speak, of Ladera Frutal’s microclimates become apparent.

Up here at LF HQ, at one of the highest locations on the finca, the hottest day reached 89. That night it cooled to 56. Down the slope, at the coldest part, where all but the lowest-chill deciduous fruits are planted, the high was a bit lower, at 87. But the following night it got to 45. Yes, a 42-degree difference from high to low, and an 11-degree difference in low temperatures between the two locations! What a difference 100 or so feet of vertical change over 200 or so feet of horizontal can make! And in the protection of the big old grapefruit trees, the hedgerow (where I cheat on chill) stays cooler still: the hottest day was 83, rather than 87 or 89, and it is almost always 1-3 degrees colder at night. At times, even just shortly after sundown, we experience a 9- to 12-degree difference in temperature between the locations. Following Madison’s “scientific farming” principles, we have planted varieties in locations intended to maximize their microclimatic adaptation.

As a result of these microclimate effects and the dryness, the chill count is not too bad. Of course, it is not as good as the December cold seemed to promise, but it’s decent. By estimate it seems to have peaked around 310-320 at LF HQ, although we have been subtracting 15-22 hours a day during the hottest phase of the warm spell and now are probably under 250. By my understanding of chill models (and they are just models, not empirical descriptions) that means anything that needs 300 hours to bloom well would be OK, but anything requiring 400 would now need an additional 150, rather than 80-90 before it would be satisfied. Of course, anticipating that this part of the finca might often get under 300 chill hours, I have planted only low-chill varieties up here. (As well as tender subtropicals here and even higher, though that did not work out so well.)

Down in the corralito, at the lowest part of the finca, the chill count is much more impressive. We probably already had 265- 280 by the end of December, and with the impressive cold air drainage down the slope on these dry and cloudless nights, we have had very few significantly negative days. (In fact, at the coldest hedgerow location, none, unless you consider one night of an estimated -.25 chill hours to be “significantly negative.”) Thus down there the trees that are most exposed (to the air mixing of wind and to daytime sunlight) may have had no less than around 350 hours at their peak, while the more protected ones may have had as much as 375 even now (and counting!).

So as long as the heat wave breaks soon and we get even “normal” temperatures for a change, there remain grounds for optimism about the fruit season to come. The forecast calls for only moderate cooling for the next few days, but then a “pattern shift” by the middle of next week. If we are lucky, maybe the rains will return, too.

2 thoughts on “Cold December, Hot January

  1. 86 today. Nine straight days.

    And the Topic Snow peach shows bud swell, so it will probably be in full bloom before the month is done.

  2. Well, the streak finally broke. After ten straight days over 80, today’s temperature maxed out at a chilly 78 (25.6 Celsius).

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