Temperature means, winter months, 2013-18

By popular demand*, here’s a full accounting of our winter temperatures since moving to the current location.

The stats really drive home just what an unusual winter this was, with the colder temperatures very much concentrated towards the latter part. I discussed the consequences of this for the deciduous fruit tree blooms in an earlier “planting“.

February’s mean low was more than four degrees below the five-year mean, and the March high and low were both 3-4 degrees below the five-year means.

December was also colder than normal, in terms of overnight lows although the daytime highs were the warmest experienced in a December thus far. The December cold was not as far below norm as we experienced our first winter here, 2013-14, when an extreme freeze was very costly to some of my citrus and other subtropical trees. Even the Eucs had damage that winter.

* Not really, I must admit.

Apricot blooming, 2018

The ‘Canadian White Blenheim’ apricot has reached full bloom. It has the pinkest flowers of any of the ten or so apricot varieties I’ve ever grown over many years. Strange, given that its fruit has one of the palest flesh tones of any apricot.

Canadian White Blenheim

This variety has fruited for me before, both here and in inland San Diego County. However, we have never had more than a few fruits in any one year, and the modal number of fruits of this variety per year has been zero. That is because it has had blooms that were anything but profuse. It is a pretty clear law of fruit-growing that if you have no blooms, you get no fruit.

In past years, when this variety has bloomed, it has been not only sparse, but also very late relative to the leafing out. That is unusual, in that most stone fruits are at full bloom before leaves really begin to emerge. I always assumed that the culprit was chilling; a stone fruit is unlikely to have a proper bloom if it has not met its winter chilling need during the dormant period. (Dave Wilson Nursery suggests 700 hours chilling needed for this variety.)

There was no question of chill not being met this year. While January was quite warm, both December and February had good long periods of chilly weather and deep cold snaps. In fact, the big fear I had was that an unusually late cold snap would adversely affect fruit trees, many of which typically begin blooming here by mid-February. Indeed, the ‘Flavor Delight’ aprium was in full bloom just when a hard freeze hit. While the tree’s foliage has recovered, there is no sign of any fruit set. The freeze hit it at just the wrong time.

Meanwhile, the ‘Royal’ (‘Blenheim’) apricot has had an odd spring. Normally, it would be blooming in mid/late February. It has a relatively low chilling requirement (from much experience, I’d estimate it at around 350, even though many catalogs and other sources say 400-500). Yet it remained mostly dormant until well into March. And it was not just my own rather old tree; a few trees with ‘Royal’ tags on them, planted on the UC Davis campus a few years ago, did the same. This is very strange.

Perhaps even stranger is that just now my ‘Royal’ is blooming like the ‘Canadian White Blenheim’ normally does–after it has leafed out. It has about a dozen blooms right now, scattered amidst well developed foliage.

Royal apricot

In many years of growing this variety, I have never seen it do this. So, just as one variety that normally blooms sporadically post-leaf-out is instead having a more normal-looking bloom, here an old reliable is exhibiting the staggered behavior of a tree that got insufficient chill.

It has been an odd winter, and even odder bloom season. It is too early to know if the white apricots will set fruit. I express that in the plural, because the ‘Monique’–another even whiter variety that also is hard to get to set in our climate–also had a pretty good bloom this year. The ‘Hunza‘ (a real favorite of mine with luscious complex-tasting flesh and an edible kernel) also is in full bloom right now.

So, while one can’t count one’s fruit this early*, indications are promising for the later-blooming trees. Another law of fruit-growing is that a profuse bloom does not guarantee a good fruit crop, but it certainly makes it more likely.
*Today is the eve of Pesach (Passover). Somewhere in the Talmud it is suggested that Shavuot is the “Yom Kippur of fruit trees”, the day one which they are judged. That is about right, as in roughly fifty days we will have passed through (over?) the most perilous time for developing fruit. What holds that long has a pretty good chance of making it.

Freeze of 2018 update

It got cold. Even colder than forecast. Five out of six nights over the past week saw sub-freezing temperatures. Friday night it was 29F as early as 10:30 p.m. and it was 26 as late as 6:30 a.m. Saturday and not above freezing till about 8:20. That is a lot of cold for the time of year, especially given that this time of year is bloom season for almonds and many stone fruit.

The most sensitive trees I have here are two citrus trees. This is how I covered the ‘Gold Nugget’ mandarin. In addition to this tent, I have a string of lights on the tree (note orange extension cord). I placed a hi-lo thermometer inside. The temperature under the tent never reached freezing, thanks to the heat from the lights and the thick greenhouse-style plastic.

The other one I always protect in freezes is the ‘Wekiwa‘ tangelolo. In addition to this plastic over a frame, inside I have placed not only a string of lights but also a heat lamp (the kind made to keep chicks warm). On that cold Friday-Saturday, the lowest it got in here was 39.

Note the new leaf shoots at the top of the branches. These are what I was most worried about, as this is where flower buds will form soon. This variety may be hardy down to the low 20s (and this tree did survive 20F, albeit with extensive damage, without a heat source in Dec. 2013). But new growth would not take well to repeated freeze exposure.

Blooms of deciduous fruit and nut trees also do not take well to freezes. Many such trees were already breaking dormancy when the cold struck. My ‘Flavor Delight’ aprium was in bloom by about the 15th of the month. All signs were encouraging for good fruit this year, after a year when it did not fruit (due to heavy rain during this time of year in 2017).

Immediately after the freeze, the tree looks like this:

The flowers have all collapsed. They were near the end of their bloom anyway, but this dramatic a collapse likely means major damage. There also are no leaf shoots, as there normally would be as the bloom wraps up. There are a few buds in evidence, and the tree itself likely will be fine. But I certainly would not count on any fruit. Many other stone fruits had buds swelling before the freeze, and those could have been rendered non-viable by cold temperatures.

As I said in the earlier post in anticipation of the freeze, I do not have to count on fruit and nut trees for income. For those that do, this past week has been very rough. Almond growers, whose trees reach peak bloom around this time, are looking at substantial damage. Some will come through OK, others may have total losses. It will be a while before a full damage assessment can be made. If you like almonds, expect to pay more for them this year. California’s Central Valley produces most of the world’s supply. The effects of this freeze will reach far.

Here comes the freeze of 2018

I just can’t believe these local forecasts. For tonight:
“Patchy frost after 4am. Otherwise, mostly clear, with a low around 30. West wind 11 to 21 mph, with gusts as high as 26 mph.”
For tomorrow night:
“Areas of frost after 4am. Otherwise, mostly clear, with a low around 27. Northwest wind 10 to 13 mph.”
Normally here, if it is going to be that cold, there’s no wind at all. This is the most ominous forecast I’ve seen since January, 2007, when we were still in San Diego County. That week, I lost a large percentage of my subtropical fruit trees.
In this climate, I don’t have subtropicals, but I do have citrus. Plus because it is the second half of February, the deciduous trees are either blooming, or have buds ready to open. A freeze could ruin any hope of fruit.
I don’t make a living growing fruit. But spare some thoughts the next few nights for those who do. California looks like it is about to be hit hard by one of its worst freezes in over a decade.

A tale of two curry-leaf trees

When I planted our older, potted, curry leaf tree last summer, I thought where I was putting it would be protected and that the tree would do better in its new ground location than where it had been growing in the pot. Apparently not.

That is it, in a spot protected by taller trees and a fence, with only a few leaves on it in early February. (It is an evergreen, but will drop leaves in response to sharp cold snaps.) Meanwhile, an offspring of the tree, growing next to a different fence where the parent used to be, looks great.

Sometimes plants really surprise me. The potted one looked pretty unhappy its first winter at the location when we had some significant cold snaps. But the offspring has shown no leaf loss this winter, even though we’ve had a couple of periods of temperatures in the high 20s.

Both should be fine–the transplanted one gets less sun this time of year but will get plenty as we get farther into spring and summer. And it shows no major stress, even if it has few leaves at this point. In fact, with another cold snap coming, it may be better off than its offspring on account of being somewhat dormant.

Spring 2018. Or is it winter?

Sometimes in a climate like this one, the seasons kind of mash together. It was an unusually warm January, and some trees are in bloom now. Yet this morning the temperature was 30F and there were ice crystals on the grass.

First blossom one one of our almond trees–8 Feb.

The Flavor Delight aprium is in bloom, 11 Feb.

The blooming is not early, despite the January warmth. The almond depicted above usually has its first bloom around the same date in February: the 12th in 2017, 6th in 2016, 3rd in 2015. The Flavor Delight likewise tends to have its first several blossoms open around now: 14th in 2017,  7th in 2016, 15th in 2015.

What is somewhat more unusual is below-freezing temperatures at this time of year. (I am sure they were common at this point in February decades ago, but not recently.) The latest date of a below-freezing temperature in 2017 was 25 Dec. (29F, though it was 32 on 24 Feb.), in 2016 2 Jan., in 2015 3 Jan, and in 2014 5 Feb. And the current forecast calls for a few days of low temperatures in the 20s and 30s. This could be bad for pollination of the trees in bloom and for tender young leaf growth on the citrus and some other trees.

That is the nature of a Mediterranean climate–“spring” begins in early February, but winter can keep hanging on.

Fog and chill

It has been foggy in recent days. Far from my favorite kind of weather, especially when it sticks around all day.


Sometimes, however, it can be good for the chilling hours accumulation that the deciduous fruit trees need. It is the tendency towards multi-day dense fog events that has made the San Joaquin Valley (south of here) historically a good place for prunes, peaches, apricots, and other fruits that need winter chill to set well in the subsequent growing season.

However, this has been the case with this fog event only on one day, when we had a low of 39F and, due to the fog, the temperature did not reach 50 till after 10:00 a.m. Prime chilling temperatures are roughly 38 to 45, with some continuing but significantly diminishing value up to the lower 50s. So that day was a good chill day.

Not so much since. For the past two days, the temperature has just hovered in the 45-51 range. That’s pretty close to useless.

(I had been meaning to write about the fog and chill even before I saw that a reader had commented at a post that is almost 12 years old, with a question about chill. One of the things I always appreciate on this blog is people commenting on old threads. I almost never close comments, no matter how old the thread, unlike some other blogs out there.)