Chill so far

When you are counting the chill hours that your deciduous fruit trees need, you don’t like days in January when the temperature is around 90. But yesterday was the first day of negative chill since 20 November, and we’ve had some remarkably chilly nights by Ladera Frutal standards. So, the chill count estimate sits at 276. Not bad for this early in the season.

And a good blast of cold air is on its way, beginning Thursday and then peaking Friday, according to this morning’s forecast Continue reading


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 38–45, 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).

Bananas in sunlight_19Dec06.JPG

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.

Fruit set in a wet spring

After hardly getting any rain all winter, we’ve had a very wet spring, with a series of storms–a few quite big–passing through in March and the first half of April.

The wet spring followed a winter with quite good chilling accumulation (despite some warm spells along the way that made a doubter of me). The Mesch Mesch Amrah black “apricot” (actually a plumcot) is always one of the harbingers of spring. It had a good bloom, and the early signs of a good fruit set. But the wet weather did it in, and nearly all the fruitlets aborted by the end of March.

Most of the real apricots, on the other hand, have set better than I have ever seen before!


I am not sure now which apricot this is (shame on me, I know). It could be ‘Earli Autumn,’ ‘Autumn Glo,’ or ‘Blenheim.’ It does not matter,* because all of them (and also ‘Newcastle’) look like this. Look closely (especially on the large photo, which you can open in a new window by clicking the image) and you will see several very dense clusters of fruitlets!

The ‘Moorpark’ (as I have said before, my favorite) is still blooming. Fortunately, there have been some good sunny breaks between storms (inlcuding an 85-degree day on Friday), and it looks like it is setting.


Just today I noticed that the ‘Canadian White Blenheim’ had some blooms and several flower buds that are swelling. I have waited a long time to taste a true white-fleshed apricot. Could this be the year?
Continue reading

Fruits in Biblical Times

I never imagined there would be a discussion at F&V about this topic, but it is Fruits and Votes, and we are in the midst of Pesach, so why not?

In an earlier planting I asked about the historical accuracy of apples in charoset, a key part of the Passover seder, given that apples are a fruit neither indigenous to the Middle East nor ripe in the springtime. Vasi provided a link about the possible origin of the custom in some interesting experiences the Israelites may have had in apple orchards in the Nile region.

The possibility that apples might have been in that part of the world at that time in history did not seem right. However, it could be so. On the apple and its ancient cultivation beyond its probable origins well to the north of the Biblical lands, see the history at Vegparadise:

Some historians report the apple’s origins were rooted in Southwestern Asia, just south of the Caucasus Mountains between the Black Sea and the Caspian Sea. Others note that apple seeds found in Anatolia were carbon dated 6500 BCE. Archeologists even found a fossilized imprint of an apple seed from the Neolithic period in England.

And so maybe apples really are traditional to the Exodus experience after all, as the link Vasi provide above suggests. Vegparadise again:

In the 13th century BCE, Ramses II ordered cultivated varieties of apples planted in the Nile delta.

I would not have expected apples to have been grown in that region, given the climate. This offers more evidence that apples–even old varieties–do not have a significant chilling requirement! (The Nile delta would not get much winter chill, and while the climate certainly has shifted and the region was not always desert, it was also not temperate, but rather probably tropical around Ramses time. By the time of the Exodus, it had probably largely completed its transformation to desert.)

Even if apples were known to the ancient Egyptians and Israelites, there is still no way there would have been fresh apples to eat at the original Passover, assuming the first one really took place in springtime.

This discussion inevitably leads to the question of what Eve’s fruit of temptation might have been. I would guess pomegranate. The Vegparadise page agrees, but also suggests maybe quince. Quince seems unlikely, given its non-Middle East origins, but if apples could grow in the Nile delta, quince certainly could grow in the Tigirs delta, as they have quite low chilling requirements. However, quince are almost certainly also from much farther to the north, so presumably human traders would have been required to bring quince into the region. That somehow does not quite fit with the whole Genesis/Adam & Eve story, does it?

The weather is weird

I often say the weather is weird here in Southern California, home to moderate temperatures somewhere between mild temperate and subtropical. But this winter–about to end, according to the calendar–has been weirder than most.

After not having a single day when the high temperature was below 60F through February 17, we have had seven since that date, including 51 on March 11. That was the lowest high I have seen in over a decade of daily temperature record-keeping in Carlsbad (by the sea, where highs below 60 are more common than here, but highs below about 56 much less so) and Ladera Frutal. The day at 51 (most of the daylight hours of which was spent between 45 and 47) was during that storm system that was promised to be cold, and it delivered. As I have lamented before, such weather would be great in January, but is somewhere between useless (for the deciduous trees’ chilling accumulation) and harmful (for already-open buds and for the subtropicals) when it comes in March, after warm weather in the previous months has gotten things growing again.

About the chilling. Even before the mid-March blast of cold air, we had certainly reached 600 hours in the open air of the lower reaches, and perhaps 650+ in the “cheat” zone. And the Moorpark (600 hours needed, say the catalogues) is gearing up to bloom!

Late winter wonders

This is a forecast I would love to see in January. But for March, after almost everything has had its chilling requirement met and, on account of some very warm spells many things are in bloom (see the two previous fruits.laderafrutal posts), this (from the 2:50 a.m. release of this morning’s NWS San Diego forecast discussion) could be quite bad news:


We’re not likely to be one of those inland valley/foothill areas with snow, but it could be cold. And hail is really bad news for fruit trees in flower.

The blooms of March, part 1: A high (?) chill apricot

Apparently, we got some decent chill after all!

Look at this branch of the Earli Autumn apricot, which the catalog says needs 800 chill hours. (And don’t adjust your set: The digital camera insisted on focusing on the relatively bare branch behind.)


Now, there is no way that we got 800 hours, and thus no way that this variety really needs 800 hours. A requirement of 500 hours is probably closer to reality, and 500 is probably more or less what we had reached as of around two weeks ago (when this trees’ buds began to swell, indicating their chilling needs had been met).

When you see a branch like this, with every bud about to burst, you know the tree is happy!

But as the photo on the “inside page” shows, the upper portion of the tree is not singing quite as loudly about the arrival of spring. Continue reading

Low chill cherries?

In the last few weeks, I have noticed on several checks of my Sitemeter details that quite a few folks have found F&V via a search for “low chill cherry.” This planting is for you.

Yes, there are low-chill cherries! They might not be the heaviest bearing in our climate, but I can attest that you can grow cherries here! ‘Stella’ and ‘Lapins’ are said by some not to require chill at all. This may be true of other self-fruitful cherries as well (i.e. those that do not need to be cross-pollinated). And a new variety, ‘Royal Rainier,’ is listed by Dave Wilson Nursery as needing only 400 hours. The flavor of the ‘Royal Rainier’ is spectacular!

I have had both ‘Stella’ and ‘Royal Rainier’ fruit here, but then the winter after which they fruited probably experienced 550-600 chill hours at the bottom row where I “cheat” on chill. I also had ‘Stella’ fruit one year in the usually lower-chill environment of Carlsbad, but that was an unusually cold winter (maybe 600 hours). In other words, I cannot personally vouch that these will fruit at 400 (or less), but there is growing evidence from experience by various growers that at least these three varieties just might be suitable to mild-winter climates.

I am still evaluating other self-fruitful varieties, including ‘Craig’s Crimson’ (a top taste-test scorer, but no bloom since planting three years ago) and ‘White Gold’ (a Stella cross that I planted a year ago) to see if they might fruit here. I also have a ‘Bing’ (700 hours and not self-fruitful) just for the fun of it. So far, the ‘Bing’ has not bloomed, but it is growing well. Often deciduous trees that do not get their nedded chill will not even have good foliar growth, so I am still hopeful that the lushness and vigor are harbingers of fruit as the tree matures.

Winter chill: Can you lose it?

At the propagation bench, Doug asks a good question: How can you lose chill hours? It is not that you lose them. As I mention in the planting to which Doug was responding (and also the subsequent one about the return of winter), nothing gained in chill is lost. If you reach 400, no matter how warm it may be between the day you got to 400 and the time the tree is ready to break dormancy, you’ve got your 400.

But the question really comes down to the following. If you have 400 on some date, and then it gets very warm, and then later there is another cold snap (like right now at Ladera Frutal), what is your total chill accumulation at the end of the cold snap?

Let’s say you have 400 hours, and then the warm spell is a net –50. Then the next cold snap is another +100. Then it warms up for good. How much chill did you get for the winter?

400? 500? 450?

The best answer (though one cannot say “right” because these are all just estimates anyway, as even the experts admit) would be straightforward arithmetic:


In other words, you did not lose anything. In fact, you still had a net gain. But you can’t add the 100 on top of the 400, without accounting for the week (or however long it might have been) of negative chill.

I like to think of the negative hours as marking time. Warm spells in winter put the tree closer to breaking dormancy, whether or not its chill requirement has been met. So, those 50 negative hours make it harder for the tree to meet its 500 requirement, but if the warm spell is not too long, and you get that late cold snap, there might still be time to get back on track for 500. But now you need 150 since the previous peak, not 100.

That’s why it is so hard to get 500+ chill hours in most of southern California. It is not that it is not cold enough. It is that you get a sequence of cold, warm, cold, hot, cold, etc.

And then winter returned

Just over a week ago, in commemoration of half a year of blogging here at,
I was ready to give up on winter. Then this morning we were treated to its return!

Frosty Feby 20, 2006

No, those aren’t patches of snow under those deciduous trees just outside the corralito, but there was a pretty good frost this morning, and even as late as 8:00, the areas shaded by the grapefruit trees still were frosty.

I had feared we’d never get to 500 chill hours, which is the minimum required by many of our deciduous fruit trees. Chilling, by my estimate, had reached about 406 on Feby. 7, and then came the big warm up. In fact, for about a week we had classic southern California fire weather.

After the Feby 9 fire, south wall, Moosa Canyon

Not only fire weather, with the high temperatue breaking 80 six times in a nine-day span (and reaching 90 twice), with low relative humidities in the single digits, but an actual fire. The photo above is taken about a week after a fire on the canyon wall opposite the house. I was not here when the fire occurred, and did not even notice it till my grove worker pointed it out days later. But that’s a scar on the canyon wall that will be there a while. (At the bottom of the canyon is, or was, a small seasonal lake in the creekbed that the fire-fighting helicopters nearly drain whenever there is a fire in the area. It is quite an operation to watch. Yes, SD County finally invested in fire-fighting helicopters after the disastrous fires of October, 2003.)

So, about that chill. Even after a week of fire weather, we’re back up to 460 hours, having bottomed out at 389 during the warm spell. We had not had a day all winter long when the daytime temperature peaked before reaching 60, and now we have had two in a row, with another likely today. (Highs below 60 are not very common here, but most winters we have a few such days in late December or in January.)

With a week of cold nights and moderately warm days forecast, we might yet break 500 hours! And, despite a few blooms here and there, most of the higher-chill varieties appear to have remained dormant. (In warm spells late in the winter, even trees that have not met their chilling requirement sometimes send out a few blooms, as if to say “we think it might be spring,” but if they start pushing out leaf buds before the chill has been avhieved, they will not bloom well and thus may have little or no fruit. Several trees with chill requirements estimated at 5-600 hours have had a bloom or two since the first few days of this month.)

The low chill stuff is all a-bloom by now, and you can see the Tropic Snow peach in the second photo: Just look for the profusion of pink just above the white fence on the slope. By now, it is past full bloom. Still holding out hope for the stuff down at the corralito.

Half a year of Fruits and Votes: From ‘The Last Pluot’ to wondering if we’ll get any pluots this year

Fruits and Votes just completed its first six months of existence. The first post in the fruit block (actually a bit under six months ago) was about the last pluot of the 2005 season. Now, with a very warm week having come to an end, it seems that the chill count that started in early December has probably come to and end. Will we get any pluots in 2006?

This was quite a mild winter, even by our standards. And while we could still get more chill hours before some varieties break dormancy, the warm spell (up to 90 one day, and four straight over 80) means quite a setback in the accumulation of chilling. At this point, I would estimate the peaks to have been 200 up high on Ladera Frutal and 400 down at the bottom of the hill. That is, of course, an amazing difference, and really shows how elevation matters. These two locations are not far apart horizontally, but are separated vertically: the lower portion is over 150 feet lower on a steep slope than is the upper location.

Still, 400 is not enough for many of the varieties planted down in a location that is expected to get 500 or more. With 404 hours of chill having been reached, according to my calculations, on 8 February, we are now back closer to 390 after the warm spell. Any variety growing down at the elevation for which 400 is sufficient has thus had its chilling requirement satisfied, but the prospects for further significant gains above 400 seem bleak this late in the season. Up higher on the slope, the 200 peak was reached on 5 February, and with the warmer nights higher up the hill combined with the warm days, that location is at only 166 hours now. Surely, chilling accumulation has ended there, but most of the varieties planted there require 300 or less. (The Arctic Star nectarine is listed at 300 hours in catalogs, but looks ready to burst into full bloom, so it must be lower.*)

Some varieties of pluots need 500 hours, and so we might have a lighter crop this year. It is possible that my “cheating” on chill has allowed the row closest to the taller grapefruit trees to have obtained closer to 500 hours.

And there are some encouraging signs. There is a bloom already on the Autumn Glo apricot, a late-fruiting variety that is said to need at least 500 hours. There are also several blooms on one pluot, the Geo Pride. So far, these varieties–both of which are located in the cheating row–are not showing a lot of swelling buds and so it remains unclear whether they will bloom fully, or are just sending out “feelers” to see if spring is really here (groundhog blooms?). Even without adequate chill, a stone fruit tree will break dormancy when it has accumulated some (unkown) number of “warm hours” whether or not it has had the adequate accumulation of chill hours. But only with the chilling requirement met will it bloom fully and set a good crop of fruit.

* Assuming my estimation technique is reasonably accurate. Given many years of experience with it, I think it is as good as any other estimates available.

Spring already?

Spring can come rather early here at Ladera Frutal. The Tropic Snow peach is one of the bellweathers of spring, as it is always the first of our varieties of deciduous tree fruit to bloom. This photo was taken on January 27.

Tropic Snow first bloom 2006

If I were to grow only one peach it would be Tropic Snow. It is very low chill and thus can be grown practically anywhere–perhaps not literally in the tropics, but certainly in southern Florida or interior Hawaii. (Its low-chill character could cause it problems in colder regions, however, as it might bloom too early–though not in January).

The fruit is white-fleshed (hence ‘snow’) and melting (also like snow!). It is not a keeper or a shipper, and so you are not likely to see it for sale anywhere, even a farmers market. You pretty much have to grow it yourself. The flesh is extremely juicy and luscious, with a tart lemony character to go with classic white-peach flavor.

Its listed chilling requirement is 100-200 hours. It clearly is not more than 100, as the buds started swelling on January 10, at which time its location up here on the slope just below F&V Central was probably barely 100, if that. In the photo can be seen not only a couple of blooms, but a whole series of swelling buds. It will be in full bloom in the first days of Februrary, and we can expect the first fruit in the second half of May. The photo also shows the wildflowers in bloom in the irrigated ares of the slope among the bay rum, curry leaf, pitanga, cherimoyas, sapodillas, and other trees.

Much more surprising than Tropic Snow bud swell on January 10, is Newcastle apricot bud color in late January.

First Newcastle red buds 2006

The Newcastle is one of the very best apricots. Most sources claim it has a chilling requirement of 500 hours, but clearly those sources are wrong. A tree that had been planted at our house in Carlsbad by the original owner in 1975, a mile or so from the coast, fruited annually, even in years when the local chilling accumulation was probably no more than 350 hours. The tree in the photo is grown from a scion of the old tree we left behind in Carlsbad and is planted in the corralito at the lowest part of Ladera Frutal. Down there, the chilling accumulation is much greater than in the upper reaches of the slope, which is why the corralito planted with apricots, pluots, cherries, pears and higher-chill peaches is located there. Even so, the chill received down there as of a few days ago when the buds started to swell was probably under 350 hours. The cluster of buds that are swelling may be doing so because the cluster is at the end of a branch that was pruned. That is one of the reasons we prune during dormancy–to stimulate growth and flowering the coming year. So the reddening of these buds is not a gaurantee that the tree has had its chilling requirement met, but their presence is certainly encouraging.

Newcastle is thus the variety I most recommend to people seeking to grow apricots in low-chill areas. Most nurseries recommend Gold Kist, but aside from being a much less flavorful apricot, Gold Kist was much less reliable than either Newcastle or Royal in Carlsbad. Katy is also sometimes recommended as a low-chill apricot, but it too appears to be more spottily productive even here (I no longer grow Gold Kist) and Katy is also a subacid fruit, and what’s the point of eating an apricot that lacks acidity? I recently saw a variety called Tropic Gold that is alleged to be low chill, but I know nothing about it (and amazingly I neglected to buy a tree, though I still may go back and get one in the name of science).

If Tropic Snow is blooming and Newcastle is gearing up, pitchers and catchers must be getting ready to report!

More cheating on chill

On December 22, I noted how one can take advantage of the lower position of the sun in mid-winter and plant deciduous fruit varieties near tall evergreens in a way as to maximize the accumulation of chilling hours. That post contained a photo of the hedgerow located within the corralito, which is itself located within the grapefruit grove at the lowest part of the finca.

Hedgerow Closeup Jan 5, 2006

The above photo is a close-up, taken today, of the middle portion of the hedgerow after I pruned the trees. Notice that the lower and back-side branches, on which I was careful not to prune off too many flower buds, remain in shade, even though the upper parts of the trees are in sun.

The tree in the foreground is a Moorpark apricot (the best, in my assessment). The two beyond it are Earli Autumn and Autumn Glo apricots. The latter two are new varieties with an unknown chilling requirement, but probably over 500 hours (but certainly not the 800 shown in the Bay Laurel Nursery catalog). Moorpark probably has a chilling requirement of around 600 hours, which is more than we can count on accumulating over our short and mild winters. However, by maximizing winter shade, one can obtain more chill than would be the case in a location that remained sunnier in the winter months, and thus can greatly expand the range of varieties that can be grown.

All three trees fruited last year, and all the fruit was on lower or back-side branches. Chilling accumulation works through the individual buds, not the tree as a whole or the roots.*

Today around 11:15 a.m. when the photo was taken, the temperature differential between sun and shade was enormous: 79 in the sun, but only 71 in the shade. The termperatures will converge somewhat later in the day, but the difference in late morning indicates how much more slowly the shaded area warms up. [UPDATE: The temperatues did not converge. The high in the shade was 82, while out in the open it was 89. I should have known: shade/sun high temperatures converge less the lower the humidity.]

In December, 2004, the average lows and highs were 43 and 67 in the sun, but 41 and 66 in the shade. For January, 2005, the figures were 44/67 versus 43/65. (The lows are affected as well as the highs partly due to the large trees trapping cold air that keeps on flowing downhill out in the open, but also because with less daytime heating, the shaded region also does not stay as warm overnight.)

This difference of a degree here and there may not sound like much, but can accumulate to 100 or more estimated chill hours for the season compared to what the electronic half-hourly count indicates for the thermometer in sun. The greater chill is at least as much a product of the slower warm-up in the shaded area as it is of differences in the ultimate high (or low) temperature over any 24-hour period.

Below is the manual thermometer that I keep in the shade of some grapefruit trees just outside the corralito.

Manual thermometer

The photo below shows the electronic thermometer that relays to the Davis Instruments Weather Pro console (and ultimately to the Ladera Frutal computer station) and proviudes half-hourly termperature readings used to compute chilling accumulation.

Weather Link network

Note that while this thermometer, visible on the pole to the right of the photo, is in the sun, it has a plastic shield around it. This prevents sunlight from shining directly on the sensor and giving a false reading. In other words, it ensures that what is being measured is ambient air temperature and not the intensity of reflected solar radiation.**

The above photo (more easily viewed in a larger version) also shows the networking system that transmits the data up to the office. Off to the far left of the photo is a second temperature station (as a backup) on a pole that is slightly askew (and almost obscured by the white trunks of grapefruit trees that have been cut down for re-grafting). On the lower part of that pole is a wireless data repeater. Also visible through or between native shrubbery up the slope are three other posts (some of white PVC) on which other repeaters–five in all–are arranged to relay the data.***

This is shaping up to be a much lower-chill winter than last, when we reached around 550 hours according to the half-hourly data transmitted through the network (and thus perhaps 650 in the shaded area). As of the morning of January 1, 2006, we were sitting at around 174 hours at the lower part of the finca (and 68, with a prior peak before the warm spell of around 95, up here in the more subtropical climes of F&V HQ). A year ago by January 1 we were already closing in on 300 hours below (and 190 at the office). Unless a good cold snap comes soon, the higher-chill varieties are unlikely to fruit next summer. Thus it is a good thing I have planted lower-chill varieties, too, to the extent possible.

One last photo below shows a Hunza apricot, which I planted last January. The Hunza comes from the high moutain valley of the same name in Pakistan. This tree is outside the corralito, but nearby. Notice how it is planted at the edge of a shady area. As it grows, much of the tree will be shaded. Hunza probably has a very high chilling requirement, but given how fantastically sweet and toffee-like the dried fruit of this apricot is (and with an edible kernel, too, with reputedly cancer-fighting properties), it is worth experimenting with.

Hunza tree, Jan, 2006

*I mention roots because I have heard of people packing ice around deciduous plants to maximize bloom, but freezing the soil is hardly useful to buds located some distance above.

**Always be skeptical of news reports in summer of intense heat on the pavement or an artificial-turf field; placing an unshielded thermometer on a hot surface reveals that the surface is indeed hot, but tells you nothing about just how hot the air, which is what actual weather data are based on.

***Only matters of practicality, and unwillingness to invest in a chain of 8 or more repeaters, keep me from having an electronic thermometer located back in the shady region of the hedgerow. The elevation of the electronic station is the same as that of the corralito, and that is the most important factor; it just means that my electornic data are more representative of the sunny portion of the corralito than of the winter-shaded hedgerow.

Cheating on chill

Here is one way to create a cooler microclimate effect:

Shady hedgerow on Dec. 22

This is the hedgerow down the hill, on the coldest part of Ladera Frutal, where I have my corralito planted with deciduous fruit trees. In a low-chill region, one can maximize one’s chances of getting fruit by “cheating” on the chill hours. One way to do that is to plant one’s highest-chill varieties (like the cherry and apricot varieties depicted here) in an area where they will be shaded in the winter. Naturally, one has to avoid the trees’ being shaded in summer, when sunlight is needed to ripen the fruit.

One way to accomplish this is to plant close to taller evergreens, as with the mature Marsh grapeftuit trees than can be seen on the exterior of the corralito. When the sun is low in the sky, as on this first full day of winter, only the tops of the trees will be in sun. But when the sun is higher in the sky in summer, three trees will be bathed in sunlight except at their very low back sides.

The hedgerow style of planting itself helps with the chill, because the dense planting trees help trap cold air (further aided by the groundcover seen here), while the dwarfing that results from the trees’ crowding one another keeps most of the fruiting buds low to the ground. The ground remains significantly colder in winter than the air a few feet above. After I prune this hedgerow in the coming weeks, all the trees will be shorter, as I will leave only the low branches.

Along this hedgerow, the overnight temperatures often can be a degree or two colder at night than is the case out in the open, and the shade keeps the daytime high a few degrees cooler, too. A few degrees here and there, over three months, can add up to a hundred or more chill hours, making the difference between no fruit and a good set on varieties marginal to one’s climate.

Chill count begins!

Well, the heat wave is gone at last, and the forecast promises a chilly weak ahead. Today’s low down at the bottom of Ladera Frutal: 38. Up at the summit: 45. Today marks the first day of the 2005-06 winter season in which we will accumulate chill hours. Deciduous fruit trees–apricots, peaches, plums, etc.–require an accumulation of “chill” before they will bloom and set fruit the following spring. This is one of nature’s fascinating evolutionary adaptations. It serves to keep a tree from budding after a mid-winter warm-up only to have frost or freeze later kill off the blooms and thus the fruit (and, more importantly from an evolutionary perspective, the seed inside). Continue reading