Looking at the latest update on the Blue Diamond site, it is...

Looking at the latest update on the Blue Diamond site, it is clear that the almond bloom in California is quickly winding down, with only a tiny number of flowers now remaining on the nonpareil trees.

Given this, it is probably a good time to take a step back and try to get a handle on the possible implications of the bloom time conditions on the eventual crop.

There were two major meteorological factors that could potentially influence the crop size this year: firstly, the 'pineapple express' that soaked northern California not once, but twice, during the bloom period. The first of these arrived just days before the start of the bloom, and the second storm hit between late February and early March.

The second factor was the very poor pollination conditions, due to both rain and unusually cold temperatures, that impacted California over the first ten days of the bloom.

Rivers of Rain

Northern California was hit by the second major atmospheric river from about the 25 of February onwards, and it lasted well into March, with the largest volume of precipitation falling over the first few days.

We know from local Californian news reports that, once again, some almond orchards were inundated by this recent deluge. The below photos show some flooded almond orchards near the town of Chico, in Butte County:


There is some evidence to suggest heavy precipitation in February and March can impact almond yields: looking over a chart of Californian almond yields between 1970 to 2010, those years which saw the largest drop in yields (1983, 1986, 1995, 1998, 2000, 2005) also experienced heavy precipitation between the middle of February and the middle of March in most of the almond growing regions of California. The threshold seems to sit somewhere between 75mm and 100mm, and it would seem that if upwards of 75mm of rain falls in a region between mid-Feb and mid-March, this is bad news for the crop.

I've drawn up a table, below, highlighting the volume of precipitation that was recorded by various weather stations near almond growing areas of northern California between the 25th February and the 8th of March. Note that Modesto and Stockton, located in Stanislaus and San Joaquin counties, are generally considered to fall in the central almond growing region of California.



In three of those six locations -Sacramento, Yuba City and Oroville-, the precipitation recorded was probably high enough to spoil the crop. As can be seen above, Chico and Stockton are also worryingly close to that 75 mm threshold.

Keep in mind that when this latest round of rain hit, many orchards were still saturated from the storm during the middle of February, which dumped similar volumes of rain across northern California. With this in mind, it is possible that Chico and Stockton might have also seen too much rain over this period.

In some respects, the weather conditions during the almond bloom in northern California this year were comparable to those seen in the last 'wet' year, 2017: Both years saw atmospheric rivers dump vast quantities of precipitation in northern California in the early months of the year.

The key difference was in the timing. In 2017, most of the rainfall fell prior to the commencement of the bloom, in January and early February, whereas this year northern California received a soaking from the heavens while the almond bloom was in progress.

Although the excessive rain in 2017 mostly fell before the bloom period, fields across much of northern California were saturated for months afterwards, and I am sure that this had an adverse impact on the crop in the north that year.

This year, the rain likewise flooded many areas, but because the precipitation fell during the bloom, it also likely had a disruptive impact on pollination. This suspicion is supported by a comment from an almond grower from Colusa, one of the northern almond growing counties, that was included in the March 1 Blue Diamond pollination update:

...“With nonpareils being close to 80% and so few pollination hours so far, I am not very optimistic on the potential of this crop. Today was our first good day in weeks.” Said Mike Doherty, member-grower in the Arbuckle area, “We will just have to wait and see but one positive thing is that overall at this time there is no disease pressure.”

In other words, while the 2017 almond crop in northern California wasn't great, this year is likely to be worse because the rain that caused the widespread flooding arrived at a very inconvenient time, while the almond bloom was underway.

It should be emphasised that less than 20% of the almond acreage in California is located the northern counties of the state. Even so, some growers in the central and southern areas are also concerned about the bloom-time conditions this year.

Pollination Conditions: Central and Southern California

The concern expressed by that northern almond grower is echoed by a grower near Bakersfield, in the far south of California's almond growing region, as noted on the March 6 Blue Diamond update:

“It’s hard to tell how bloom turned out. With more wind and rain than normal, we had reduced opportunities to pollinate the crop,” said John Allen a south Bakersfield area Blue Diamond Grower. “I’m always hopeful we’ll make a good crop, but I have my reservations this year.”

Allen’s sentiments have been echoed throughout the state. It was difficult for bees to get consistent hours during the season and on most days, bees would have to start and stop around rain events. However, with warmer temperatures associated with most of the storms, bees were able to accumulate hours in most regions. The weather in the coming weeks will help determine what percentage of flowers stay on the trees as nutlets. An almond tree can typically only retain 20% to 40% of the flowers after pollination. Sunny, warm weather assists in retention.

It is not unusual for almond growers to express reservations about the bloom-time conditions in California, but often such concerns prove to be misplaced. A good example of this was earlier this decade, in 2011, when many farmers were despondent about the potential impact of adverse bloom-time weather on the crop, but as it turned out, 2011 proved to be a bumper year, with a 2 billion pound almond crop, around 20% larger than the crop of the previous year.

So, we need to ask the question: are the growers who have been complaining about the pollination conditions being too gloomy?. Is it possible that, despite all the pessimism, the Californian crop in 2019 might surprise on the upside?.

I decided to investigate this question, and so looked at the first ten days of the almond bloom in 2019 and compared these to 2011, a year that, against all expectations, proved to be a year to be remembered.

The number of bees venturing outside of the hive on any day is determined by a number of factors- wind, rain, and sunshine- but maximum daily temperature is one of the most important variables.

The tables below compare the daily maximum temperatures at Fresno and Bakersfield over the first ten days of the almond bloom period, in 2019 and 2011.



Bakersfield and Fresno are the county capitals of the two largest almond growing counties in California, Kern and Fresno. So I think they would be broadly representative of conditions in the central and southern almond growing regions.

As can be seen in the table above, the average daily maximum temperature at Bakersfield over the first ten days of the bloom this year was only 12.6 degrees Celsius, a full three degrees below the average temperature measured in the same location and for a comparable period in 2011.

At Fresno, it was even colder, with an average temperature of only 11.9 degrees in the first ten days, just over two degrees below the average for the same period in 2011.

What is concerning about this, is that in both Bakerfield and Fresno, the average maximum temperature for the first ten days lingered below 12.77 degrees. Sub 12.77ºC temperatures can prove perilous for bees venturing outside the hive. As the Scientific Beekeeping website notes:

...A bee can raise its thoracic temperature roughly 30ºF above the ambient temperature while it is flying. That means that if it is flying in 55º (12.77ºC) weather, that once it leaves the warmth of the hive, it will barely be able to keep its wing muscles up to their minimum operating temperature (85ºF) (29.4ºC)—hence bees don’t fly much at temperatures below 55 degrees. And if they do, they often don’t return...

In short, all those Californian growers who have been complaining about the lack of bee activity this year weren't just imagining things. The pollination conditions really were fairly terrible this year, and certainly worse than those experienced in 2011.

I should note that those tables above only recorded the temperatures for the first ten days of the bloom period, and both Fresno and Bakersfield experienced some very good pollination conditions in the last days of February. Then again, it is clear from numerous local media reports that there was a shortage of bees in California this year, and although this would have impacted only a minority of growers, you have to assume that a shortage of bees and poor bloom-time weather conditions can't be great for pollination.

Conditions during the last rainy year in California, 2017, bore some similarities to those in the early months of 2019. Both years saw flooding in the northern counties of California, for example.

But it is fairly clear that the bloom-time conditions this year were more problematic than those of 2017. The rain proved more disruptive, falling during the pollination, and it was significantly colder in all of California's almond growing areas. If all things were equal, you would expect the almond crop this year to be smaller than the 2.27 billion pound almond crop produced in 2017.

Of course, all things aren't equal, and we have to also take into account the more favourable Californian orchard profile, with the numerous almond trees planted in 2016 producing for the first time this year, as well as rising yields on the trees planted in preceding years. I would guess that this would add about 5% to the crop all up. Given that the crop last year was so woeful, you might also expect a bit of rebound in yields this year, although there are never any guarantees in farming.

I wouldn't want to gamble a guess on the potential size of the Californian crop at this early stage, not least because there is such a big question mark hanging over it. This year, fairly dismal bloom-time conditions coincided with a bee-shortage, and I don't think we have ever seen that before in California.