GEM avocados: Central Valley prepares to be our new avocado center

[KC6ZLV]

Originally Posted by tstieber

I agree with all the points, just that they apply more to citrus than olives at those temps you describe. I remember the historic freeze of 1990 and all the Havoc on crops and landscaping plants, but I never saw a single olive tree with any issues. That was in Inland Bay Area. Looking up olive trees again, it looks like most varieties tolerate down to 15 degrees before they sustain considerable damage, so my number he was off by about 5 degrees, but almost no commercial Olive growing region, and certainly not suburbanized parts of the stage, have sustained temperatures quite that cold ever. Even now, my parents have an olive tree in interior Northern California that is so vigorous that it can't be contained! Anyway, the Olive Ranch that I know the owners of personally have frequent hard freezes every winter near Paso Robles, much colder than it gets in the Central Valley, and they are not on Thermo belts at all. I think of olive trees as being pretty much fool proof in California. Of course, it is possible that a historical all time record freeze could damage fruit before foliage, as fruit is typically more sensitive than the trees on which they hang.

I posted a link about damage to olives from the freeze. I don't know why you want to discount those facts and insist your personal observations have more validity. Anyway, the point is there was extensive freeze damage to the olive crop that year regardless of disagreement with the possibility of freeze damage to olives.

[KC6ZLV]

Originally Posted by tstieber

Just had a chance to check out that link. Very interesting! I have no idea where Glen county is, but it sounds very rural. :-)

The Celsius temperature converted to Fahrenheit is just over 11 degrees Fahrenheit, so wherever that town is, it certainly got colder there than most of the Central Valley or even in land Bay Area. Keep in mind that Not only was the 1990 freeze the coldest temperatures ever recorded in California, which haven't been seen since, but also that this particular Town seems to be the coldest of all of them. I just looked up at Manzanillo Olive growing requirements, as the link said those are the least Hardy, and even those are Hardy to 15 degrees. Given that on average, the coldest temperature recorded each winter in California's interior growing regions is in the upper 20s, even that would be a consistently safe choice almost everywhere, almost all the time. And many of the growing regions have never been that cold at all. So I would not consider olive trees to be "sensitive" to frost in California, to the point where it would make sense to protect those trees from the types of frosts or freezes they are likely to get. Much more so for citrus, which is much more sensitive, but still is very common throughout the Central Valley.

There were numerous cases of temperatures down below 15 degrees up and down the San Joaquin and Sacramento Valleys. I think the coldest temperature recorded was 8 degrees. Monterey Bay Nursery had an article that appeared in one of the horticultural trade publications wherein the article stated 10 degrees was recorded out in the growing grounds, which I think is in Watsonville.

[tstieber]

Originally Posted by KC6ZLV

There were numerous cases of temperatures down below 15 degrees up and down the San Joaquin and Sacramento Valleys. I think the coldest temperature recorded was 8 degrees. Monterey Bay Nursery had an article that appeared in one of the horticultural trade publications wherein the article stated 10 degrees was recorded out in the growing grounds, which I think is in Watsonville.

If those temperatures were recorded, then they are obviously lower than the 15 degree hardiness of the most frost sensitive variety of olive tree stated in the article, although those temperatures seem to be the exception, as Sacramento's all-time record low is 17F, Redding's is 16 and Fresno's is 17, just to pick a few major cities up and down the valley. While there may have been some exceptions, much of the valley would have supported even the most tender varieties of olive trees in the coldest weather event in 150 years -- that's how tough olive trees are. My point is simply that agriculture isn't generally planned around all-time records of any sorts, or else we wouldn't grow any crops for fear of epic floods, droughts, heat, or cold. That's what insurance is for. Growers go to reasonable lengths to ensure optimum growing conditions, and with citrus being generally at least ten degrees less hardy than olives, thermal belts are more often used for citrus and not usually for olives, because for most of the valley, it would be overkill to bother protecting olive trees. This new GEM avocado will be hardy to between 15 and 20 degrees, possibly a moderate risk every century (or more) but worth growing for the odds being favorable. And also much hardier than most citrus.

So I'm not arguing with you that some olive varieties in some microclimates during the coldest snap on record suffered some damage (and most recovered), only pointing out that this would not be the 'norm' that would motivate growers to take precautions such as using thermal belts for olives when those growing areas are more valulable for other crops and olives would do just fine at the bottom of the valley.