Chilling

I am into modeling.

I would show you pictures of my work, but there are likely legal ramifications that I do not care to risk.

Oh, not this kind of modeling

Image Source: The Fashion Spot
Image Source: The Fashion Spot

but the considerably more interesting and equally glamorous, this kind of modeling.

Regression Model
Image Source: Economic & Social Research Council. I do not work here.

As the last leaves of our apple tree (which is a very late variety called Garden Delicious) are falling, I started wondering about this year’s harvest and chilling hours. 2014 was a very warm year, and while the weather these days is nippy, we had warm days all the way through Christmas Eve. With the sort of freakish coincidence that is common these days, CNN’s Breaking News announced just now that 2014 was Earth’s warmest on record. While one year of warmth does not make a trend, it did make for a welcome change – we could enjoy being in the garden without needing to dash inside for jackets as soon as the sun set.

Our fruit trees, apple, Asian pear, plum, cherry, peach and persimmon, all need a certain number of hours of chilling to bloom, leaf out, and set fruit successfully. I am worried that if we do not accumulate enough chilling hours by the time of the normal bloom season, we’ll have low fruit set and poor leaf growth.

The UC Davis Fruit & Nut Research & Information site has a wealth of information, models (hence the reference to modeling) to calculate accumulated chilling hours and data from weather stations throughout the state. The station nearest where I live shows that this current season, which runs from the beginning of November through the end of February, the chilling hours accumulated is less than half of that this time last year.

My apple tree and Elberta peach tree both have chilling requirements of 600 hours, from the Dave Wilson Nursery website. Since we are midway through the season, and at just barely over half the minimum chilling needed, there is a chance that the trees might bloom unevenly, or flower buds may not open at all. This is disappointing since fruit of both trees is delicious. The implications of a warm winter for those growing fruit commercially is very serious. Central Valley farmers had half or less than their normal harvest last year.

There isn’t a way to get around volatile climate changes of course. Planting low chill varieties brings with it its own set of problems – buds opening too soon and getting damaged by frost and that sort of thing.

Most of us here lead lives far too busy to even step into our backyards, let alone care about what goes on there with regards to chilling hours, bee populations and other horticultural concerns. If fruit trees produce poor harvests year after year, for no fault of theirs, fewer people would be interested in planting or keeping them in their backyards. While most people would never grow fruit trees with the sort of interest bordering on obsession that I do, a gnarled apple in the yard, a little strawberry patch are simple pleasures that we would do well to hold on to as long as we can.

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