Too much sun can be destructive to grapes and skin alike

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It was a tale of two pities weatherwise in the Walla Walla Valley this past week, as another rainy and cool episode rapidly gave way to a sizzling early-summer heat wave that has had residents begging for mercy over the last few days.

This dizzying turn of events illustrated quite nicely the fickleness of southeastern Washington weather. The week saw the normal June rainfall for the entire month (1.24”) exceeded by a good one-third of an inch. Afternoon temperatures that were at least 10 to 15 degrees below normal due to the moisture and cloud cover suddenly zoomed into the searing triple digits.

The culprit behind the roasting heat was a vast dome of high pressure that sprawled over a wide area of the West. Sinking air that was heated by compression combined with the most direct rays of the summer sun to produce a heat wave of epic proportions in several western states. This broke numerous records and caused much misery for millions of residents in a broad area that stretched from Arizona to Montana and California to Colorado.

In Las Vegas, the mark of 115 reached on Saturday tied a record, while the 119 recorded in Phoenix the same day fell a scant three degrees from equaling that desert city’s all-time high temperature. It was so hot there that for a time on Saturday afternoon, airplanes were not allowed to take off in air that did not have sufficient density to allow for safe liftoff from the ground. Excessive heat warnings were in effect over the weekend for parts of eight western states, and inhabitants were advised to take all precautions against the potentially lethal temperatures.

Your weatherperson was all too happy to heed the warnings, and spent the better part of the last few days reclined on his favorite couch engaged in a serious examination of the inside of his eyelids. There was a time — long ago — when he actually enjoyed such weather and even sought it out. As a graduate of the University of Arizona and a nine-year resident of Tucson, he earned a reputation as the “next George Hamilton” for the assiduous manner in which he cultivated his tan.

However, he was left with an unpleasant token from those magical years, in the form of multiple skin lesions of both the pre-cancerous and cancerous variety. The sun and its relentless heat have become his mortal enemies and have been added to the list of major annoyances in his life — a list that seems to grow longer now with each passing year: “flavored” ice tea (if you don’t like the taste of pure, unadulterated tea, you are free to drink those disgusting sports or energy drinks that have inexplicably become so popular recently); loud, ill-behaved children in any public venue, but particularly in any restaurant other than McDonald’s; and our numerous local Walla Walla drivers who insist on adhering to a speed exactly equal to one-half the posted limit.

How can someone who now finds himself sun- and heat-averse make his living outdoors in a vineyard setting? The key, of course, is to start early and end early. Here is a case where insomnia can be made to work for you: Arising at 4 a.m. in the summer can mean a return to the cool comfort of one’s well-air-conditioned office before it becomes truly unbearable outside.

Being the heat-loving plants that they are, grapevines are having the time of their lives in the current hot spell. With adequate water they are still lengthening their shoots and adding to the leaf canopy that will enable them to ripen their load of fruit this coming fall.

In addition to providing the energy for photosynthesis, sunlight offers other benefits for the vine. The UV light that comprises part of its spectrum is inhibitory to powdery mildew (as is the high heat), so we make an effort to open the dark interior of the canopy to light and air in an effort to decrease the shade and thereby lessen the possibility of disease.

Allowing some sunlight to hit the clusters is also a very good idea from a wine quality point of view, as it promotes good color and flavor development. Sunlight breaks down a compound called methoxypyrazine, which is responsible for some of the generally unpleasant bell-pepper flavors often found in deeply shaded, unripe fruit — particularly in some of the Bordeaux varieties like cabernet and cabernet franc.

In order to achieve a more open canopy, a certain amount of leaf removal is recommended, but this is an operation that must be performed with great care and in the proper manner. Pulling too many will expose the fruit to an excessive amount of sun, leading to possible sunburn. Leaves should be removed very judiciously — or not at all — on the west- or south-facing side of the canopy for the same reason. Earlier removal is better than late as it will give the berries a chance to develop a layer of protective cutin that will help them ward off some of the sun’s burning effects. If only your weatherperson could do the same.

The current heat wave will be relatively short-lived with Monday and Tuesday providing the worst of the hot weather, with high temperatures in the low 100s. The core of the high pressure system will gradually begin to slide to the southeast by Wednesday, leading to a bit of a cooling trend. Meanwhile, southeastern Washington will find itself in a southerly flow, and squarely on the so-called “ring of fire” at the periphery of the clockwise circulation around the high. Occasional impulses of moisture migrating north from Mexico may ride that southerly wind up through Arizona and Nevada and eventually find their way into Oregon and Washington.

The combination of a moist surge and serious daytime heating will serve to destabilize the atmosphere and possibly touch off a thunderstorm or two, before a cooler westerly flow drops our afternoon temperatures some 10-15 degrees by week’s end. It will still be quite warm — just not blazingly so.

For those who have been clamoring for some real summer weather, I hope you are enjoying it. For the rest of us, it should be remembered that October is now only three months away.

A lifelong fan of both the weather and the Baltimore Orioles, Jeff Popick is an instructor at the Center for Enology and Viticulture at Walla Walla Community College and manages the school’s teaching vineyard. Send your questions and comments to him at jeffrey.popick@wwcc.edu.

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