Yesterday I was out early, and the rising sun was just a small blood-red disk in a tan sky, the result of smoke and ash from more than 800 fires burning in California. The mountains around us are barely discernible in this haze, which resembles severe smog, and the sunlight has a brassy quality.

It’s cool now, but a week ago we had four days of 100-degree temperatures. That’s our third heat spike in what has been a fairly cool, windy and very dry season to date. We also had spikes in mid-May and early June, and this succession of heat events reminds me of the 2003 and 2004 vintages.

That said, the vineyards are showing nicely. We use two tools to monitor our water situation and evaluate the effectiveness of irrigations. The neutron probe tells us the levels of moisture stored in the soil. The pressure bomb, which we’ve had as an in-house tool since the 2002 vintage, gives us leaf water pressure, a snapshot of the water situation in the plant.

Of course, the data has to be interpreted. For example, these hot days have about a “two-bar” effect on our readings. Whereas the leaf water pressure might read 9 or 10 bars on a cooler day, a hot day will generate a pressure reading of 11 or 12, which would normally indicate considerable stress. So you have to consider the reading in context.

We did put on a little water given the natural increase in demand during hotter days. But the vines have cruised through beautifully. Shoot tips look good and canopies are holding up. Because of the frost and cool weather early in the season, we’ve had extra steps in manipulating the canopies, moving wires for slower shoot growth. At this point, we are positioning shoots and opening the canopies to light and air.

In terms of crop size, we are seeing less quantity but more open clusters, an indicator for high quality that means better color development in the berries. We’re seeing some shot berries in the Martini and Calera selections, more than in the Dijon clones. In general, the crop is looking very good.

Last month we looked at petiole (the stalk that joins a leaf to a stem) analyses. Each year at bloom time, we examine this part of the plant to determine nutritional status. This gives us a snapshot in time, and we also create a history so that we can compare readings year by year. The University of California at Davis has developed some good average values to help us interpret our data.

We look at the macro-nutrients - the NPK or nitrogen, phosphorus and potassium known to every home gardener. Nitrogen stimulates green growth, phosphorus affects fertility and fruitfulness, and potassium helps ripen fruit by affecting the transportation of carbohydrates. We also consider various micro-nutrients like iron, zinc, boron, manganese and magnesium, which also play key roles in the functions of the grapevine.

For the past few years, we’ve had slightly lower phosphorus values, but those have come up. We’re looking for any red flag so that we can correct the situation before veraison (when berries soften and turn color) to make nutrients available to the plant and enable it to perform properly. And right now, our vines seem to be doing just that.

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