The Quality of Sun Light
By: Ralph de Amicis
Posted: Jan. 16, 2013

[Photo: Sun filters through a thick mass of grape vines / Credit:Kiley]

“Grapes are sunlight held together with water,” Galileo said. He had a good point there because vines create much of their fruit from sunlight, so the quality of light in the vineyards is an essential part of the terroir that shapes the flavor of the wines.


It is interesting how many great wine regions are valleys. Napa is a perfect example—a wide valley floor spanning two mountain ranges, tilted from southeast to northwest. This allows the cool, color-rich, morning sun free access to the valley floor, but shades it from the afternoon sun, which blasts the high eastern slopes full bore. The result is delivered in the big tannins.


But sunlight is about more than just direction. It is about color, moisture and beauty. In the Napa and Sonoma valleys, thick summertime fogs descend at night, coating the grapes with cooling dew and stopping the grapes from dumping their acid.


In the morning that fog still carpets the valley floor. The rising sun chases the fog back towards the bay, but as they interact, sunlight and moisture create rainbows of color that become micronutrients, which in turn create wonderfully complex flavors. One region where this is most evident is Stag’s Leap in southeast Napa. The Cab-Sauv blend from this little side valley blew the doors off the Judgment of Paris tasting in 1976.


This wonderful collection of little rounded hills and steep canyons was once considered a backwater. The small amount of land that was high and dry enough to support vines was run through with rocks and escarpments, making it hard to run a tractor in a straight line. Across the road was flat, but so low that keeping the vines dry in those heavy fogs was an iffy situation. Why plant this area when the land up-valley in Oakville and Rutherford was high, wide, flat and a lot less foggy—which makes sense if you are making a jug wine. But it’s well known that the best wines often come from the most difficult land.  


In Stag’s Leap the mountainsides face west where they receive hot afternoon sunlight for strong tannins. But, these little hills are planted all the way around offering a variety of exposures and flavors. Because Stag’s Leap is in the southern valley it spends many an early summer morning wrapped in fog, and those canyons and small valleys are very slow letting that moisture go. Their grapes are washed with rainbows most every morning resulting in a wine with wonderful depth and complexity.


Up valley in Oakville and Rutherford, on the rounded belly of the earth, in the protective shadow of Mount St. John, the vines bask in day-long sunshine, followed by a cool nighttime fog bath, which scrambles away early next morning at the first sign of sun. These are the “big reds,” drenched in sun, high in alcohol, which put the flavor over the plate no matter the thickness of the steak or the richness of the cream. At the far end of the scale, up on top of Howell Mountain, higher than the fog can climb, the hot, yellow afternoon sun bakes the vines, making them build tannins that keep them safe in their bottles for many years to come. They have the flavors of the afternoon, the rich colors of the setting sun, so they need many years to reach their best.   


When an area is filled with microclimates and unique geology it lets winemakers access varied flavors only a truck ride from their crush pad. Seeing and feeling where the wines begin is what makes these regions appealing to wine makers and so much fun as a wine tour destination.   


Ralph & Lahni de Amicis are tour guides, authors and television hosts in Napa, California

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