Hourglass Vineyard Descriptions

Peering through the glass turret of a helicopter hovering at about 400 feet, you can see how two parallel mountain ranges—the Mayacamas to the west and the Vaca to the east—funnel together in dramatic fashion to form the hourglass-shaped Napa Valley. It is from this unique vantage point that we can begin to understand the magic of the vineyard that lies precisely at the narrowest point between the constricting mountains.

It was in 1992 that Dr. Kliewer first described the singular positioning of the vineyard to Jeff Smith and its equally exceptional geography. Dr. Kliewer knew the “hourglass effect” would play a significant role in defining the yet-to-be-planted Cabernet vineyard, but he could not articulate exactly how. He explained to Jeff that the Smith family’s vineyard defined the pinch of the hourglass-shaped valley and advised him to pay attention as he farmed the vineyard over time. In 10, 15, or 20 years, maybe they would figure out what it meant.

A Cool Breeze
Some 10 years after replanting the site, Jeff and his mother took a walk in the vineyard together on a summer afternoon. Jeff commented on how hot it was, and his mother replied, “Yes, but this little knoll will start cooling around 4:00 p.m. You can mark your watch by it.” “How’s that?” Jeff replied. “We get a nice, cool breeze here just about every day in the late afternoon,” she explained. “It really cools the knoll and makes it a very pleasant place to live.” Dr. Kliewer’s intuition revealed.

The constricting mountains were the cause of a thermal dynamic. As the northern region of Napa Valley warms, it creates an inversion that draws cooler bay air up from the south. The larger air mass gets pinched by the constricting mountains, and eddies at the narrow crossing where the Hourglass Vineyard is planted. In turn, the back-flowing air creates a cooling breeze that tempers the late afternoon heat.

Temperature & Grape Ripening
But how does this translate to bottled wine? First, we must consider that temperature is a key component in grape ripening. As the accumulation of heat over time increases (known to winegrowers as “growing degree days”), grape chemistry changes. Red grapes turn from green to purple (a transition called veraison), sugars rise, acidity falls, pH changes, polyphenols (complex grape chemicals affecting flavor, aroma, and texture) continue to develop, and seeds lignify as their tannins mature. Pick the grapes at the moment when all these elements reach the perfect balancing point, and wine magic is achieved.

The trick is achieving the perfect balancing point, and vineyard characteristics play a significant role in defining this dynamic. Once the skins have turned purple, the first sign of maturity in grapes is the arrival of sugars driven by heat and sunlight over time - the more heat and time, the more sugar. In reverse proportion is the decline of acidity. As sugars rise with heat, acidity falls. Consider this phenomenon the front end of the grape maturation cycle.

The back end of the cycle is where the magic of Napa often happens. You may hear winemakers refer to “physiological ripeness.” What they are referencing is the “back end” of grape maturity, when polyphenols develop and tannin is mastered. Often the back end happens weeks after sugars arrive, thus the warmer the climate, the greater the propensity for chemical imbalances. If there is no cooling effect to offset heat, sugars will continue to rise and acidity will fall as you wait for the back end to catch up. The results are either wines with high alcohols, high pH levels, and low acids, or more tannic wines with green herbal characteristics and less explosive flavors, depending upon when the grapes are harvested. Needless to say, balance is a critical component to farming great wine.

Napa’s Diurnal Climate
Napa is a magical place to grow grapes as most of it benefits from a diurnal climate. This unusual climate is a function of mountain ranges uniquely positioned between the cool Pacific Ocean and the warm interior valley of Sacramento. Warm daytime temperatures, which often reach the mid-90’s or higher during the growing season, draw in coastal fog at night. It is not uncommon in a 12-hour cycle to witness a 40- to 50-degree temperature swing! This dramatic “push/pull” diurnal cycle has a natural balancing effect on grape physiology, making Napa Valley one of the best places in the world to grow wine grapes.

The specialized geography at Hourglass Vineyard enhances this diurnal swing. The site’s position at the pinch of the valley helps draw in cool air, allowing the cooling effect to begin earlier in the day and the warming effect to begin later in the morning. Both work to shrink the vineyard’s growing degree days (heat over time) and to slow the front end of the ripening process, allowing the back end more time to catch up and achieve that magical balancing point. This delicate balancing act translates to slightly lower sugars (and therefore alcohols), slightly higher acids, deep phenolic concentration, and mature tannins in the wines. For this reason, Hourglass wines have always maintained a feline grace, with silky textures (due to bright acidity and polished tannins) balancing explosive aromas and deep flavors (from phenolic ripeness). All can be traced back to the vineyard’s unique geography.

Fractured Bedrock
The toe of fractured bedrock that juts out from the Mayacamas mountain where the Hourglass Vineyard sits is the result of massive volcanic activity more than a million years ago. It is an inhospitable place to grow anything but heartily rooted plants. The depleted, rocky Hambright soils here restrict a vine’s ability to grow by starving it of water and nutrients—one of the counterintuitive keys to farming world-class wine grapes. Its composition is a cobbled breakdown of fractured bedrock mixed with a thin patina of iron-laced soil. Modest clay concentration renders the soil poor in nutrients and causes it to be excessively well drained. When soil test pits were attempted at the site, the backhoe dug no deeper than 24 inches before being turned back by the stubborn rock below.

It has taken years for the root systems of the vines at Hourglass to become established. The stress from poor soil conditions inhibits the plants’ ability to size their berries in early spring, resulting in smaller grapes with high skin-to-juice ratios and wines of deep concentration. Similarly, the smaller leaf canopies that grow here indicate the plants have redirected their energy to focus on survival and developing their reproductive organs—their grapes—building deeper levels of polyphenols and more flavor in the process. Lifted earthy aromatics are also a result of the thin, intense soil series at Hourglass, which is generally found not on the valley floor, but in higher elevations where bedrock was pushed upward with tremendous force.

Just as a thumbprint is unique to an individual, so too is terroir unique to a great vineyard. Wind, rain, sun, and soil have defined the Hourglass Vineyard, which in turn defines its wines.