The Titus Vineyards sits in what Eric Titus calls the “choke-point” of the Napa Valley. The precise spot of his 38-acre parcel is located at the narrowest part of the 30-mile long valley. If the Valley were an hourglass, the Titus plot would be at the pinch in the middle.

As in the case of wine grapes, the choke point in the Napa Valley, at Titus’ vineyard, is where all of the region’s historical geologic roiling has deposited its volcanic detritus. That’s significant because it seems, through all of the millennia of the valley’s earthly life, what defines the area’s lifeblood – growing grapes – wound up on Titus’ site. And this confluence of terroirs informs us what winds up in the bottle.

When first asked about those soil types, the 47-year-old Titus, who runs the vineyard, said simply that he doesn’t know. But the next 115 minutes, sitting in the small clapboard house on the Silverado Trail north of St. Helena and exactly “six telephone poles” past Deer Park Road, are virtually filled with a detailed delineation of Titus’ parcel.

The home ranch vineyard has 14 ½ acres of Cabernet Sauvignon, 8 ½ acres of Zinfandel, 2 acres each of Malbec, Petit Verdot and Cabernet Franc, 2 ½ acres of Petite Sirah, and 2 acres of Sauvignon Blanc. The later variety will first be released with this year’s harvest. Titus also owns 6 ½ acres of Cabernet on Ehlers Lane, a few miles northwest of the estate. His brother Phillip, 50, makes the wine for the family’s eponymous brand.