Zinfandel

Zinfandel, Italian primitivo and Croatian tribidrag are one grape. The link was established by DNA work at the University of California between 1994 and 2001, which traced the American vine back through Puglia to a nearly extinct variety on the Dalmatian coast, where fewer than two dozen plants were found. It reached the United States through a Long Island nursery in the 1820s and travelled to California with the Gold Rush.

It ripens unevenly, and that single fact shapes the wine. A single bunch can hold raisined berries and green ones at the same time, so the winemaker chooses which to favour. Picked to catch the ripe fruit, it makes a high-alcohol, jammy, brambly red with sweet spice, often 15 to 16 percent. Picked earlier it is brighter and more peppery but risks green edges.

California's old zinfandel vineyards, many planted before 1920 in Sonoma, Lodi, Amador and Contra Costa, are among the country's real assets: dry-farmed, head-trained, low-yielding and often interplanted with petite sirah and carignan as field blends. Puglia makes primitivo in a warmer, softer style. And the pale sweet wine called white zinfandel, invented by accident in 1975, still sells more volume than the red does.