Zinfandel

Zinfandel's identity was one of the great puzzles of ampelography, and it took DNA analysis to solve it. It arrived in the United States in the 1820s as a table grape and became California's signature variety, but nobody knew where it came from. In 1994 it was matched to Italy's Primitivo, and in 2001 researchers traced both to a nearly extinct Croatian variety, Crljenak Kaštelanski, now generally called Tribidrag.

In California it makes a wine of considerable power: blackberry, black cherry, raspberry jam and dried fig, with black pepper, liquorice and sweet spice, high alcohol — fifteen or sixteen per cent is common — and soft, generous tannins.

The grape's defining difficulty is uneven ripening. Berries within a single bunch reach maturity at different rates, so any harvest contains a mixture of underripe fruit, perfect fruit, and raisins. That raisining is the source of both the jammy, port-like character of the riper styles and the high alcohol.

The most valuable material is old vines. Plantings in Sonoma's Dry Creek Valley, Contra Costa and Lodi date to the nineteenth century, many of them head-trained, dry-farmed and on their own roots, and they produce concentrated, complex wine quite unlike the commodity version.

Many of those vineyards are field blends, interplanted with Carignan, Petite Sirah and Mataro by immigrant growers who planted for insurance rather than varietal purity.

Its survival through the late twentieth century owes a good deal to the commercial success of White Zinfandel.

The uneven ripening is the central practical fact about the grape, and it dictates picking strategy. Wait for the green berries and the wine will contain a large proportion of raisins, giving high alcohol and a jammy, port-like character. Pick earlier and the wine is fresher but carries an unripe edge. Most producers accept some raisining as the price of ripeness, which is why fifteen per cent alcohol is normal.

Old-vine Zinfandel is a genuine category rather than marketing. Vines planted between 1880 and 1920 are still producing in Sonoma, Contra Costa, Amador and Lodi, head-trained and dry-farmed, and they yield perhaps a third of what a modern trellised vineyard does. The concentration and balance of those wines is not reproducible by any other means.

The field-blend tradition is worth seeking out: old vineyards interplanted with Petite Sirah, Carignan and Mataro, picked and fermented together, which adds acidity and structure the Zinfandel alone lacks.