After phylloxera, Prohibition, and the Second World War, California wine was in a sorry state and needed reviving. There were a handful of growers and producers, especially in Napa Valley, determined to make quality wine and get California back on the map. There was also an influential wine writer called Frank Shoonmacker, who was frustrated by the insistence of many producers labeling their wines as "Chablis," "Sauternes," "Champagne," or "Burgundy" (which sadly still happens to a limited extent). Producers did this to make their wines seem more European and higher quality, neither of which was true.
So he came up with a novel idea: put the grape variety on the label, which was not practiced in Europe, as a means of distinguishing Californian from European wines and presenting a clear identity which had been lacking. It was an idea which Robert Mondavi, one of the pioneers of the modern California wine industry, enthusiastically took up. And it was extremely successful: now most consumers recognize different varieties and expect them to be on the label.
Producers in California are also helped by the fact that only 75% of the wine needs to be from that variety stated on the label (it's usually 85% elsewhere in the world, and 90% in Oregon), which is where the concepts of single-varietal wines and blends become murky. I’ve encountered many consumers in the US who say they don’t like blends even though the Cabernet Sauvignon they are enjoying is probably a blend of several different varieties.
Blends are useful for producers because they reduce costs by sourcing fruit from different vineyards or even regions. But blends can also add balance and complexity, as is the case with a Rhône style Grenache-Syrah-Mourvèdre blend.
Blends are part of the historic fabric of many wine regions. Back in the nineteenth century in California and elsewhere, farmers planted many different varieties in the same vineyard, which are now usually referred to as field blends. This may seem randomly chaotic—some old vineyards in California have up to 30 varieties planted—but the growers knew what they were doing. Planting and co-fermenting Zinfandel, Petite Sirah, Carignan, Alicante Bouschet, and Mourvèdre together, for example, produces a wine in which the grape varieties complement each other and add to the complexity of the wine.
Nineteenth-century growers in California did this because they were European immigrants used to the practice of field blends in countries like Italy. It’s still also common in Portugal (one of the reasons Port cannot be made from one variety), and blackpoolmatt’s wine club has just got in a wine from Alentejo, a warm region between Lisbon and Spain. This historically was a poor region where growers would plant anything local they could get their hands on. There wasn’t an emphasis on one single variety; instead, many varieties were planted which were known to be suitable to the warm, dry growing conditions.
"Sempar” is a red wine from Dirk Niepoort, a legendary producer whose innovation is based on past traditions, and it takes the lack of varietal labelling to a new degree. There is no information on the grape varieties used, other than it is a field blend, placing an emphasis on where the wine comes from rather than what it’s made from. A problem the Portuguese wine industry faces is that there are so many indigenous grape varieties (around 250) that it's hard to sell the wines to consumers who have never heard of them. But instead Portuguese producers can promote their wines through regionality and the history of the vineyards.
The problem with labeling and marketing a wine with a single grape variety is that it becomes about the grape; a field blend is what a wine should be about: a sense of place. It's not necessary to focus on the grape variety, but where the wine comes from. Which, ironically, California producers have begun to embrace as producers in regions as diverse as Napa Valley and Sta Rita Hills market the wines on where they come from rather than solely the grape variety. What comes around goes around.