It was a hot day in the vineyard, and I was covered in dust, sweat and sticky juice from the grapes I had been collecting for my research on how grape biochemistry is affected by light and temperature. Suddenly, I saw something that made me stop short. Tucked in one corner of this 6.5-acre plot in Carneros, in California's fabled Sonoma Valley, with row after neat row of Pinot Noir grapes, were a handful of alien vines. I had studied the arcane art of ampelography—the practice of identifying grapevines by the shape of their leaves and clusters, as part of my graduate training in viticulture—so I took an educated guess at what they were: the red varieties Cabernet Franc, Petit Verdot, Syrah and Malbec, plus a white, Sauvignon Blanc.