In May, vineyard managers turn their attention to replanting vineyards that have outlived their usefulness for reasons of age, disease or the fall from grace of their varietals. While the Kunde crew bulldozes these underperformers, Old Vine Zinfandels are left alone to do what they do best. Our elderly plant sprouts buds from nooks and crannies that seem all but dead. They unfurl into spiky leaves, each a work of art. Just days later, nubby little shoots push past the foliage. At the end are tight clusters of blossoms, each of which can theoretically become a grape.