(Winemag) - Central Coast vintners who thought they were planting the “Monastrell clone” of Mourvèdre just learned that they were instead harvesting an obscure grape from Rioja.

On a recent afternoon in Paso Robles, Justin Smith, owner and winemaker, of Saxum Vineyards, stopped his truck alongside a sun-soaked flank of the James Berry Vineyard, the property founded by his parents that put this region on the global wine map.

“See the white tips?” he asks as he points toward a row of grapevines. “That’s Mourvèdre. But see the bronze tips? That’s Graciano.”

Those tips were one of the initial indications to Smith that the cuttings he bought in 2011 may not be Mourvèdre. The new vines grew much more vigorously, the fruit ripened earlier and when the grapes were harvested, the differences were even more striking. While Mourvèdre tends to show an earthy, animal character and can lose its acid quickly on the vine, these grapes were darker in color, brighter in fruit expression and full of acidity.