Stag’s Leap Wine Cellars
Rootstock and Clones in the Vineyard
When speaking of vines and vineyards, the conversation eventually makes its way to the subject of rootstock and clones. Both can contribute to the quality of the grapes the vineyard produces. To understand these terms the best place to start is with the grape vine.
While a number of species of grapes grow wild across the globe, the vines that produce wine and table grapes come almost exclusively from a single species –Vitis vinifera. The different varieties – both red and white – are the result of genetic variations that were selected and preserved over thousands of years. Historical evidence shows the grape vine was one of the first plants to be domesticated in the areas of Georgia, Iran and Turkey as far back as 8000 years ago. The vine’s ancestor was a wild grape called Vitis sylvestris that still grows wild in Europe and Asia today.
Grape vines can grow from seed, but the offspring of the seed will not produce a grape with the same characteristics as the parent vine. This genetic diversity gives the wild grape an advantage over pests and plant diseases, but means desirable flavor, aroma and color characteristics may be lost from generation to generation. In contrast, the vine is easily reproduced through propagation. The trailing end of an existing vine buried in the dirt will root and become a second vine with fruit identical to the original. The vines are hardy and can be transported to new locations and replanted. It’s easy to imagine how our ancestors might have made the leap from gathering the tastiest Vitis sylvestris grapes from the same locations year after year, to propagating more of the vines with the best fruit. This led to the creation of the first vineyards. These basic methods of selection and propagation became the basis for the cultivated varieties that we use to create wine today. Domesticated grape varieties and wine production spread outward from the ancient Mesopotamia region reaching deeper into Eurasia, Northern Africa and Europe. Grape vine cultivation continued like this for centuries.
In the 1800s, vines from Europe were transported to the New World, creating vineyards full of Vitis vinifera varieties in the Americas where they had never grown before. Other Vitis species that grew wild in the New World–labrusca (Scuppernong) and rotundifolia (Muscadine) for example–made their way to Europe for experimentation. It was through this exchange of plants that disaster struck the wine industry. Phylloxera – a tiny root-eating louse- which was native to America was unintentionally transported to Europe. And, of course, plant diseases which plagued European vineyards made their way here as part of the exchange.
Phylloxera decimated the vinifera grape vines in both California and Europe. It is estimated that more than two thirds of all European vineyards were destroyed between 1863 and 1889 by the pest. A group consisting of two European scientists and an American horticulturist from Texas developed a method that grafted the vinifera vine onto the Phylloxera resistant roots of grape species native to America. This simple procedure saved the wine industry and marked the beginning of a scientific approach to grape vine propagation.
Most modern rootstock comes from several different varieties and variations that are recommended depending on local pests, soil and weather conditions. The grape bearing (vinifera) part of the plant, known as a “scion” is grafted onto the vine that grows from the roots. Stag’s Leap Wine Cellars uses a cross of riparia and rupestris, designated as 101-14. Chosen for its ability to resist Phylloxera, it is the most commonly used rootstock.
The history of the grape vine clone is a story all its own. A clone is a “genetically uniform group that derived from a single individual by asexual propagation.” While it sounds futuristic, cloning grapes started with the traditional propagation methods such as using cuttings or by rooting new vines from existing plants. Historically, a well established vineyard, in Bordeaux for example, might contain sections devoted to cabernet sauvignon, but it wasn’t uncommon to find other grape varieties mixed in the rows. And even when the varieties were the same, groups of vines created through traditional propagation had minor genetic variations that created subtle differences in flavors and aromas.
Along with the variations found in the old European vineyards, there are 10,000 common names for grape varieties. The research that started with the spread of Phylloxera began to untangle the massive jumble of common names and local lore. Scientists identified approximately 500 unique varieties and discovered previously unknown genetic relationships. For example we now know cabernet franc and sauvignon blanc are the genetic parents of our favorite grape at Stag’s Leap Wine Cellars – cabernet sauvignon. Thought to be a random genetic crossing that can be traced to the 17th century in France, cabernet sauvignon quickly gained popularity with vintners. The vines grew well and the fruit produced a tasty wine.
Each of the major grape varietals now has a subset of propagated choices. When you plant a vineyard, be it with cabernet or chardonnay, there are dozens of official cultivated variations that produce a range of different flavors for a variety. Some vineyards and wines may be created from a single clone.
Stag’s Leap Wine Cellars prefers the traditional planting style for the estate. Modeled after the diversity found in old Bordeaux vineyards, we grow a mix of clones. This provides the wine making team with a painter’s palette of flavors and aromas to create the complexity you taste in the wine. It’s all a matter of style and taste combined with science and history in the vineyard.
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