Tel Button

Why do Clones Matter?

by David on June 30, 2009

Geoff in the vineyardWe always start our tours out in the vineyard, at Goosecross, and we quite often mention that Geoff Gorsuch, our Winemaker, has our nine and a half acre estate vineyard divided into 11 different sections. This is a Cabernet-dominated vineyard, but since we grow 3 other Bordeaux varieties on the property, there’s an obvious division into four and then I explain that the other sections are due to differences in spacing, rootstock, hybrid and clone. Almost inevitably the next question is “what the heck is a clone?”

The word clone tends to bring to mind clinical images of Petri dishes and labs and all the ethical questions that came up with the advent of Dolly the sheep. But, when it comes to grapes, new clones are purely an act of nature and the science involved is in studying them and learning how to identify them accurately.

What is a clone?

First of all, what’s a clone? Evidently, everything that grows, including us humans, is subject to natural and spontaneous genetic change, which we call mutation, another kind of scary term. But, mutation is just part of nature. The defines it as “A change of the DNA sequence within a gene or chromosome of an organism resulting in the creation of a new character or trait not found in the parental type.”

As more time passes, the potential for mutation increases. For instance, Pinot Noir is a very old wine grape and clonal selection is a topic of intense interest and discussion among winemakers. Cabernet Sauvignon has only been around since the late 1700s and, though there are various clones available, clonal selection doesn’t generate nearly as much debate. We also know that some varieties, like Pinot Noir, tend to mutate more easily than others. What it means is that if you have a very old Pinot Noir vineyard, it could be that you have a few different versions of the variety growing out there by now. You’d have to study the individual vines very closely to know.

So, we know that there are variations within a number of varieties available. Our job is to figure out which versions we prefer and replicate them. This is where it starts to become scientific, which is just a matter of people paying very close attention.

This has been done on a comparatively casual basis throughout history, meaning that the grower would notice that some of the vines in his acreage performed better than others and he would take cuttings from those preferred vines to propagate new ones.


Let’s take a brief look at propagation. Every grape variety, such as Chardonnay, originally came from a single plant. Sometime very long ago, someone liked this original Chardonnay and decided to propagate it. Assuming this person knew what he was doing, he propagated that Chardonnay by cutting, not by seed. As you know, seeds are created by the pollen fertilizing the ovule which means the parents of the seed are 2 different beings. When they join, they produce a new plant with a new set of genes. This is the right approach for breeding new grape varieties, but for the purpose of replication, it doesn’t work.

So the work has to be done by cutting or bud. The buds on the cutting have all the genetic information needed to reproduce that clone. When you hear the term “bud-wood” it just refers to the buds from the cuttings. Formalization and subsequent certification of clonal selections didn’t come about until the 20th century, first in Germany, in1926, on a voluntary basis which was later signed into law, and then France in the 1940s. These days nearly every wine-producing country has some kind of governmental organization for identifying clones and rootstock and certifying them as virus-free. Here in California, the program is conducted by the Foundation Plant Services at the University of California at Davis.

Identifying and replicating clones

We’ll use the French model to describe the very laborious process. Initially, just like that old-time farmer, government-funded scientists isolate individual vines of interest for any number of reasons such as good crop production, disease resistance, early ripening or distinctive fragrance or flavor. In the early days of clone identification, the first priority was vine health, next was consistent productivity, and last was wine quality. These days we can’t forget the first two factors, but wine quality and character has moved to the fore.

They take some buds of each clone and then plant them in a small trial. It’s important to grow different clones side-by-side to be sure that the characteristics being monitored aren’t due to the site rather than the clone. They grow these vines until they’re old enough to be harvested and make wine from them for several years. Gradually, the less interesting vines are winnowed out and the survivors go on to bigger trials, covering more area. These trials are conducted over a number of years. The attributes of the clones need to be consistent all that time and after about 15 or so years of these trials the most interesting or successful clones are assigned a number. They’re set aside as “mother stock”, and are used for future propagation. Given that the mother stock can mutate and the possibility of the spread of virus, these scientists have to be ever vigilant. At some point they may find that they have clones of clones.

Field Selections

When you hear the name of a California clone instead of a number, like the Swan clone of Pinot Noir, the process is usually more similar to that old farmer’s approach than formal cloning. Say farmer Jane admires the Pinot Noir from Swan Vineyard in Sonoma and gets permission to take bud-wood in order to plant the same clone. And then farmer John gets bud-wood from farmer Jane, also calling it the Swan clone, and so on. Purists prefer to call this a field selection, instead of a clone, because it’s obviously not very carefully controlled. It doesn’t mean it isn’t a good process or selection; it’s just more of an unknown because it can’t be traced to the mother vine.

Mass selection

The term mass selection is very similar and is usually done for the sake of diversity. A field selection of bud-wood from many vines is purposely selected and intermingled in the vineyard instead of using clones that come from a single mother vine. The upside is a potential for greater complexity as each different clone and, possibly even different variety, makes its own flavor and aroma contribution. The downside is that there may be vines included with undesirable characteristics whether they are of poor yield or fruit character.

Proprietary clones

There are individual wineries and growers doing their own work in clonal selection. Some of the best Bordeaux houses do their own clonal selection from the vines on their property, which perhaps means they become proprietary clones. In the early 1950s, here in Napa Valley, Louis Martini showed great foresight by taking a large number of clones from the Stony Hill vineyard for in-house clonal trials. He also shared his cuttings with the University of California at Davis so they could do a more formal study. Francis Mahoney is famous here in Napa Valley for his Pinot Noir clonal trials in the early 70s, as then proprietor of Carneros Creek Winery. By now, it’s almost de rigueur for the top producers of Pinot Noir to conduct their own clonal research.

“Suitcase clones”

The phrase “suitcase clone” refers to cuttings taken by those who want the bud-wood of a particular vineyard in another region, and don’t want to wait until its quarantined and certified in their country or state. With or without permission, cuttings are taken from the vineyard and they, literally, come home in a suitcase. Al Brounstein openly admitted that he smuggled cuttings from each of the five first growths of Bordeaux to start Diamond Creek Vineyards here in the Napa Valley. He must have divulged this after the statute of limitations had run out. In the US, it’s not legal to import foreign plant material unless it goes through California’s plant quarantine system for inspection and to eliminate any trace of disease. Then vines are then propagated in a controlled environment. The problem is that it can take up to six years, sometimes even longer. Violators risk a hefty fine and possibly even jail-time, but the practice isn’t unheard of, especially among those passionate producers who are determined to make the definitive Pinot Noir.

There’s been a side benefit to all of this study. With the introduction of grafting in the 1880s, due to phylloxera, a number of viruses were inadvertently spread. The unacceptably high percentage of infected plant material in the 20th century was what led to the formation of these organizations to study and certify the clones. As recently as the 1960s it wasn’t uncommon for vineyards in Europe and the new world to contain misidentified varieties and virused vines. The advent of formalized cloning helped to clean up the plant material and by now many nurseries will only propagate from clonally selected rootstocks and varietals. Disease and virus will always be with us, but at least we have the advantage of starting with virus free, properly identified plant material.

Now that we’re gaining a somewhat better understanding of clones and selections, if there’s a downside, it’s expressed as a one-size-fits-all sort of trendiness. Matt Kramer of the Wine Spectator recently expressed frustration that so many new-world Pinot Noir producers, and some in Burgundy, are so fixed on using a handful of Dijon clones currently in vogue that the wines are starting to taste the same. The most popular clones, at present, tend to produce extractive, powerful wines. It appears to some that it’s become routine to blend the big red-cherry flavor from Dijon clones 113 thru 115 with the heavy black fruit of clone 667. We’re on a steep learning curve and it will take some time for each producer to find the right mix of clones that are suited to their individual terroir and have distinctive flavor and aroma contributions to make.

Matching the clone to the site

It’s important not to isolate the clone, no matter how popular, from the site. A clone that performs well in one place may not be as well suited to another. For instance, some of the characteristics that are seen as attributes in France, such as early-maturing or low-acid clones, might be viewed as liabilities here. Those are great qualities for a region that errs on the cold side, but not for a warm region like Napa Valley. We have to careful to match the clone to the site.

That was part of Geoff’s game plan when he was getting ready to replant our estate vineyard, here in Yountville, a few years ago. He worked with a couple of the best local viticultural consultants to help re-assess the property. They re-checked the meso-climate and dug deep soil pits in various parts of the property so they could see which areas are more or less vigorous. Then, they talked with our supplier about the available clones, their suitability to our situation and chose the rootstock hybrids and clones accordingly. Geoff also selected them for their differing sensory characteristics. Cabernet clones may not be the hot topic that Pinot Noir clones are, but he wants to see how each of the 3 clones he selected performs on our site and how they differ in wine character. Plus, there’s the opportunity for added complexity that each clone can bring to the total blend. Most winemakers would likely agree that if they’re planning to produce any amount of a certain variety, it’s smart to plant a few different clones and take advantage of what each has to offer. For instance, clone 337 Cabernet Sauvignon offers great concentration and classic Cabernet character, but clone 169 offers beautiful aromatics and is more drought tolerant. For the same reason he planted a few clones each of the Merlot and Cabernet Franc.

Clonal selection is only one of so many puzzle pieces in this complex subject of growing and producing fine wine. The fact that the subject is endless is what makes it fascinating. Grape juice and yeast make wine. Beyond that there are countless subjective choices to make whether they are of clone, irrigation decisions, determining grape maturity, using cultured yeast vs. wild fermentation, choice of barrel – it goes on and on. And, as we’ve said so many times before, the fact that we’re a relatively young wine producing region here in the Napa Valley means that, as good as the wines are now, they can only get better as we learn more.

Previous post:

Next post: