Yield versus Quality, Part 3

Crop Thinning & Overcropping

When a vine is carrying more fruit than it is able to ripen, it is overcropped. Green harvesting or crop thinning is the removal of excess grape clusters to insure that those remaining clusters will fully ripen. Chris Howell, Cain Cellars Winemaker discusses overcropping, “Anyone who works in vineyards is familiar with situations where the vine is visibly overcropped—there are all these grapes hanging out there and you don’t see that many leaves. The fruit is never going to have any intensity.”

Growers usually err on the side of leaving more crop on the vine. If excess crop is realized through good fruitfulness, flowering and set, it can be reduced so that the vine is carrying a crop it can ripen before fall weather patterns set in. Christian Moueix, who started crop thinning at Chateau Petrus in 1973 comments, “We need to crop thin in Bordeaux. Of course, when we crop thin usually in July we don’t know what the weather will be like in August and September. We have a feeling, we have a weather pattern, I will say, by that time and we adapt the level of crop thinning to the feeling of the vintage. If we are in a rainy year, we crop thin more severely, if we are in a hot year we crop thin a little less severely.”

Paul Pontallier, Technical Director at Chateau Margaux explains that crop thinning in Bordeaux is a more recent practice, “We at Margaux were the first to crop thin in the Medoc and that was in 1986. We had the experience of Petrus doing it for a few years. We try to keep our yield reasonably low because we never know if the conditions are going to be good or not.” Jean-Michel Cazes discusses his yield guidelines at Lynch Bages: “We try to get 50h/h. We look at the parcels before the harvest and when we see that yields might go over that limit, we discard the excess grapes. We try to green harvest at the time when the grapes become red (veraison) so that we can see which clusters are riper than others and get rid of the ones which are still green.”

Bruno Prats from Chateau Cos D’Estournel practices green harvesting only on young vines, “While their vigor is a little too strong,” he says. “It is a substitute when you have vines which are too vigorous and you want to artificially reduce the yield. It’s like pushing the gas pedal and the brake at the same time. It’s better not to use the brake and put in a little less gas.” He adds that to really achieve quality, “You must have a naturally low yield. We don’t have to do it on the old vines which normally produce low yields.”

In California, Ridge’s high altitude Monte Bello vineyard is faced with such potentially harsh spring weather that thinning is mandatory. Winemaker Paul Draper explains, “During flowering and set in at least one year out of three, the weather is so difficult that we must start with more buds and plan to thin if nature does not thin for us. If not, yields can often fall below one and a half tons/acre (20h/h) and adversely affect quality. In 1997, with good spring weather and a huge set, we dropped 30% of the crop and ended up with 3 tons/acre (40h/h) and a superb vintage. We are quite traditional in vineyard and winery practice, however, we feel that balancing the crop to the vine and to the conditions of the vintage is an essential part of the role of the vintner as guide rather than maker.”

The experience of David Gates, Ridge’s Vineyard Manager provides a compelling argument for drastic crop thinning and how it can be variety specific. Since younger vine Zinfandel tends to produce larger berries, carrying excess clusters causes the individual berries to remain small. The excess clusters are thinned at veraison. The remaining fruit goes into Ridge’s vineyard designate Zinfandels.

In Burgundy, green harvesting is not a standard practice. While Domaine Dujac has practiced it since 1989 at veraison, Domaine Roumier, Domaine Grivot and Comtes de Lafon crop thin only occasionally. Christophe Roumier comments, “I green harvested in ‘96, the last time before was in the young vines in ‘92 and before that in ‘86. Only in the young vines because the old vines don’t need it. The people who are green harvesting every year have young vines and they have no choice if they want to keep their quality.” Etienne Grivot states, “I don’t like to make a green harvest. If you have to put off a proportion of the green grapes, you have to understand why the quantity is too big. If you cut off 20% green grapes, you don’t obtain 20% less juice, just maybe 10%. So it means that you have less skin and more juice and you obtain the opposite—a kind of dilution. If the vineyard is too vigorous, it is normal to obtain too much fruit.”

Green harvesting is a controversial issue not only as to whether it should be done, but when it should be done and whether or not, as Grivot alludes to, the grapevine compensates for fewer clusters by producing larger berries. Dr. Nick Dokoozlian, Viticulturalist in the UC Davis Department of Viticulture and Enology says compensation does not occur if you thin at veraison at which point berry enlargement is over, “Thinning at veraison does not normally show the data Grivot is showing. You don’t affect the crop based on berry size. If you thin at veraison, it is too late for the vine to compensate through berry size. If you thin too early you will get compensation because the berries are still growing in size.” But thinning at veraison is still an imperfect solution since the discarded cluster represents a waste of the vine’s energy.

Lafon’s views are more strident, “When I hear people talk about green harvest it makes me laugh. It’s so stupid to me—it’s just like saying to everybody that they have selected the wrong rootstock, the wrong clone, they have used too much fertilizer and that maybe they have the wrong pruning, so they have too much crop. It’s just that they have accumulated too many mistakes all the way through, and the only thing you can do is green harvest. I see it here, a lot of my customers say, ‘you must be doing green harvest’, I don’t. If I have to do it, I start to think and get back to viticulture to avoid it. You might have one small mistake in one vineyard, but if all your vineyards are like this, you are really doing things wrong. And I think you also have to accept that some vintages are more generous than others and if you have done everything right from the start, then you can take a bigger crop and make very good wines.”

Lafon’s outlook may seem idealistic to some growers in California who rely on crop thinning to compensate for the fact that rootstock and clone are not correctly matched to the site. Vineyards were originally planted according to research done at Davis funded by large wineries to develop the Central Valley. At that time, the mindset for low yields wasn’t there. AxR1 was chosen because it was easy to grow and graft typically onto high yielding clones. Francis Mahoney owner of Carneros Creek Winery cites an example, “You don’t want to put on a high-yielding clone on ground that is very shallow. Because in the springtime when there is plenty of moisture and sunshine, you’re going to set a big crop but the ground won’t be able to bring it along. So you end up with this, ‘let’s go drop the crop.’”

Lafon says that green harvesting is looked upon by some growers as an insurance policy: “A lot of people, when they prepare and work the vineyard, regard green harvest as good insurance. You put 80-90h/h every year on your vineyards. You crop thin to 50h/h for example, and every year you are sure that you will make 50h/h. If you do everything right to have 50h/h, then if there is frost or bad flowering, then you might go down to 25h/h. There are a lot of growers who just won’t accept that. It’s a question of money, when you lose half the crop at flowering, it’s not fun in a financial way. Some of my vineyards move from 20h/h to 50h/h, and for whites I take 50h/h when it all goes well and I am not going to crop thin. For reds the maximum we will gather is 40h/h.”

Although there is a lack of consensus regarding crop thinning, there is agreement that overcropping dilutes flavor intensity. The consequences extend to the following year—the excess crop exhausts the vine by depleting its stored energy reserves causing sluggish growth the following spring leading to reduced fruitfulness, excessive vegetative growth, shading of clusters and delayed maturity. But there is no exact point when overcropping begins. “I don’t think that there is anyone, anywhere who denies the fact that if you overcrop a vine it will affect wine quality,” remarks Steve Hill who farms 250 acres of Sonoma’s Durrell Ranch. He adds, “The question is, where does overcropping begin? At what point do you begin to affect wine quality”. Nonetheless, the temptation is strong in California to hang extra crop due to grape shortages resulting from two successive short crops (’95 and ’96), replantings due to phylloxera and the sustained high demand for top quality California wine. The late Justin Meyer, former winemaker at Silver Oak Cellars commented, “A lot of people are pushing their vines hard now because it’s a high demand, high price time and they figure that now is the time to get rich. And you can push them over the edge. I don’t care if you have twice as much if it’s half as attractive.”

Since the grape business has turned into a seller’s market, some California winemakers who buy grapes on the open market are protecting themselves against the potential for overcropping by entering into acreage contracts. Let’s say Cabernet Sauvignon costs $2,000/ton from a vineyard which the grower usually produces 5 tons/acre. The winemaker will pay the grower $10,000/acre and instruct the grower to limit yields to whatever crop level the winemaker feels is necessary to produce the best wine. California’s first acreage contract was in 1993 when Ted Lemon of Littorai Winery produced a vineyard designated Pinot Noir called “One Acre.” Lemon explains his motivation, “I wanted to underline that yield containment was the future, not only for California but especially Anderson Valley Pinot, whose soils can support yields of 4-5 tons/acre; that the diluted, simple that had come out of Anderson Valley resulted from a lack of viticultural input.”

Pontallier comments as to whether overcropping exists in Bordeaux, “In Bordeaux, our Appellation Controllee system has fixed limits for production because we know from very, very old experience that overcropping is bad for quality—even if the level of the crop is not easy to fix. But in order to protect the quality of our winegrowing areas, we have for each, limits of yield. In other winegrowing areas where there is no limitation, people have a natural tendency—if they have a good market—to produce more wine, which we cannot do.”

In Burgundy, the incentive to overproduce has always existed due to the historically high demand for limited quantities of wine. Unfortunately, of all grapes, Pinot Noir suffers most from overproduction in a climate where the penalties are so severe. Jacques Seysses comments, “There was a period where Burgundy overcropped, no doubt. One should remember that in the ‘50s, a grower in Burgundy was having a hard time making a living with his production. So the trend at that time was to replant a selection that would produce more so that they could live better. That selection didn’t lead to quality. As these vines got older they made better wine, but it is not the same as if the selection was good in the beginning.”

Conversely, an undercropped vine will have equally detrimental effects on quality. Cain’s Howell, comments, “Where there is a big jungle of foliage and you don’t see the fruit, the little bit of fruit that is buried in that foliage is going to taste like vegetables.” When a vine is in balance, further reducing yields may decrease quality, according to Tom Rochioli, “Last year (1996) yields were off 40% so the vines were out of balance. We pulled leaves and opened up the canopy to expose the fruit. Nonetheless, the ‘96 wines had a slight herbal edge. The wines were not bad, but I went to the edge of where I wanted to be with regard to these flavors.” Herbal or vegetal flavors such as asparagus or bell pepper come from sunlight sensitive compounds called pyrazines and are extracted from the skin of Cabernet, Merlot, Cabernet Franc and Sauvignon Blanc during fermentation. High levels of pyrazines are found in fruit that has been shaded by excessive foliage. Growers pull leaves and position shoots to improve the light environment around the clusters. A high leaf to fruit ratio while good for ripening, is bad for the veggies.

Somewhere between overcropping and undercropping as Rochioli alluded to, the vine is in balance, a balance between foliage (canopy, leaf surface area, shoot length) and the number of clusters. This balance creates more fruit in some sites and less fruit in other sites, meaning that yield cannot be talked about without discussing a specific growing region and site.