Yield is one of the most-cited metrics in wine, but it’s also one of the most poorly understood. Whether expressed as tons per acre, or worse, as hectoliters per hectare, yield statistics are excessively reductionist in the absence of a host of other information. For wine quality and style, the most meaningful metrics are berry size (after all, the fruit of a grapevine is a berry, not a cluster) and yield per vine, figures which do tend positively to correlate with a wine’s depth and concentration—all things being equal.
But expressing yield as tons per acre tells us very little about berry size or yield per vine: a yield of three tons per acre looks very different, for example, at a density of 4,500 vines per acre or 1,600 vines per acre. Expressing yield as hectoliters per hectare (hl/ha), as is common in France, is even worse, as juice yields also vary between regions and varieties: in Burgundy, 145 kilograms of fruit typically produces one hectoliter of wine, but to produce one hectoliter of Napa Valley Cabernet requires around 175 kilograms of fruit (and juice yield will vary in every region from vintage to vintage). Producers create further confusion when they deduct fruit eliminated during sorting or must/wine discarded or declassified at the press from their quoted yields. From an agronomic perspective, the true yield is of course all the fruit produced by the vine, not simply the fruit that makes it into bottle.
These unsatisfactory methods of expressing yield are compounded by the assumption that, when it comes to yields, less is more. In fact, it’s balance that delivers excellence: a yield that’s adapted to the capacity of the site, the potential of the vintage to ripen fruit and the vigor of the vineyard as well as the inclination of the variety will deliver the best wines. Especially in high density plantings, exaggeratedly low yields are often indicative of missing vines, poor vine health and/or unsuccessful phytosanitary strategies (i.e., a lot of fruit lost to disease). Exaggeratedly low-yielding fruit that comes from stressed vines tends to lack nitrogen and micronutrients, entailing problems fermenting clean and dry. In Burgundy, for example, a vineyard planted at 10,000 vines per hectare without missing vines, producing three 100-gram bunches per vine—hardly an abundance of fruit—delivers a yield of 22 hectoliters per hectare. In reality, producing a yield appreciably lower than this implies that many vines are simply not producing at all; and this, it seems hard to contest, simply isn’t the objective of grape growing.
Pinot Noir vines in Romanée-Saint-Vivant in 2020 (left) and a high-quality Pinot Noir cluster
What are the main factors that influence a vineyard’s yield? The capacity of the soil itself is critical, in conjunction with planting density: higher planting densities produce more fruit per hectare without over-cropping individual vines, but not all sites can support higher densities. Graeme MacDonald’s 70-year-old Cabernet Sauvignon vines in the deep alluvial fan of the To Kalon Vineyard are planted at a low density of around 1,400 vines per hectare (10 feet by eight feet spacing), enabling them to be dry farmed during the dry Napa Valley summer. They typically deliver a punishingly low yield of around 12 hectoliters per hectare of dense, concentrated wine. Transpose those vines to Pauillac, without the hydric constraints of Napa, while increasing their density to the typical 10,000 vines per hectare of the top crus classés, and the same crop-load per vine would deliver a yield of more than 80 hectoliters per hectare with a consequent loss of quality.
Seventy-year-old Cabernet Sauvignon vines in Oakville, Napa Valley, cropped at one ton per acre (left) and their fruit (Photo courtesy of Graeme MacDonald)
Rootstock, variety and vine genetics are critical too. In Burgundy, the SO4 rootstock is capable of producing much larger crops than 161-49B. In Châteauneuf-du-Pape, vines planted on 3309C produce much smaller crops than those planted on 140RU. Irrespective of rootstock choice, some varieties naturally produce larger clusters than others: high-quality Pinot Noir is small, at around 100 grams per cluster; Cabernet Sauvignon is a little heavier, at around 125 grams per cluster; Grenache typically crops at around 200 grams per cluster; and Nebbiolo frequently attains double that. Within each variety, there is huge variation between larger- and smaller-clustered massal and clonal selections. And while smaller-berried selections are frequently superior, this is far from uniformly the case. All these nuances are ignored when yield is expressed in tons or hectoliters.
Old Grenache vines in Châteauneuf-du-Pape cropped at 35 hectoliters per hectare and their fruit (Photo courtesy of Julien Barrot)
Agronomic choices are also critically important. Pruning early tends to produce more abundant crops, but also results in bigger variation from year to year. Leaving longer or shorter canes or spurs delivers more or fewer clusters. Debudding and green harvesting also eliminate potential clusters. Other interventions influence berry size: soil management strategies shape a vine’s vigor by increasing or reducing competition; and canopy management strategies, in particular hedging/trimming during the season, also influence cluster size and morphology.
Then, the season itself comes into play: a vinifera grapevine flower contains four ovaries, and if all four are fertilized, the berry will contain four seeds, producing much larger berries than when fertilization is partial or unsuccessful (this is part of the explanation for the plethoric Pinot Noir crop in the Côte d’Or in the 2023 vintage). Fruit lost to frost, hail or disease also shapes the yield at harvest. And an abundance or absence of rainfall can change everything.
These nuances mean that assessing yield “by the numbers” is challenging. Even in a region planted to a single grape variety at a standard density, unavoidable differences in soil capacity, vineyard health, and the percentage of missing vines render direct comparisons difficult. When those factors are compounded by the presence of multiple cépages and differing planting densities, the exercise only diminishes in value. A move towards citing berry mass and yield-per-vine would offer armchair observers more meaningful data. In its absence, readers should allow some latitude when interpreting yield statistics.
