The Science of Vine Density

SEVENTYFIFTYDAILY

There’s no right way to space a vineyard, but winemakers and researchers nonetheless have strong—and often opposing—views on the best way to approach vine density

When establishing a vineyard, it’s nearly impossible to make a standalone decision. Every element, from the climate to the tractor, is part of a connected system. So when it comes to vine density—that is, how closely spaced vines are from one another—the ideal choice will largely depend on a suite of other factors.

At Chateau Montelena in Napa Valley, winemaker Matt Crafton has been working on two major replanting efforts over the past several years. In planning for these projects, every aspect of the vineyard and its management has been carefully considered in order to determine the ideal vine density. “It’s understanding the soil, understanding the climate, the right rootstock, right variety, right clone, right training method, right row orientation—all those things have to line up like a slot machine,” explains Crafton.

While it can be difficult to detangle a single element of a vineyard from the larger web, researchers and winemakers nonetheless have strong—and often contradictory—opinions on the best approach to vine density. Here, experts discuss the key ways in which vine density impacts wine quality and vineyard management in different regions around the world.

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Understanding Vine Density

Vine density, or planting density, is usually expressed as the number of vines per hectare or acre. Density is impacted by both between-vine spacing within a single row of vines, and between-row spacing within a given vineyard.   

Vine densities can range from hundreds to over 10,000 vines per hectare. The chosen density will be influenced by a range of environmental and socioeconomic factors and, in turn, the density will impact the style, quality, and price of the final wine.

Therefore, decisions on vine density will likely start by determining the type of wine a business aims to produce. “Your business goals should drive the decision-making,” says Stewart Spencer, the winemaker for St. Amant WIneryin Lodi, California, and the executive director of the Lodi Winegrape Commission. “Who is your customer? Or is it being developed for yourself?” These types of questions will help determine the quality and price of the final product, and how the winemaking operation will be financed and managed.

How Vine Density Impacts Wine Quality

Most winemakers aim to produce the highest quality wine possible for a given price. Therefore, most winemakers will choose a density that optimizes for quality. So, how exactly does vine density impact wine quality? Researchers and winemakers have tried to answer this question, though the results are not clear-cut. 

A common line of thinking states that high-density plantings increase grape quality by increasing competition among vines, which in turn decreases yield due to more limited access to resources. With fewer and smaller grapes being produced by each vine—creating a more favorable skin-to-juice ratio—the quality of each grape increases, resulting in better wine. But digging into the data reveals a more complex reality.

“A lot of this [thinking that] high density equals high quality is coming from unirrigated vineyards, and a lot of those vineyards are now reevaluating that idea,” says Mark Krasnow, Ph.D., a consultant and the owner of Thoughtful Viticulture in New Zealand. “The point of bringing them close together is to induce competition, but in a dry-farm situation or in poor soils, you can over-stress your vines and then you get poor growth.”

A study on an unirrigated Pinot Noir vineyard in South Africa, for example, found that the more densely planted vines benefited early in the season from less vigorous canopies, which allowed for greater sunlight penetration, but as competition for water increased later in the season, less dense spacing was more favorable for the vines.   

Many people also believe that increased competition among closely planted vines helps to drive roots deeper into the soil, further increasing the vitality of the vines. “When people talk about density, they say [higher density] drives the roots down,” says Dr. Krasnow. “My experience digging up vineyards shows that’s not true. Roots are very happy to intermingle with one another. But what you now have are two root systems colonizing the same soil, so they’re competing for the same resources. That’s where you get [lower vigor].”

There’s little research demonstrating that high-density plantings increase grape quality, though there is anecdotal evidence. At Shaw + Smith in Australia, for example, joint CEO David LeMire, MW, has seen promising results from their high-density vineyard in Adelaide Hills. “We went with 1.25 meters between rows and 0.75 meters between vines—10,666 vines per hectare,” says LeMire. “What we are seeing is lower yields per vine (as expected) and smaller bunches with smaller berry sizes. All of those are positive for skin-to-juice ratio and structure and intensity. It is too early for us to make claims, but we believe the quality benefits will be really significant—we’re not talking three or four percent, more like 30 to 40 percent.”

Other studies have shown a range of outcomes. A study on Chardonnay grapes, for example, showed that higher-density plantings led to lower acid levels in an irrigated site in Romania, while another study in Santorini, Greece, showed no meaningful differences in fruit quality between higher and lower planting densities on an unirrigated site. 

In sum, evidence shows that vine density does influence grape quality, but rarely in the same way for different vineyards. Therefore, it’s important to understand the myriad factors that contribute to a desired quality level for a given vine density. 

Environmental Factors that Impact Vine Density

Environmental factors will significantly impact the success of a chosen planting density. “It’s thinking about the wine you want to make and thinking backwards from there,” says Krasnow. “What environment do I want my grapes to grow up in? That’s thinking about the microclimate.”

For Crafton, it usually starts with the soil. “You have to understand the foundation before you move your way up into some of the more trendy topics,” he says. “And those foundational pieces of any vineyard are what’s going on below ground—geology and soil science.”

Soil is important because it’s a key factor in determining the water and nutrient supply for the vines. “Soil, water, and nutrition are often tied together because of soil texture,” says Krasnow. “Clay soils hold more water and they have more nutrient capacity. Sandy soils have less of both.” 

The levels of water and nutrients are important because they impact vine vigor, which in turn impacts vine balance and quality. “Wine quality is, to me, about the idea of vine balance, which is all about vigor management,” says Krasnow. “And density is essentially about vigor management.” However, research shows that controlling vigor may be achieved by either increasing or decreasing vine density depending on the other factors impacting the site, which has led to a range of different approaches. 

“Fertile soils in some areas—for example, lower Wairau Valley in Marlborough—can lead to high vine vigor,” says Ross Wise, MW, the viticulture innovation leader at Bragato Research Institute in New Zealand. “This could cause excessive shading, reduced airflow, and lead to potential fungal disease issues if not properly balanced. In this case, lower vine densities help to reduce vine vigor, as each vine is larger in size and has to work harder to support its increased vegetative growth and crop level.”

Krasnow sees a different approach to density when it comes to high vigor. “If you have a site that’s overbalanced towards leaf growth and you plant more vines, those vines slow each other down a little bit so the leaf growth isn’t as intense, and so that [the fruit] comes more into balance with the crop.”

When it comes to vigor, the grape variety, clone, rootstock, and trellising system also play a role, and further impact choices around density. Some varieties and clones are more vigorous than others, or have longer internodes, requiring more space. Similarly, rootstocks can significantly impact how vigorously a vine grows. And different trellising systems can create larger or smaller canopies, impacting space requirements and the amount of shade on the fruit.

Ultimately, it’s about understanding the right balance for the vine to create the desired style of wine, and learning how to farm for that outcome. 

Socioeconomic Factors that Impact Vine Density

For many wineries, however, quality will not be the sole, or even most important, factor in determining density. “If we were starting a winery and the only way we’re making money is cranking out 16 tons per acre in Modesto, that’s how we would set up our spacing—make it mechanically harvestable,” says Crafton. “The considerations change depending on the market, your brand, and your wines.” 

If a large winery aims to produce low-cost wines using fewer laborers, for example, mechanizing operations will be key, which in turn will impact the planting density of the site. “Choosing a row width that allows access by key vineyard equipment, such as machine harvesters, is essential, especially for larger vineyards,” says Wise. “Narrow row spacing can also lead to more technical work with machinery, which can require a higher level of skill or experience from the machinery operator.”

High planting densities also significantly impact upfront costs. At Shaw + Smith’s high-density vineyard, LeMire estimates the setup costs to be “around double what traditional Australian vine density would cost,” he says. 

Long-term management costs increase with high density as well. In Bordeaux, for example, which is known for high-density planting, “The tighter spacing and low height of the canopy make it harder to mechanize, and the sheer number of vines per surface leads to significantly increased labor costs,” says Axel Heinz, the CEO and managing director of Château Lascombes.

Land cost is also an important factor. During the replanting projects at Chateau Montelena, land-use efficiency was a major factor in determining vine density given the high cost of land in Napa. At a lower density, “We rarely were able to lay down canes long enough on each vine so that they were touching,” says Crafton. “We had some unused wire, which is just wasted space.” To increase efficiency, Crafton’s team replanted the vineyard at a higher density. “Essentially what we’re doing is we’re using our ground more effectively, which is really the holy grail.”

Planting Densities in Practice

There is no one-size-fits-all solution to vine density. With so many environmental factors contributing to a site’s terroir, plus countless economic and social factors to consider, every grower or winery will find a different solution to fit their specific needs. To help understand how the various possibilities play out, and what factors are top-of-mind for growers, it’s helpful to look at specific approaches to vine density in various regions around the world.

Marlborough, New Zealand

“Great wine can be made from both high- and low-density vineyards,” says Wise. “However, balancing vine vigor can impact wine quality and style, and vine vigor is influenced by vine density. For Marlborough Sauvignon Blanc, for example, a higher-vigor vine will lead to more leaves and more shading of fruit, which favors an intense herbaceous, methoxypyrazine-driven style of wine. A lower-vigor Sauvignon Blanc vine will have lower leaf density, leading to increased sun exposure to fruit. This in turn leads to a riper, more tropical, thiol-driven style of Sauvignon Blanc. Selecting a vine density to adjust vine balance either towards higher or lower vigor can help shape the wine’s style.”

Lodi, California

“Our vineyard was developed in the mid-1990s,” says Spencer. “At the time, the prevailing wisdom was to utilize a VSP [vertical shoot position] for producing the best quality. My dad chose an 8 by 10 foot spacing [8 feet between vines and 10 feet between rows], which is fairly low density, but part of that was driven by the equipment we had at the time. One of the challenges we face is the diversity of varieties and blocks. We grow nine varieties on 15 blocks across 43 acres. Each variety/rootstock combination performs differently. Tempranillo and Tinta Cão are very vigorous and Souzão is low vigor. We’ve made some modifications to the more vigorous varieties, like extending the height and adding cross arms. But one of the challenges is you need your equipment to work across the whole vineyard.”

South Australia

“At Lenswood, we are replanting to [a higher density of] 1.8 meters by 0.75 meters,” says LeMire. “Part of the idea is maximizing the quality and the potential of a site. Land, water, sunshine, energy—it’s all finite and by planting closer we’re maximizing the site, and that feels like a more sustainable model. We get more shade between the rows, so there is less evaporation, and we expect the vineyards will not need irrigation once the vines are mature. There are some people [in Australia] really embracing [high density] and others who are not convinced. New vineyards are rare, and new high-density ones are very rare, but there is a lot of curiosity about it. Australians are open to trying things, so there’ll be more.”

Napa, California

“For us here at Montelena, there were some very specific priorities on our estate vineyard,” says Crafton. “Number one, quality was through and through the most important thing. So we weren’t needing to triple our yields or something like that. If we’re able to increase our yields while maintaining quality, that’s great, but it’s secondary. The other piece is the long-term health of the vines. I look at that through a few different lenses, one of which is rootstock. There’s a piece of this that is pest and disease driven, but different rootstocks also impart different levels of vigor. So depending on what considerations you’re looking at from a pest and disease standpoint and how you choose your rootstock, the level of vigor that’s imparted into those vines will eventually drive some of the decision-making for vine density.”