Rootstock in Viticulture: The Invisible Decision That Influences Decades

Key question: why is the part of the plant that no one sees one of the most decisive choices in a wine business project?

In Chapter 1 of this series, we introduced the five elements of terroir, based on the scientific approaches of researcher Claudio Pastenes, professor at the University of Chile: climate, soil, water, plant, and human factor. We explained there that the plant, the fourth element, brings together three distinct decisions: variety, clone, and rootstock. In Chapter 2, we explored the first of these decisions in depth: variety.

This chapter deals with the second decision, the rootstock, probably the most invisible one in the entire series. Unlike variety, which appears on the bottle's label, the rootstock is literally underground. But it is what sustains the plant for decades, and for that reason it may be the most silent and most decisive choice in the whole project.

While most conversations about wine revolve around grape variety, terroir, and winemaking technique, almost no one asks about the rootstock used. And yet, it is the rootstock that decides whether the chosen variety will survive in the chosen soil for the decades ahead.

1. Resistance: the historical origin of the rootstock

In the late 19th century, phylloxera, an insect of North American origin that attacks grapevine roots, destroyed a large part of Europe's vineyards. The solution found was to graft Vitis vinifera, which is susceptible to the pest, onto rootstocks from naturally resistant American species, such as Vitis riparia, Vitis rupestris, and Vitis berlandieri. Since then, the vast majority of commercial vineyards worldwide have been grafted; own-rooted vineyards (ungrafted) survive today only in predominantly sandy soils or in isolated regions where phylloxera cannot establish itself.

Beyond phylloxera, different rootstocks also vary in their resistance to nematodes and other soil pests, a criterion that can matter a great deal depending on the area's land-use history, especially in land where a vineyard or another susceptible crop has already existed.

2. Vigor: controlling the plant's growth

The rootstock also controls the plant's vigor, that is, how much it invests in vegetative growth. More vigorous rootstocks push the plant to produce more leaves and shoots, which can be desirable in poor soils, where they help the plant establish itself, but detrimental in already fertile soils, where excess vigor dilutes fruit concentration and compromises wine quality. Moderate-to-low vigor rootstocks, on the other hand, help contain that growth and favor concentration, making them the most common choice in projects aimed at high-quality wines.

This vigor control also connects with future decisions in this series: a vigorous rootstock, for example, increases the canopy management workload, a topic we will cover in Chapter 7, to avoid excessive shading and sanitary problems.

3. Soil adaptation

Each rootstock has its own profile of tolerance to the soil's physical and chemical conditions: some cope better with calcareous soils, which cause an iron deficiency known as lime-induced chlorosis in sensitive rootstocks; others tolerate drought, waterlogging, salinity, or heavier clay or sandy soils better. This adaptation directly revisits the soil and water analysis from Chapter 1: the same rootstock that is the right choice on one plot can be the wrong choice on the plot next door.

4. Productivity and longevity

Finally, the rootstock directly influences productivity, measured in grape volume per plant, and also the timing of ripening, slightly advancing or delaying the cycle of the scion variety. And perhaps the most important effect of all is the least visible in the short term: the vineyard's longevity. A rootstock poorly matched to the soil or local climate does not show up as a problem in the first harvest, but manifests years later, in the form of premature decline of the plant, precisely when the investment in establishing the vineyard has already been made in full and there is no longer any way to correct it without replanting.

A note on clones

Alongside the rootstock, there is also the decision of the clone, which we introduced briefly in Chapter 2. Different clones of the same variety can vary in productivity, cluster size, disease resistance, and even aromatic profile, and this choice is normally made together with the rootstock decision, since the two, together, form the plant's complete propagation material. There is no universally correct combination: there is the combination that is right for the land and for the project's goal.

What this means in practice

Consider two neighboring projects, on the same land already assessed in Chapter 1 and with the same variety chosen in Chapter 2. The first project chooses the rootstock by crossing the four criteria above: resistance to local pests, vigor compatible with soil fertility, adaptation to the land's physical and chemical characteristics, and expected productivity and longevity. The second chooses the rootstock most readily available at the nursery, without crossing these criteria.

Years later, the first vineyard maintains stable productivity and a slow decline curve, typical of a well-matched rootstock. The second may even produce normally in the first few years, but starts showing signs of stress, chlorosis, or premature decline, precisely when the investment in establishing the vineyard has already been made in full and there is no longer any way to correct it without replanting.

The central message of this chapter is direct: the rootstock is the invisible decision that sustains all the others.

Why COA treats the rootstock as a strategic decision

A poorly chosen rootstock is not a mistake that can be fixed later with more investment in the winery, the brand, or sales channels. It is a structural limitation: just like the land and the variety, the rootstock stays with the vineyard for decades, and correcting it means replanting.

That's why, at COA, the choice of rootstock is never treated in isolation. It is always cross-checked with the terroir already assessed (Chapter 1) and the variety already chosen (Chapter 2), to ensure the three decisions move forward together from the start.

This is the third chapter of the COA Insights series, on the decisions that turn a vineyard into a sustainable business. In the next chapter, we cover the fourth decision of the journey: vineyard establishment, the moment when row orientation, spacing, and mechanization come into play even before the first post is driven into the ground.

If you are evaluating which rootstock to use, or already have an established vineyard and want to review this alignment between rootstock, soil, and variety, now is the right time to talk: COA's Strategic Assessment Session. The amount invested is fully deducted if you go on to hire any of our other services afterward.

Subscribe to our newsletter and book your Strategic Assessment Session on the COA website: here. And follow COA Wine Business here on Instagram and LinkedIn to keep up with the next chapters of this series.

COA Wine Business Team

COA Wine Business. From soil to label.