Vineyard design is an exercise in fit: aligning the vineyard system, variety and clone, rootstock, trellis and row design, and irrigation capacity, with site conditions (soils, water, topography), regional climate and defined production and quality goals. Plant material that harmonizes with soil, water and weather will outperform the same variety planted out of place. Among the most powerful and longest-lived levers growers control is plant material selection: the choice of variety, the specific clone that represents that variety and the rootstock that interfaces with the soil.

The interaction of those choices, layered onto site, climate and seasonal management, shapes vine vigor, yield stability under increasingly variable seasons, water use, fruit composition and ultimately wine style. As temperatures trend upward, seasons swing wider and precipitation arrives in bigger pulses separated by longer dry spells, the case for deliberate plant selection has never been stronger. Getting plant material right at planting does more than set up the next crop year; it establishes a strategy for productivity and resilience over the life of the vineyard.

In practice, climate adaptation in vineyards operates on two levels. Long-term strategies are established at planting and redevelopment: varietal choice, clone (treated as a site-specific hypothesis), rootstock, row spacing and orientation, and trellis architecture. These decisions align vine physiology with site constraints and provide benefits over the life of the vineyard.

Short-term strategies are seasonal and event-based (think heat and sunburn mitigation through the use of shade cloth or particle films, canopy and crop load adjustments, irrigation scheduling and deficit tactics, cover crop and soil moisture management as well as frost and smoke readiness.) They must be adjusted each year to observed weather conditions.

Both levels of adaptation are important as they can provide increased benefits, especially when stacking practices. This article focuses on the long-term lever of plant material selection while noting how they interact with short-term practices. If you get plant material right, every other management decision gets easier.

Rootstock-Driven Adaptation
The modern role of rootstocks extends well beyond phylloxera control. Root systems influence rooting depth and distribution, the efficiency of water and nutrient acquisition, and tolerance to water deficit or excess and soil pH and salinity. Differences in rooting depth and density, hydraulic conductance and nutrient uptake capacity are traits inherited from rootstock parentage.

These physiological traits influence canopy size and shoot growth rate and affect the vine’s ability to maintain turgor and photosynthesis during heat or water deficit, ultimately determining productivity under environmental constraints.

In practical terms, rootstocks help growers tune the relationship between available water, canopy demand, site and climate. A stock that tends toward deeper rooting can mine water from deeper in the soil profile, while a rootstock that produces shallow roots will not have the same access to water deeper down. High-vigor rootstocks with larger canopies might use more water than the same variety on a lower-vigor rootstock.

The aim of rootstock selection is balance. On inherently low-vigor sites, a higher-vigor stock can build a functional canopy and yield, while on sites with deep, fertile soil and plenty of access to water, a moderate- to lower-vigor stock keeps canopies proportionate, improving fruit exposure and stabilizing ripening while reducing the risk for powdery mildew by increasing canopy porosity and spray penetration.

Because these effects play out every year, rootstock selection is one of the most reliable paths to steady yield and fruit composition under different weather conditions from year to year. Compared with clones, the research base for rootstocks across sites and water regimes is relatively mature, giving growers a clearer starting point for matching stocks to their site constraints.

Varieties and Clones: Opportunity, Limits and Ongoing Work
Variety choice sets the broadest frame for wine style and agronomics. Cabernet Sauvignon does not behave like Pinot Noir, nor should anyone expect it to. Within each cultivar, clones offer an additional level of control. They can differ in cluster architecture, berry size, ripening tempo and the potential balance of sugar, acid and phenolics. They can also modulate canopy architecture and stress responses in ways that matter for climate resilience.

At the same time, it is essential to be clear about what we do not yet know. For major cultivars, there are dozens, sometimes hundreds, of recognized clones. Only a small fraction have been rigorously compared across diverse soils and climates. The result is a patchwork of information: promising observations at particular sites and in individual seasons, but far from a universal playbook.

Regional market incentives add pressure to favor specific varieties, so clone selection provides an important source for climate resilience. However, those differences are still being charted. At this point, the responsible approach is to treat clone choice as a hypothesis to be tested locally.

On-farm trials that compare a few candidate clones, managed identically and observed over several seasons, may yield more insight than borrowing a conclusion from an unrelated site.

Site First: Limitations Drive the Right Choices
Sound plant selection begins with an honest accounting of site limitations. Soil depth, texture, pH, salinity and compaction define rooting opportunity. Historical and current nematode pressure can determine whether a replanting will thrive or stall. Access to water, both stored in the soil profile and delivered through irrigation, sets the ceiling for sustainable canopy size and crop load. These constraints are not inconveniences to be managed around after planting; they are design parameters for the planting itself.

Matching root system behavior to these parameters reduces the need for midseason interventions. In deeper, well-drained soils with limited water allocations, a stock with deeper rooting and moderate vigor may help vines maintain function into late summer without excessive canopy growth. In cooler, heavier soils with ample water, a more riparia-influenced stock might efficiently use available moisture without pushing excessive vigor.

Rotating genetic lineage groups between replants may also disrupt the development and buildup of site-adapted soil pests, similarly to crop rotation in annual systems. The goal is not to find a perfect vine, but to assemble a combination that minimizes the site’s liabilities while amplifying its strengths.

Oakville Rootstock × Cabernet Sauvignon Clone Trial: Findings from One Site
The UC Davis Department of Viticulture and Enology’s Oakville Station is a 40-acre research vineyard in the heart of Napa Valley, with two research blocks, South Station and the Old Federal Vineyard, and an on-site laboratory complex. For more than five decades, it has hosted applied trials on clones, rootstocks, vine spacing, pruning and irrigation that directly inform California winegrowing.

One current study, the Oakville rootstock × Cabernet Sauvignon clone trial, offers a timely example of how rootstock and clone interactions with site and season converge. The trial is composed of four rootstocks, 5BB (berlandieri × riparia), 110R (berlandieri × rupestris), 420A (berlandieri × riparia) and 3309C (riparia × rupestris), planted in 2016.

The vines were field-grafted in 2019 with four Cabernet Sauvignon clones: Foundation Plant Service (FPS) Clone 8 (CS8, originally sourced from the Concannon Vineyard in Livermore in 1965), FPS Clone 54 (CS54, a Concha y Toro selection introduced under USDA ARS PI #364302), FPS Clone 65 (CS65, Fountaingrove selection A, sourced from Ridge Vineyards in the Santa Cruz Mountains) and FPS Clone 30 (CS30, the Disney Silverado heritage selection collected in 1989). The block is farmed under moderate deficit irrigation (60% ETc).

Starting in 2022, the first full production year of this block, yield and fruit quality data have been collected and performance evaluated (2022, 2023 and 2024 seasons reported here). These results provide an early look at a very promising trial that will provide insight into climate-resilient Cabernet Sauvignon clones and rootstock combinations.

To complement yield components and fruit composition data, our team used drone imagery collected over the 2023 and 2024 seasons to quantify some aspects of vine physiological performance (Fig. 1).

Vine Performance
To date, 5BB has supported the largest measured canopy surface area and among the highest NDVI values of any of the rootstocks in the trial (Table 1). CS8 consistently maintained lower canopy temperatures relative to CS54 and CS65, suggesting better plant water status, allowing for greater transpiration cooling of the canopy and exhibiting greater stability in yield and fruit metrics (Table 2) under variable conditions over the three years of study.

CS54 often showed higher canopy stress, expressed as lower NDVI and warmer canopies, while CS65 tended to produce a smaller canopy than CS8 or CS54 yet maintained an average NDVI.

These are useful findings, not prescriptive recommendations. They tell us that, in the early years of the Oakville rootstock clone interactions trial, under growing conditions and management practices of Napa within the seasons studied, certain rootstock clone pairings exhibited favorable balances of canopy size and stress indicators, with higher productivity and improved fruit outcomes. Other combinations showed greater stress and lower productivity under the same conditions.

They do not guarantee similar behavior on calcareous benches in Paso Robles, on sandy loams in Lodi, or in mountain sites with shorter growing seasons. This trial aims to advance understanding of the complex nature of genotype by environment interactions but is far from comprehensive, and more work is needed to provide site-specific recommendations outside of the parameters of this study.

Efforts to expand coordinated rootstock × clone trials across diverse sites to identify the site-specific drivers of productivity and resilience, while also broadening the matrix of rootstock clone combinations, are needed.

The Oakville results represent the early productive years of this vineyard. As the trial progresses through dry and wet, hot and cool seasons, it will continue to yield longitudinal data on plant material performance over the typical life of a block. Farm-scale validations remain essential, but multi-site experiments will accelerate understanding of the complex interactions between planting material and environmental drivers of productivity.

Mechanized pruning in grape production aims to improve productivity by means of uniformity, timeliness and cost effectiveness. It also helps to address the farm labor shortage situation facing the grape industry. The difference in the outcomes of manual and mechanized pruning from the viewpoint of pesticide spray application to grapevines is minimal to nonexistent. Figure 1 shows examples of manually pruned versus mechanically pruned grapevines, indicating similarity in appearance. In both cases, the vine canopies undergo the same temporal changes, from non-foliated canopies at the beginning of the production season to fully foliated canopies later in the season.

As the number of leaves increase inside the canopy, the leaf area density (LAD) also increases. LAD, with units of square meters per cubic meter, is defined as the total leaf area (m²) per unit volume of canopy (m³). LAD represents the available leaf area in the target canopy that applied spray should deposit on. Figure 2 shows an example of the temporal variation of LAD in canopies of a of manually pruned grape over part of the season. Increasing LAD trends figure are attributed to rapid increase in canopy foliage as leaves form while decreasing LAD trends can be attributed to spreading out of the canopy due to limb elongation during the vegetative stage or gravitational effect as leaves and fruits weigh down on branches.

Hence, when considering spray technology needs or practice beyond pruning, there is virtually no difference between a manually pruned and a mechanically pruned vineyard. The same principles and best practices apply. In the San Joaquin Valley, about 76% of vineyard pesticide applications are done using conventional airblast sprayers, based on 2023 data. The remainder is done using tower sprayers (10%), electrostatics mist blowers (7%) and other sprayers (7%).

Basics of Spray Application
During spray application using any of the aforementioned sprayers, the sprayer travels between vine rows applying spray on both sides. Basically, the immediate vine canopies adjacent to the sprayer are considered the target canopies, and both sides of the canopy need to be sprayed to achieve full coverage. Standard sprayer calibration calculations view only half of the vine row per side as being sprayed at any given time. Therefore, it is sufficient and most efficient for the sprayer air to carry the spray to the target canopy with only enough penetration, as excessive penetration could reduce the level of spray deposition and increase drift potential. The volume of spray applied is calibrated as follows:

where GPA is gallons applied per acre, GPM_{2 sides} and GPM_{1 side} are the total flowrates (in gallons per minute) from all open nozzles, MPH is the calibrated forward speed (miles per hour) of the sprayer, and RS is the vine row spacing (feet).

Some other commercial sprayers are designed to treat multiple vine rows in a single pass. In such cases, the calibration formulas provided above should be revised accordingly to accurately calculate GPA. To do this, RS would need to be multiplied by the applicable values of 2, 4 or 6.

Considerations for Efficient and Effective Spray Application
Three components are important for achieving an efficient and effective application: the sprayer (equipment), the spray (material) and the operator or spray crew. The sprayer must be well-maintained to provide the intended functionality, well-calibrated to achieve accurate GPA in accordance with the pesticide label and well-adjusted to target canopy characteristics. This means the number of open nozzles should not result in too much spray applied over and/or under the canopy. In the actual application, the sprayer needs to be well-operated, maintaining the calibrated settings.

For effective pest control, the spray application must be properly timed both in terms of the target pest and the weather conditions at the selected time of application. The spray must also be accurately applied to achieve the intended dosage to control the target pest. To maximize this dosage, the spray should be well-directed to the target canopy. The pesticide mix should be optimized for both coverage and on-target deposition to prevent excessive runoff of spray liquid from leaves. The level of air assistance from the sprayer should be appropriate for adequate penetration. The need for air assistance in vine and tree spray applications is well established and cannot be overstated. However, research studies demonstrate using too much air assistance can result in reduced on-target deposition and increased drift potential due to overpenetration.

Furthermore, the success of an application depends on the skill and knowledge of the operator or spray crew. They should be familiar with spray application best practices and be willing to adhere to them. They should be attentive to sudden changes in the field (e.g., an abrupt change in wind speed and/or direction toward a sensitive site) and be able to delay or postpone applications until a more suitable time.

Whether applying spray to a manual or mechanized pruning vineyard system, effectiveness is not just about achieving the desired GPA. More than that, it is about getting adequate spray material to the target so the desired levels of spray coverage, on-target deposition and pest control can be achieved. Afterall, spray that deposits on the target is the spray at work.