BY Fred Peterson,
Peterson Winery, Healdsburg, CA

When I began working in California vineyards over 30 years ago, the choice of what type of nursery stock to plant was pretty simple. If you were in the Central Valley and root knot nematodes were not already a problem, you most likely planted own-rooted cuttings. If you were planting a vineyard in the North Coast, you either planted a rootstock rooting (either AXR-1 or St. George), or if you had planned a year in advance and had the money, you planted field-grown, dormant bench-grafts.

Regardless of the type of nursery stock used in a planting, it was very important that planting occur in the early spring. This would allow the plants to establish sufficient roots to supply the vine with water and nutrients after they had leafed out. Keep in mind that this was before the widespread use of drip irrigation.

Vine irrigation was done by furrow/flood or sprinklers in the Central Valley, and by sprinklers in the North Coast — either solid-set or movable pipe on the valley floor. In the hills or where water was scarce, hand irrigation from a tractor-pulled water tank was the only way to deliver water to a new planting.

Introduction of drip irrigation in the mid-1970s revolutionized many vineyard practices, especially the development of new vineyards. The ability to water on demand with very little labor or effects on cultural or disease control practices meant vines could be planted later in the year with much less risk of plant stress. Drip irrigation created a brave new world for vineyard owners/ managers and grapevine nurseries.

Below are various types of grapevine nursery stock produced and some pros and cons of their use.

Rootstock rootings
Rootstock rootings are almost always field-grown and sold as dormant plants, either directly from the nursery in late winter or early spring, or out of cold storage in late spring or early summer. As with dormant benchgrafts, rootstock rootings should be planted as early in the spring as soil conditions allow.

Planting dormant rootstock rootings after the beginning of June greatly increases vine mortality and generally decreases vigor and growth. Traditionally in the Central Valley and North Coast, these would be planted late March/early April, with the hope of enough spring rains to carry the plants through May before they would require irrigation.

“Fall budding” would be done as soon as mature budwood canes from the desired mother vines could be obtained, typically mid-August to mid-September. Besides the obvious skill required of the budders, having actively-growing plants, fresh/mature budsticks, and at least two weeks of warm, dry weather after the budding was done were all essential to a high percentage “take.”

In addition to the obvious caveat that the budwood be taken from virus-free mother vines of the proper variety/ clone, it is important the budwood be kept cool and moist and be used within a couple of days of being cut. If the plants stopped growing or had not achieved sufficient size, the budding would be postponed until the following spring, using dormant budwood which had been placed in cold storage.

The crucial management decision for spring budding (chip-budding) was budding as early as possible, in the spring, but after the weather had turned warm and without much likelihood of rain. These requirements could be problematic on the North Coast.

Though rootstock rootings are less than half the cost of any grafted plants, the additional costs of field budding and associated hand labor, when combined with the greater management requirements and risk, make this approach less desirable today, especially given the availability of excellent quality, reasonably-priced bench-grafted vines.

For a grower willing to take on the additional risk and management, planting rootstock rootings does spread out a portion of the establishment costs and it gives the grower additional time (as much as one year) to decide what variety/clone to graft. This can be very important if you’re planting a vineyard without a pre-plant contract.

Field-grown, dormant bench-grafts
These vines were grafted in the winter (usually at a bench in a nursery), callused (the union of scion/rootstock) in the spring, and planted out in a field in rows. After one growing season in the nursery, the plants would be dug that winter, sorted, graded, and bundled. The vines would then be either heeled in sand or put in cold storage until planted.

Field-grown bench-grafts have the obvious advantage of having established a solid graft union and a well-developed framework of roots prior to being planted in a vineyard. Because of the significant additional labor and expense to grow these grafts in the field for one year, nurseries typically produce very few of these vines without a written contract from a prospective grower, usually with a deposit required. This requires that the grower select the scion/rootstock combination and the number of vines to order at least 15 months prior to actually planting of a vineyard.

In planting field-grown, dormant bench-grafts, one important consideration should be how quickly the vines can be planted in the spring. Though two to three months of proper cold storage won’t harm the plants, for every week in cold storage past April the viability decreases and the potential for transplant shock increases.

If a vineyard owner wants to achieve the maximum benefits from planting dormant bench-grafts, all soil preparation and any installation of underground drainage and irrigation mainlines must be completed by early fall, depending on growing area. This allows planting to occur before summer, even in years with late spring rains.

Bench-grafts, green-growing/dormant
The first green-growing bench-grafts were spindly, delicate-looking little vines growing in wax paper tubes. When planting these vines, we were concerned about tearing enough of the wax paper tube so the roots could grow laterally without breaking too many roots.

Today, green-growing vines are allowed sufficient time at the nursery to obtain adequate root and shoot growth prior to being shipped as ready-to-plant. The larger the sleeve or tube that the vines are grown in, the greater the root mass that can be obtained prior to planting in a vineyard, and the more quickly the vines will begin shoot growth and achieve considerably more growth than a vine with a less-developed root system.

Bench-grafts grown in containers have many advantages over their field-grown cousins. First, they have not been grown in a field in soil that might have become infected with soil-borne pests and/or pathogens. Ideally, they are grown in a sterilized, specially formulated planting mix to maximize root development for the young grafts.

The second major advantage is that green-growing bench-grafts are not subjected to being placed in cold storage and to the artificial dormancy that it imposes on plants. Planting green-growing bench-grafts allows the vineyardist to plant his vineyard anytime from late spring when that year’s green grafts are ready for planting, through the summer.

Fall planting, though traditionally not done much in California grape growing, is one use of green-growing vines that has good possibilities in areas where early fall frosts are not a factor. Once a green-growing bench-graft has gone completely dormant in the winter, it is basically the same as a field-grown bench-graft in terms of root development and potential growth when planted in the spring. Again, these plants don’t have the potential downside of cold storage.

Even after leafing out in the spring, one-year-old green-growing vines will take root and begin growing immediately, provided that a drip system is operating and proper soil preparation was done.

With green-growing vines, proper hardening of the plants in the open air is very important. Taking green-growing plants directly from a temperature- and humidity-controlled greenhouse and planting immediately in a field is a recipe for disaster.

Preparing to plant
Whether planting or replanting, a vineyard is both figuratively and literally developed from the ground up. Having a thorough understanding of your soil and site is crucial to developing the best vineyard possible for that location. This includes soil depth, structure, chemistry, drainage, and erosion potential.

It also includes a previous crop history for the site and a thorough nematode screening. Talk to the viticulture farm advisor and nearby grape growers to learn what has worked in the area. Even more important, what has not worked well and what they would do differently in future plantings.

In 15 years of replanting vineyards on AXR-1 rootstock to phylloxera-resistant rootstocks in Sonoma County, I have become aware of many good phylloxera-tolerant choices, but very few nematode-tolerant choices.

As vineyards in the North Coast are replanted, soil/site preparation is very important. With the phase-out of methyl bromide as a pre-plant fumigant and the desire to use softer chemicals in vineyards, it is increasing difficult to avoid the “replant syndrome” by going immediately back into ground with grapevines where the previous crop was grapes.

The most important operation in replanting is to do a thorough job of removing old grapevine roots. After removing the vines themselves (preferably using a method that removes the root crown and larger roots with the trunks), the best way to remove most root-pieces is to deep-plow the field with a large enough crew to keep up with the plow, and a tractor with trailer to haul roots to a burn pile.

Fallowing a field for a couple of years with appropriate cover crops is the best method for reducing pest/pathogen populations. However, most growers can not afford to leave the ground out of production that long. Amending the soil with whatever nutrients are marginal, and either lime or gypsum if necessary, is best done during soil preparation.
Once you decide what type of planting material and what scion/ rootstock combination(s) you will use, you will need to choose a nursery from which to order the vines. There are many factors that should affect this decision. First and most important is to only work with nurseries that are well established and that have a reputation for producing high-quality, disease- and pest-free vines.

It is a good investment to take time to tour prospective nurseries. Ask questions about procedures and practices in the grafting and care of newly-grafted plants. Pay particular attention to sanitation practices used and the general cleanliness of the facility, especially the grafting room.

Some nursery practices that will lead to better quality vines include the proper matching of the scion diameter to the rootstock diameter. A good match will allow complete callus development and subsequently a strong graft-union.

Does the nursery use a hot-water dip and a preventive insecticidal treatment to prevent introduction of pests, especially the vine mealybug, into your vineyard? What are the protocols for testing plant materials to ensure they are free from known pathogens and pests? Does the operation appear organized and managed well?

Is the nursery capable of working with you in being able to hold vines until the vineyard is ready for planting and the vines are fully developed? This flexibility of the nursery can be crucial in maximizing future vine growth and health. Does the nursery’s field representative bring sufficient expertise to help you achieve your goal?

Unlike almost all other costs associated with vineyard development, the cost of vines has increased very little in the last 25 years. However, greater plant densities are much more common in the North Coast, and the number of vines per acre has, at a minimum, doubled from early 8 x 12 (454 vines per acre) trellised plantings.

In many vineyards, planting densities have tripled or even quadrupled. This not only makes the cost of the vines a larger expense, but the labor of planting and hand-vine care needed to ensure desired growth from the vines becomes a larger portion of the total development cost. Therefore, the choices of what and when to plant are even more crucial.

Summary
Viticultural technologies and techniques have evolved a great deal in the last 20 years, allowing much more choice in how and when a vineyard is planted. However, along with the increased flexibility have come much greater costs to develop an acre of winegrape vines and a much smaller margin for those who don’t do it well.

Using the best available plants and plant materials is certainly among the most important decisions a grower/ vineyard manager makes in developing a new planting. However, these vines must be integrated with the proper site evaluation and soil preparation in order to maximize the vineyard’s potential. Though much has changed in vinegrowing in the last couple of decades, the basic horticultural realities of plants, climate, and soil is pretty much the same as its been for millennia.

After receiving a Viticulture/Enology degree from U.C. Davis in 1978, Fred Peterson has held a number of winegrowing positions including winemaker/general manager at Mount Eden Vineyards (Saratoga, CA), and vineyard manager for Ridge/Montebello Vineyard (Cupertino, CA). In addition to managing Peterson Winery estate vineyards in Dry Creek Valley (Healdsburg, CA), and various vineyard consulting on 650 acres over 16 years, he is the Duarte Nursery field representative for Sonoma County and Anderson Valley.