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An Illustrated Guide to Field Grafting Grapevines

Notes: The grafting techniques described and illustrated in this guide were developed and refined by José Olguin, of Napa, California. Special thanks to Dai Crisp of Temperance Hill Vineyards for his photographs of José Olguin’s grafting team working in the Willamette Valley. All photos are © 1999 Dai Crisp, and are not intended for reproduction. Photos may be used with prior written permission for educational purposes only. Please Contact Webmaster for permissions.

Introduction

Field grafting, also known as top-working, is an old technique for changing the fruiting variety in a vineyard without the expense of replanting, and a loss of only one year of cropping. The field grafting technique involves cutting off the top of an established grapevine and inserting into the trunk two (usually) 2-bud canes of the variety selected for fruit production. The end result of a successful graft is a two-variety grapevine; the original vine continues as the root system and lower trunk, while the new variety becomes the upper trunk and the fruiting portion of the vine.

Conversion of a vineyard to a different variety usually can be accomplished in one season. The quick resumption of fruit production is a major advantage of the technique, enabling the vineyard manager to respond to shifting market demands or correct a mistake in the initial selection of the fruiting variety. Field grafting, however, is only appropriate for very specific circumstances.

Vineyards that are candidates for field grafting should have all of the following characteristics:

  • Fruiting variety is uneconomical to grow or is inappropriate for the site.
  • Vines have healthy growth and are relatively vigorous.
  • Vines are not infected with crown gall or serious viruses (i.e., leafroll, fanleaf).
  • Vines are growing on phylloxera resistant rootstock.
  • Rootstock variety is appropriate for the site and the new fruiting variety.
  • Vines are relatively young with many productive years remaining.
  • Row and vine spacing is desirable and appropriate.
  • Trellis system is in good condition.

In some circumstances, self-rooted Vitis vinifera vines, which are susceptible to phylloxera, are field grafted to a new fruiting variety. The strategy is to get enough years of profitable crops with the new variety to more than pay for the grafting costs before phylloxera infests and destroys the vineyard. Such a strategy is a gamble in regions growing Vitis vinifera with phylloxera present, but could prove economically beneficial in the short term.

Hiring an experienced grafting crew, which is the assumption of this guide, is estimated to cost approximately $1.50 per vine. Additional costs are incurred for collecting or purchasing the scion wood, and performing pre-grafting preparations and post-grafting care procedures.

Carefully evaluate your vineyard to determine if it is a suitable candidate for field grafting. If you conclude that it is suitable, plan ahead to give yourself plenty of time for all of the necessary preparations. The grafting process itself is not as simple as it appears, and requires considerable practice to develop the skills. You may want to consider hiring an experienced grafting crew. This guide presents the field grafting technique from the perspective of using a professional crew to make the grafts. The techniques described in this guide were developed and refined by José Olguin of Napa, California. The first (Pre-Grafting Preparation) and third (Post-Grafting Care) stages of the grafting process are conducted by the vineyard manager and resident crew.

The grafting procedure is described in three stages. Stage 1, Pre-Grafting Preparation, focuses on collection and storage of scion (fruiting variety) wood. The Grafting Process (Stage 2) contains step-by-step descriptions and photo illustrations of a professional grafting crew performing the cuts, inserting the scion, and taping and waxing the grafts. Stage 3, Post-Grafting Care, emphasizes the critical practices necessary for successful graft healing and subsequent healthy growth of the scion.

Pre-Grafting Preparation (Stage 1)

Scion Wood Collection

Grafting success is highly dependant upon the quality and size of the scion wood. Scion should be collected only from healthy plants in a strong section of the vineyard, exhibiting no stress or disease problems. Canes that have been well-exposed to sun are preferred, as opposed to shade canes. If you are purchasing or taking scion from another vineyard, make sure you verify with your provider the quality, cleanliness, and health status of the mother plants.

Scion should be collected during the winter months, preferably in January or February. Avoid taking wood after a “freeze event” to lessen the likelihood of collecting damaged buds or canes. The buds should be dormant and well hardened off.

Larger caliper scion is necessary for field grafting than that typically used for bench grafting. Look for canes that are 5/16″ to 9/16″ in diameter and round, not flattened on one side. Cane length can be up to approximately 2 ft. long. Make a flat cut on the bottom end and an angled cut on the top of the cane to help maintain the canes in proper orientation. Cut canes so that there is plenty of stem extending on either end so that fresh cuts can be made on grafting day during scion preparation. For the most efficient use of scion wood, canes should be cut so that the bud count is in multiples of 2, since each scion piece grafted will have 2 buds. Collect enough scion wood to supply two scion pieces per grafted vine, plus an additional 10% to ensure a good selection of suitable wood for grafting. Be sure to keep canes moist during collection.

Storage

Keep canes moist and cool during storage. Bundle canes in groups of 100, oriented with the tops (angled cuts) together, and wrap in pre-moistened newspaper. Label each bundle with the variety name using a permanent label, and place in a plastic trash bag or other “air-proof” poly bag to prevent moisture loss during storage. Seal the bags and put in cold storage just above freezing (34-36oF). Canes should only be removed from storage on the day before grafting. Place bundles (still in their bags) in a shady, cool location to enable a gradual rise to ambient air temperature. Take out only enough for one day’s worth of grafting, and leave the remainder in storage.

Optimal Time for Grafting

The best time for field grafting is late spring when the vines are starting to push new growth. Try to graft when the vines are dry to reduce the risk of diseases.

The Grafting Process (Stage 2)

Field Preparation

Vineyard staff, and not the grafting crew, are responsible for much of the pre-grafting vine and field preparations. Make sure you have adequate staff on hand to stay well ahead of the grafter’s pace, as these professionals are normally paid by the graft. There is typically one grafter per row, working one row at a time until the row is completed.

Trunk Cutting

On grafting day, the vineyard staff is responsible for cutting off vine trunks ahead of the grafting crew. Determine the desired height of the head on the new vine before cutting. Since field grafting provides an opportunity to change training systems, such decisions may affect where the trunks are cut. If a new head height of 28″ is desired, then cut the trunk just below that height (approximately 24″). This cut should be made at a clean, unblemished surface area of the trunk. Try to be as accurate in cutting height as possible, yet efficient. If vine trunks are approx. 1½” to 2″ in caliper, it is possible to use large loppers for the cut. Any trunk larger than 2″ may require a chainsaw; handsaws are slow and inefficient. Make sure you have enough tools for the vineyard staff to stay ahead of the grafters. The vineyard crew should clear away and dispose of any brush that might hinder the grafters’ progress.

Basal Trunk Incisions

Make two small diagonal incisions about 1/4″ deep, just into the cambium, one each on either side of the trunk near the base, to allow the vine to “bleed”. This must be done before the graft is made, since there is a likelihood that the pressure from sap flow will push the graft out. A fine-toothed hand pruning saw is adequate for making these simple cuts.

Scion Preparation

Scion Preparation

Scion Preparation

The first task for the grafting crew is to prepare enough scion wood for the day. Consult with the grafting crew to determine the number of vines to be grafted each day. The canes from storage are cut into 2-bud lengths using hand shears, and must be kept moist.

Grafters Toolbox

The grafting crew often uses a modified wooden carpenters toolbox to carry their supplies. One side holds the prepared scion and the other holds two sharp, high quality grafting knives, grafting tape, and hand shears. The scion is pre-soaked in water and covered with a moist towel. (Note the large-sized caliper scion and wet towel on the box handle.)

The Grafting Cuts

Grafting Cuts: Face Cut

Face Cuts

A face cut is made at the top side of the trunk aligned along the grapevine row. This cut is repeated on the other side of the trunk. It is preferable to have the two face cuts parallel to the vine row so that the fragile new shoots growing from the graft are close to the supporting trellis wires. The face cuts may not always be made exactly parallel to the row, but could be somewhat offset, depending on the quality of the trunk surfaces available. The best surface area is always chosen for the cut.

Grafting Cuts: Diagonal Incision

Diagonal Incisions

For each face cut, two parallel incisions are made downward into the trunk at approximately a 30o angle. The first incision starts approximately 1/4″ from the bottom of the face cut, and the second is placed midway up the face cut.

Grafting Cuts: Diagonal Incision

Diagonal Incisions

The second diagonal incision is made midway up the first face cut.

Second Face Cut and Diagonal Incisions

Repeat the steps above, making a second series of face and diagonal incisions on the trunk opposite the first set.

Scion Preparation in the Field

Scion preparation employs three different cuts that are intended to match the face cut incisions made on the trunk:

  • Diagonal Face Cut
  • Tip End Cut
  • Mid-Face Incision

Scion Preparation in the Field: Preparation at Vine Site

Diagonal Face Cut

A very long diagonally slanted face cut is made on one side of the bottom end of the scion, approximately the same length as the face cut on the trunk. Make sure the scion is correctly oriented (top and bottom) before making these cuts.

Tip End Cut

The scion is turned over to the opposite side and the tip is cut back diagonally, creating a sharp edge at the tip.

Scion Preparation in the Field: Scion Face Cut Incision

Scion Face Cut Incision

A small incision is made near the middle of the face cut, parallel to the scion.

Scion Preparation in the Field: Illustration, Scion Preparation Cuts

Finished Scion Piece

The illustration shows the three types of cuts made to the scion.

Scion Placement on Trunk

Scion Placement on Trunk: Scion Tapped into Place”

Scion is tapped into place

Correct placement of the scion piece is critical for a successful graft. The cambium layers of the trunk and scion piece must be in contact with each other to enable the two tissues to grow together into a healthy graft union. The scion piece is placed at one end of the face cut, where the trunk’s cambium layer (just beneath the bark) is exposed. Matching cuts in the scion and the trunk enable a snug fit when the scion is gently tapped into place with the grafting knife.

Scion Placement on Trunk: Scion Placement

Scion Placement

The scion is placed into position. Note how the scion is offset to the edge of the face cut.

Scion Placement on Trunk: Scion Placement

Scion Placement

Note how the scion is lined up to one side of the face cut, not centered in the face cut. Proper alignment enables optimal cambium contact of the two faces, facilitating callous formation and healing of the graft. If the scion is positioned in the center of the face cut there is little, if any, cambium contact and the graft will likely be unsuccessful.

Taping the Graft

Taping the Graft: Scion being Taped

Scion being taped

Grafters use a special 1″ wide grafting tape to carefully, yet firmly, tape the graft into place. The tape can stay in place until it breaks down from weathering.

Taping the Graft: Graft Taping Completed

Graft Taping Completed

The grafting crew’s job is finished after the graft is taped. All remaining procedures are carried out by the vineyard crew.

Post-Grafting Care (Stage 3)

Sealing the Graft

Sealing the Graft: Graft Area being Sealed

Sealing the entire graft area.

Sealing the graft union helps keep it from drying out. Soon after the graft has been taped, the entire area is completely sealed; including all the tape, the exposed cut on top of the trunk, and the tips of each scion. The vineyard crew is responsible for applying the graft sealant, but consult with the grafting crew on which product is preferred and who will provide the product. Henry Tree Seal is one commonly used sealant for field grafting.

Use inexpensive disposable bristle brushes, 1½” wide, for applying the sealant. The brushes are not cleanable or reusable at the end of the day. A milk jug with the top cut off, leaving the handle portion intact, makes a good bucket for the sealant and brush. Have a good supply of inexpensive cotton gloves for your crew; new gloves will be needed daily.

Sealing the Graft: Sealing Scion Tip

Sealing the Scion tip

Sealant is daubed on the tip of each scion

Successful field grafting requires diligent care of the vines throughout the growing season. There are three areas of importance in post-grafting care:

  • Monitoring and relieving vine pressure
  • Managing Suckers
  • Supporting new growth

Monitoring and Relieving Vine Pressure

Soon after grafting, a monitoring schedule should be developed for the management of sap bleeding, especially at the graft site. The pressure of sap flow must be relieved to prevent the scion from being pushed out of contact with the trunk cambium. Make two small diagonal incisions about 1/4″ deep, just into the cambium, one each on either side of the trunk near the base. The trunk incisions enable most sap flow to escape before reaching the graft site. The first series of cuts are made by the vineyard staff during the trunk cutting stage. Subsequent cuts, just above the original cuts, should be made every 5 to 7 days. Additionally, all vines should be inspected every few days, beginning 3 days after grafting, for bleeding at the graft site. This is especially important during periods of warmer weather, when sap flow tends to increase. Any time that bleeding is seen at the graft, or previous trunk cuts have stopped bleeding, new trunk cuts should be made.

Managing Suckers

Although standard vineyard management practice prescribes their removal, trunk suckers can serve an important function for the field-grafted vine. Suckers divert sap pressure from the healing graft union and sustain the original vine if the grafts fail. Consider saving one strong dominant sucker, preferably on the upper trunk, to provide new wood upon which to graft, if necessary. Allow suckers to grow until the buds are showing strong growth, at least one foot long. The shoots may require 4-6 weeks to become well established, then suckers may be removed.

Supporting New Growth

The graft union remains in a fragile state while the new shoots are growing and is susceptible to damage from wind shaking the shoots. New shoots should be tied to the trellis wires for support as soon as they reach a length of 12-18″

Additional Considerations

Grafted vines have variable growth rates. Buds may start to grow in just 3-4 weeks, or some may take up to 4 months or more before they develop a strong shoot. Be patient and continue to manage the suckers, make bleeding cuts as needed, and train the shoots throughout the season.

Treat the vines with the same care that you give to newly planted vines with the following exceptions. Irrigation is generally not recommended in the first year, unless the vineyard is located in a low-rainfall region like the Rogue district of southern Oregon. Similarly, nitrogen fertilization is generally not recommended during the grafting year unless the vineyard has a history of deficiency. Micronutrients, such as boron and zinc, should be applied if needed. Diseases, particularly powdery mildew, should be controlled to facilitate growth of strong vines. If fungicide sprays are made with an airblast sprayer, use the lowest fan speed possible to avoid blowing the shoots around and potentially weakening the graft union.

Successful field grafting can result in vigorous shoot growth that enables the vine to produce a crop the next year. Avoid overcropping grafted vines in their first year; balance the crop load with the size of the canopy. Vines with failed grafts can be grafted again in the following year if suckers have kept them alive and strong.

Michael J. Coe1, Dai Crisp2, and Edward Hellman1, Oregon State University, North Willamette Research & Extension Center, 2Temperance Hill Vineyards