Basic Principles of Pruning Backyard Grapevines

Growing grapes has been a long tradition in many home gardens. Gardeners truly enjoy the fresh taste of homegrown grapes; however, the work to maintain grapevines can be a challenge. As with other fruit crops, grapevines need weeding, fertilizing, insect and disease control, and proper pruning to assure a bountiful harvest. For more information about homegrown grapes, refer to the OSU Extension fact sheet, Growing Grapes in the Home Fruit Planting at ohioline.osu.edu/factsheet/hyg-1423.

Proper training of grapevines is essential to maintain plant size, shape and productivity. If left unattended, grapevines can become unruly, and fruiting will be poor due to overproduction of vegetation. This fact sheet is intended to help home gardeners gain a better understanding of the principles of grapevine pruning and the selection of training systems. Refer to the glossary of terms (on the last page) if you are not familiar with some of the terms used in this fact sheet.

In the first two years, it is important to determine what training system to use and prune grapevines accordingly. When the vines are mature, pruning can involve dealing with a considerable amount of vegetation. This will require some skill to properly prune, effectively manage the foliage and maintain adequate fruit production year after year. Additionally, the variety of grapes and the trellis or arbor system used will determine the extent of pruning that is required.

What kind of training system should I choose?

Selection of a training system definitely determines how you would prune your grapevines. Many gardeners prefer the high cordon system (Figure 1a) since it is relatively simple to establish and maintain where others like to incorporate a grape arbor into their landscape. Young vines are carefully trained to either one or two trunks. The fruiting area is established as either head-trained (Figure 1b) with canes (hardened-off shoots), permanent cordons (horizontal arms) with dormant canes pruned back as spurs, or a fan-shaped arrangement on top of a four-post arbor structure.

In a cane-trained system, new canes are laid down each season. Grapevines under this system are generally head-trained at the top wire. New shoots that are produced during the growing season harden-off as canes with a reddish-brown color and will be approximately pencil size in diameter. Two of these canes are selected and tied down to the top wire; one cane is laid down in each direction. Canes can be tied using pieces of cloth, twist ties or plastic stretch tape. Buds are counted and the number is adjusted according to the desired fruit load.

Cordon-trained systems are different in that new spurs are established each growing season as one-year-old canes and are pruned back to three to four buds per spur. When growing grapevines on an arbor, the fruiting wood may be either one-year-old canes or spurs that are attached to cordons positioned on top of the arbor.

Figure 1a. Bilateral high cordon system. Figure 1b. Head-trained system.

Do I prune American, French-American Hybrid and Vinifera varieties differently?

Pruning practices vary a great deal based on the type of grapes grown. American and French-American hybrid varieties are more commonly grown in home gardens than Vinifera varieties since they are more winter hardy and disease resistant. Vinifera varieties tend to be grown by more advanced grape gardeners.

American, French-American hybrid, and Vinifera varieties differ in the amount of fruiting wood that is produced annually. American cultivars tend to have the greatest amount of vegetative growth followed by French-American hybrid varieties. Vinifera varieties have the least amount of foliage.

The amount of one-year-old wood to be left after pruning is dependent on the amount of vegetation produced during the previous growing season. The 30+10+10 balanced pruning system can be used to determine the number of buds to retain on the vine based on the weight of one-year-old wood pruned off.

For example, a vine that has three pounds of wood pruned off will have 30 buds left for the first pound and 10 buds left for each of the second and third pounds of wood. A total of 50 buds will be retained. If more than 3 pounds of wood were produced in the previous growing season, additional buds would need to be retained to help balance the crop load.

A grapevine will over-compensate with increased foliage if there is not a proper amount of fruit load to store carbohydrates produced in the leaves. If the appropriate number of clusters is left on a grapevine, there should not be a lot of excess foliage produced.

What is shoot positioning?

Grapevines that have not been pruned can appear to be quite tangled unless the gardener has carefully “combed” (shoot positioned) the vegetation during the growing season. Shoot positioning results in high-quality fruit, better buds for next year’s crop, reduced number of shoots that are tangled, improved sunlight exposure, and more air circulation.

As Figure 2 shows, a non-combed vine will have several one-year-old canes trailing in different directions. In Figure 3, the combed vine is much neater, easier to prune, and will produce better fruit and canes.

Figure 2. Non-shoot-positioned grapevines. Figure 3. Shoot-positioned grapevines.

How do I properly prune grapevines?

All one-year-old canes that grew along the cordon will be pruned back to either three- to five-node spurs as fruiting wood or one-node renewal spurs as vegetative wood. The cut end of the spur should measure at least pencil size in diameter. Renewal spurs produce vegetative shoots that are used for the following year’s fruiting wood. Grapevines are normally considered to be mature and fully productive in year three. Dormant pruning should be completed starting in late February through March. One-year-old wood (the previous summer’s growth) should be pruned back to three to five nodes per spur. The spurs should be evenly spaced along the cordon.

To determine how many buds to retain for fruiting will depend on how much vegetative growth occurred the previous year. You may use different approaches for determining the number of fruiting buds. With any pruning system, at least 85 to 90 percent of the one-year-old wood will be removed during dormant pruning. This will allow the grapevines to maintain their structure (shape), distribute fruit load along the cordons, and enhance fruit quality. On three-year-old (or older) vines, approximately 40 to 50 buds will be kept.

What are the tools used for pruning?

Hand tools such as loppers, hand pruners and handsaws can be used to effectively remove all undesired wood from grapevines. Select the appropriate tool to remove wood as cleanly as possible to avoid unnecessary injury to the plant. Hand pruners can be used to effectively remove one-year-old wood. If the wood is two- or three-years-old, it is suggested that a lopper or saw be used to cut through the heavier wood.

Summary

Learning to master the art and science of grapevine pruning takes time and practice. Contact your county Extension educator for updated information on pruning. Make sure your grapevines are pruned each year to maintain the size and shape of the grapevines, maximize fruit production, and increase the overall fruit quality.

Glossary of Pruning Terms

Cane: A green summer shoot matures (hardens off) into a woody, brown one-year-old cane after leaf fall. Cordon: A permanent extension of the grapevine’s trunk that is horizontally positioned along the trellis (arbor) wire. Fruiting Wood: One-year-old wood that produces the current season’s shoots and fruit. Pruning: Removal of portions of a grapevine for the purpose of maintaining size, shape and productivity. Renewal Spur: A cane pruned to one node with the primary purpose of producing a vegetative shoot (cane) for next year’s fruiting wood. Shoot: The green, leafy growth that develops from the compound bud that normally produces fruit clusters. Spur: A cane pruned to three to five fruiting nodes to produce shoots bearing fruit clusters. Trunk: The main, upright structure(s) of the grapevine from which cordons, shoots and canes arise.

Useful References

  • Ohio State University Extension Bulletin 919: Midwest Grape Production Guide.
  • Ohio State University Extension Bulletin 940: Midwest Home Fruit Production Guide.

Don’t be timid when pruning grapes

“Home grape growers don’t prune their vines enough,” said Strik, who is the author of Extension’s Growing Table Grapes publication. “When gardeners prune, they should remove the majority of wood produced the previous season – until about 90 percent is pruned off.”

That’s a lot. But look at it this way: There’s no need to evaluate shape and size like when you cut back shrubs and trees. The instructions are straight-forward and illustrations and photos in Strik’s guide, which includes information on all aspects of growing grapes, help you visualize the process.

Grapes are produced from buds that will grow into shoots on 1-year old canes (the long stems or “shoots” after they’ve borne fruit for at least one year). The most fruitful canes will be those that were exposed to light during the growing season. These are thicker than a pencil in width and as close to the trunk as possible, Strik explained.

There are two types of grape pruning – cane pruning and spur pruning. Mature plants should be pruned yearly to remove all growth except new 1-year-old fruiting canes and renewal spurs (a cane pruned back to one to five buds).

To cane prune, select two to four new fruiting canes per vine. Cut back each of these to leave about 15 buds per cane. For wine grapes, leave about 20 to 30 buds per plant. In table grapes, leave 50 to 80 buds per plant. Leave a one- or two-bud spur cane near the fruiting cane with one or two buds each. These “renewal spurs” will produce the fruiting canes for the following year and thus maintain fruiting close to the trunk. All other cane growth should be pruned off.

Most table grapes produce the highest yield of good quality fruit when cane-pruned.

To spur prune, prune along main canes to leave two- to three- bud spurs, each four to six inches apart. Leave no more than 20 to 80 buds per plant, depending on the type of grape. Remove all other 1-year-old wood.

“If you prune properly, your vine will be more manageable and have better fruit,” Strik said. “Poor pruning year after year leads to low yield and poor fruit quality.”

UConn Home & Garden Education Center

Grapes: Pruning Techniques

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Pruning is one of the most important cultural operations in grape production because it regulates both vegetative growth and fruit production.
To properly prune a vine, you should know something about its growth and fruiting habit. The following image shows the major parts of a dormant vine after being pruned. This vine has been trained to the four-arm Kniffin system, one of several training systems used.
Pruning Terminology

The vines should be pruned during the dormant season, pre­ferably in March. Some things you must keep in mind are:

  • The fruit is borne on shoots rising from one-year-old wood.

  • The most productive canes are about pencil thickness (0.25-inch to 0.30-inch) and have an internodal length of five to eight inches between the fifth and sixth nodes or buds.

  • The most productive buds are in the mid-portion of the cane; therefore, it is best to leave canes of 8 to 16 buds in length. Thin canes should carry fewer buds than thicker canes.

  • To keep the fruiting wood close to the main trunk, leave one or two renewal spurs on or near each arm. (Cut back to short spurs leaving one to four buds).

  • Prune the vine so you will maintain a balance between vegetative growth and fruit production. Where a vine is under pruned, (too many buds left) the vine will produce many small clusters of small grapes that may fail to ripen properly. If the vine is over pruned, (too few buds left) the yield will be low and the vegetative growth excessive. To “balance prune” a vine, the number of buds left is adjusted according to the amount of one-year-old wood removed in pruning.

Methods of pruning and training:
There are two basic systems of pruning. How you prune will depend on the individual grape variety you grow and which part of its canes can be expected to bear the fruitful buds.
Cane Pruning
Commonly used for the Concord and other American varieties, is best suited to vines whose canes are most fruitful at a considerable distance from the base. On these vines, fairly long canes are left for fruiting wood and only the wood that is retained for renewal is cut back short.

  • Select the best-placed canes for renewal and cut them back to 2 buds each.

  • Select the best-quality canes for fruiting.

  • Decide how many buds the whole vine should bear.

  • Cut back the fruiting canes according to their vigor and size, and that of the vine.

  • Remove the rest of the wood.

  • Tie the vine to the trellis wire.

Spur Pruning
This method is more successful for most French hybrids since most of these varieties bear their most fruitful buds near the base of the canes. On these vines, all wood is spur-pruned, or cut back to the short spurs for both renewal and fruit production.

  • Select the best-placed, most fruitful canes.

  • Decide how many buds the whole vine should bear.

  • Cut enough canes back to 2-bud spurs.

  • Remove the rest of the wood.

  • Tie the vine to the trellis wire.

When to prune
Pruning is done during the winter, while the plant is dormant. The later in the dormant season that you prune, the later new growth will begin in the spring. Temperatures as low as -10° to -15° F may result in injury to the wood and buds of most grape varieties. In cold weather the frozen wood is brittle and easily broken: therefore it is advisable not to prune until late winter or early spring. When pruning is done late in the dormant season, the canes may “bleed” or drip sap from the cut ends. This is harmful to the vines.
Summer pruning or pruning while the vine is in a green or growing state can severely weaken its development. The green parts of the plant, its leaves, manufacture its food supply. Once removed, some of the food needed for growth is also removed. If any disbudding, removal of watersprouts, or suckering is needed, complete it early enough in the growing season that it will not injure the vine. Under no circumstances should growing shoots be cut back or any other green parts of the plant be removed.
The best guide for determining how many buds to leave for fruiting is a measure of the past year’s growth. Count the number of buds left the prior year and examine the canes that grew from those buds for diameter, length, and quality.

  • If the canes are at or near the best size and quality for fruiting wood leave the same number of buds.

  • If the canes are small too many buds were left last year. Reduce the number in this year’s pruning.

  • If the canes are larger than optimum or show excessive vigor of “bull” canes leave more buds than were previously left on the vine.

  • If you are not sure how many buds to retain it is better to prune more severely than to underprune. Leave fewer buds especially if the vine is a weak grower. If the vine has been very vigorous retain more buds.

Apparent vigor is not always a true indication of capacity under certain conditions. For example, young blossoms may be destroyed by a late frost, insects, or disease. When this happens, the shoots have increased vigor but not because the vine was under pruned. Do not leave more buds in this case.
Keep in mind the size of the crop produced the previous year and always balance the number of buds on each cane or spur with the vigor of the cane selected for fruiting.
For pesticide information or other questions please call toll free: 877-486-6271.
Revised by UConn Home and Garden Education Center 2016.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, the Dean of the College, Cooperative Extension System, University of Connecticut, Storrs. The Connecticut Cooperative Extension System is an equal opportunity employer and program provider. To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, Stop Code 9410, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964.

Dormant Spur and Cane Pruning Bunch Grapevines

Figure 10. Anvil (top left relative to large shears) and bypass (bottom left and right relative to large shears) hand shears are used to cut 1-year-old grapevine wood. Large shears (“loppers”, in center) are used to cut through grapevine wood that is older than 2 years old.

Summary

This bulletin was intended to provide both veteran and new growers an overview of commercially popular pruning strategies and a greater depth of understanding of the theory behind pruning method practice. Dormant pruning is an important vineyard management decision as it sets the crop level and canopy density before green tissues are present. Growers must take several considerations into account when choosing a pruning method, including vineyard design, cultivar, and labor force throughout the year. Some growers may choose to adopt several different pruning strategies to successfully manage their vineyard. Regardless of the pruning method, it is important to develop a plan that includes scheduling when and how each vineyard block will be pruned throughout the dormant season. Effective dormant pruning sets the stage for successful vineyard management throughout the forthcoming growing season.

Status and Revision History
Published on Dec 31, 2018

Optimized Pruning Using Spurs on Cordon Trained Grapevines

Wineries have come to expect and depend on delivery of high quality grapes from their growers, while at the same time, vineyard operational costs have reached new highs. Most wine grape growers have responded to these factors, striving for both production consistency and efficiency. Pruning is a vineyard management practice essential to both.

Through pruning, growers select buds for channeling annual grapevine growth into foliage. In effect, pruning integrates the affects of vineyard site, vineyard design, and past vineyard management on seasonal, above ground grapevine growth. In so doing, it sets the stage for fruit production at the beginning of each growing season.

Figure 1: One-bud spur

At the same time, pruning governs the partitioning of seasonal growth between vegetative growth (stems and leaves) and reproductive growth (clusters). It does so through bud number. Retaining more buds increases cluster growth relative to stem and leaf growth, while leaving fewer buds achieves the opposite effect.

Due to these portioning effects, pruning is a powerful tool for achieving growth balance, which is discernable as 14 to 20 leaves per shoot with two clusters. Growth balance promotes both consistent grape quality and operational efficiency. When a vine has too few buds, vines produce excessive leaf and stem growth and too few clusters. In this undercropped state, fruit and cane wood quality is diminished and fungal disease susceptibility increased. The reverse condition, with too many buds, results in too many clusters and too few leaves to support them. For such overcropped vines, fruit and wood ripening are impaired, tolerance for stresses is limited, and in severe cases, vine growth capacity and health declines.

Pruning also influences the positions of shoots in space through bud placement. Retaining more buds within a specific length of vine row increases shoot density, while leaving fewer buds has the reverse effect. Under most circumstances, a shoot density of 5 to 6 shoots per foot of cordon is best. A shoot density in this range facilitates the exposure of most leaves to direct sunlight, exposure of clusters to dappled sunlight, and the canopy interior to air movement. Due to its affect on shoot density, careful pruning is crucial for optimizing the configuration of canopies and the microclimates within them. Simultaneously, it facilitates vineyard operations, such as shoot thinning, spraying, and hedging. All of these influences contribute to production consistency and efficiency.

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This article is a revision of the Mid Valley Agricultural Services January 2002 Viticulture Newsletter.

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Over the years, interest in cane and machine pruning has gone through cycles, while spur pruning remains the wine grape industry standard. Actually, of the common pruning methods, spur pruning most readily lends itself to fruit production consistency and efficiency. It does so in part because it is associated with cordon training and the large reservoirs for nutrient storage cordons provide. But just as important, spur pruning provides precise control of bud number, spacing, and to some degree, orientation.

One-bud spur pruning is the most expeditious method to attain 5 to 6 shoots per foot of cordon. A 1-bud spur has one bud with a partial internode below that is at least a finger width (3/4 inch) (fig. 1). Buds at the base of spurs are normally not counted as they are sometimes less fruitful than buds above a semblance of an internode.

Figure 2: Excessive spur creep

The method, quite simply, involves retaining 1-bud spurs spaced 3 to 4 inches apart along a cordon. When shoots are 4 to 10 inches long, thinning to one shoot per spur conserves the desired shoot density. In the process, removing the shortest and longest shoots promotes uniformity among shoots. Also, while pruning each year, selecting the lowest cane of acceptable diameter (> 1/4 inch) arising from the previous years spur for this years spur minimizes spur creep and arm extension (fig. 2). These actions help to maintain fine form, promote consistency in fruit yields and quality, and maximize vineyard operational efficiency.

Where cordons form a single line in the vine row, as with a VSP or T trellis, the combination of 1-bud spur pruning and conservation shoot thinning yield about 3 to 6 tons per acre. While such yields are fine for high value grapes, they are insufficient for many California vineyards. Keeping fruitful basal shoots increases yields, but also increases shoot density. In these situations, allow some shoots to drape away from the center of the canopy and out into the middle in “ballerina” fashion to maintain optimum exposure. Alternatively, remove leaves from the fruit zone, which at least enhances cluster exposure.

Horizontally divided trellises are better solutions for realizing high yields with 1-bud spurs and conservation shoot thinning. With little or no remedial measures, these systems typically yield 7 to 12 tons per acre.

Figure 3: Well spaced 2-bud spurs

Two-bud spur pruning is the method used in many older vineyards. For them, with their well established spur positions, 1-bud spur pruning is usually not an option. Still, the basic principals presented above apply. The lower of the two buds on each spur still needs a semblance of an internode below it. The ideal shoot density remains 5 to 6 per foot of cordon, which equates to about 2 or 3 2-bud spurs per foot of cordon in combination with shoot thinning to conserve the density set at pruning (fig. 3). Where shoot densities must be higher to support larger crops, shoot positioning, leaf removal, or canopy division remain remedies for minimizing shading and the loss of production consistency and efficiency.

To summarize, pruning has effects of fundamental importance in wine grape production. It simultaneously channels vine resources into foliage growth, partitions shoot growth between clusters and leaves, and positions and orients emerging shoots. Pruning sets the stage for production each growing season, but has affects that carry over into the next. As such, it is a determinant of both fruit production consistency and efficiency.

Further reading

Pruning Grapevines

By Mary Bernard, Master Gardener

Pruning of grapevines in the home garden should be performed during the dormant season – from January through March 1. Many home grape growers prune their vines too lightly. Proper pruning modifies the size and form of the vine, making it a better producer of high quality, good-size fruit. Pruning also aids in balancing vegetative growth and fruit production.
Mature vines should be pruned yearly to remove all growth except new one-year old fruiting canes and/or renewal spurs. Clusters are produced on shoots that grow from buds on one-year old canes.
Grapes should be spur pruned or cane pruned. Most grape varieties are spur-pruned. The dormant shoots from the previous summer’s growth are selected and spaced along the vines’ cordon at 6 to 8 inch intervals. Select shoots that grew upward in a well-lighted environment for fruitful spurs. Shoots that grew in the shade the previous summer often do not contain fruitful buds. Prune back to several buds and remove all extra shoots. Short spurs (2 buds) should be left on fruitful varieties such as Cardinal, Exotic, Ribier, and Muscat of Alexandria. Long spurs (3 buds) are sometimes used for moderately fruitful varieties such as Concord, Golden Muscat, Catawba, and Niagara.
To cane prune, select two to four new fruiting canes per vine. Again, canes which developed on the top of the vine and which were exposed to light during the growing season will have buds that are more fruitful. You should retain the well-matured round canes with a diameter of 3/8 to 5/8 inch. Leave about 20 to 30 buds per plant for wine grapes and 50 to 80 buds per plant for table grapes, such as Thompson Seedless. Remove all other one-year old wood.
University of California Cooperative Extension Master Gardener Volunteers can provide additional gardening information upon request .Call the San Luis Obispo office at 781-5939 on Mondays and Thursdays from 1 to 5 PM. You may also call the Paso Robles office at 237-3100 on Wednesdays from 9 AM to 12 PM. The San Luis Obispo Master Gardeners website is at http://groups.ucanr.org/slomg/. Questions can be e-mailed to: [email protected]

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