Grapes are a popular choice for the home garden. You can use the fruit in many ways, and properly managed grapevines are great additions to the home landscape. Though grapes can be grown throughout Oregon, they are considered temperate zone plants, requiring a cool winter to meet chilling requirements and a warm growing season (150 to 180 frost-free days) to develop and mature a crop.

Not all cultivars (varieties) are suited to a specific region. If the growing season is too short for a particular cultivar, the fruit may be of poor quality and low in sugar content at harvest. Also, the vines may not mature properly in the fall, leading to possible winter injury. In the cooler climate of the coast and the Willamette Valley, avoid choosing late-ripening cultivars. In eastern Oregon, choose only cold hardy cultivars and manage vines to reduce risk of winter cold injury (see “Choosing a cultivar”).

Along with choosing a site and cultivar, you should also consider site preparation, planting, general planting management, pruning and training, harvesting, and pest management.

In many ways, grapevines are easy to grow, but you need to give the vines very good care to produce high-quality fruit. The hardest parts of grape production are pruning and training. To prune well and properly, you must have an understanding of grape growth.

How grape plants grow

Here is an explanation of terms used to describe parts of the grape plant or its growth.

Cane. A mature shoot after harvest and leaf fall; a shoot becomes a cane after the growing season.

Cordon. An extension of the trunk, usually trained along a wire, from which spurs grow.

Fruiting zone. The section of a shoot where fruit clusters appear.

Head. The top of the trunk where it transitions to cordon, spurs, or canes.

Internode. Portion of the shoot or cane between two nodes.

Lateral. A branch of a shoot or cane.

Node. (1) Thickened portion of the shoot where the leaf and lateral bud appear; (2) the place on a cane or spur where a bud appears.

Shoot. New green growth with leaves, tendrils, and often flower clusters, developing from a bud on a cane or spur.

Spur. A cane pruned back to one to five buds. A spur is on a cordon or at the head of the vine.

Sucker. Also called a “water sprout”; a shoot growing from old wood, often at the trunk base or at the head of the vine.

Veraison. The start of grape ripening, when color change begins. Green berries start changing to red or blue in a colored grape cultivar, or a green grape becomes more translucent. In the Willamette Valley, this change occurs in about mid-August.

A dormant grapevine is illustrated in figure 1a. In the spring, shoots grow from buds on canes, renewal spurs (if present), and sometimes the trunk. Each bud on a cane or spur may produce from one to three shoots. As the shoot grows, it can produce leaves, flower clusters, buds, and lateral branches (figure 1b and figure 2). Fruit is produced on the current season’s growth.

When the vine is dormant once again (generally from December through March), you must prune it. The buds that produce next year’s fruit are on the 1-year-old canes (last year’s growth). To prevent the vine from producing too much fruit (overbearing), you must prune to keep only some of the 1-year-old wood or canes and remove the rest. Overbearing delays fruit ripening, reduces fruit quality, and weakens the vine.

Establishing the planting

Grapevines require several years from time of planting to first harvested crop, and they normally do not reach full production until the fifth or sixth year. Grape plants live for 50 to 100 years, if you care for them properly.

Choosing a site

The first step toward consistent production of high-quality grapes is to choose a sunny place to plant. While some ornamental grapevine species perform adequately in partial shade, full sunlight is required to get good production of table grapes. If you plant a row that runs north–south, the fruit and leaves will be better exposed to sunlight than in east–west rows; this way, you’ll produce better quality fruit.

Grapes can be grown on a wide range of soil types and soil nutrient status (for example, soil acidity or pH). European grapes may grow better than American types on soils with a pH greater than 7 (see “Choosing a cultivar”). Grapevines may have nutritional problems when grown on soils with a pH greater than 8.

Grape plants grow best in well-drained soils. Heavy clay soils with poor drainage or soils with an impervious subsoil clay pan are not ideal. Building up raised beds may improve growth on these soils.

When selecting a site, avoid areas prone to early spring frosts. New shoot growth in April and May is very susceptible to frost injury (see “Pests and problems”). Home surroundings or other sites that are sheltered from colder temperatures and wind are best. If possible, choose a sloping area, especially a south or southwest slope, because it generally has higher temperatures and is less likely to get frost.

Vines that are stressed due to drought or shade are more prone to diseases such as powdery mildew or botrytis fruit rot (see “Pests and problems”).

Choosing a cultivar

There are many grape cultivars available. You’ll find descriptions of cultivars in the table “Characteristics of table grape cultivars grown in Oregon”.

Local climate or growing conditions greatly influence a cultivar’s performance. Be sure to choose a cultivar that is adapted to your region. Regions differ in minimum winter cold temperature, but also in summer temperature or growing degree days (GDD) (table 1). Some cultivars, such as Niagara and Concord, require at least 2,000 GDD to ripen fully. Canadice, Interlaken, Reliance, and many other early to mid-season cultivars require 1,500 to 2,000 GDD to ripen fruit. If you live in cooler regions, such as the Oregon coast and parts of the Willamette Valley, choose only early to mid-season cultivars. Late-season cultivars may not fully ripen their fruit every year in these regions, though this can be influenced by pruning (see “Pruning”).

It’s important to consider a cultivar’s disease and cold tolerance (see “Pests and problems”). Tolerance to winter cold temperatures involves the health of the vine, yield the previous season, how well the vine became dormant, how quickly the temperature gets cold and how long it stays cold, and other factors. Dormant buds may be damaged at one temperature and trunks at another temperature. See the table “Characteristics of table grape cultivars grown in Oregon” for comments on cold hardiness of cultivars.

Because grapes are self-fertile, you need only one cultivar for fruit production. But, for variety and to extend the fruiting season, you may choose to grow several very early, mid-, or late-season ripening cultivars (depending on your climate).

Three types of grapes are grown in the Pacific Northwest: American, European, and European-American hybrids. Each has specific qualities.

• American cultivars (Vitis labrusca) have a strong “foxy” flavor and aroma (characteristic of Concord, the most common cultivar used for purple grape juice). Fruit generally have a slip-skin (pulp separates from the skin when you pop the berry in your mouth). American cultivars that have a slip-skin are noted in the table “Characteristics of table grape cultivars grown in Oregon”. The cluster can vary from tight to loose and berries from small to large, depending on cultivar.

Plants tend to be more tolerant of pests and more vigorous than the European type. This type of grape is tolerant or resistant to phylloxera, and it is more disease-resistant and cold hardy than the other types. These cultivars are used mostly for juice, jellies, pies, and fresh eating.

• European cultivars (Vitis vinifera) differ from American cultivars in fruit characteristics, vine growth habit, and climate adaptation. They have tight clusters, berries with thin skins that do not “slip,” and a more subtle aroma and flavor. Some cultivars have berries with a “crunchy” texture. In general, European grape cultivars are more sensitive to pests (such as phylloxera) and diseases (such as powdery mildew and botrytis bunch rot) and are less cold hardy than American types. For these reasons, European-type table grapes are not as commonly grown in home gardens in Oregon.

• European-American hybrids have some characteristics of both American and European types, depending on parentage.

Cultivars in the table “Characteristics of table grape cultivars grown in Oregon” are designated as European (E) or American (A). Hybrids are indicated as “A” with flavor and other attributes noted. See the graphics “Photographs of cultivars, by color” for photos of some cultivars.

Cultivars differ in ripening time, characterized by season as “very early“ to “late.” Note that cultural practices (such as pruning) and weather can influence harvest time. In the Willamette Valley, very early season cultivars would be ready for fruit harvest in early September. Late-season cultivars, such as Concord, may not be ripe until mid-October when pruned well.

Yield per vine varies tremendously with vine age, site (climate, depth of soil, soil fertility), management (pruning, irrigation, plant fertility, pest management), and cultivar. Yield per plant, for a mature, well-managed vine, may be from 15 to 35 pounds.

Spacing

Spacing within the row depends on the cultivar you plant, the depth or fertility of your soil, and the training system you use (see “Training,” ). Plant European cultivars (Vitis vinifera) 6 feet apart in the row. You can set American cultivars (V. labrusca) and hybrids 6 to 8 feet apart in the row, because they are more vigorous (produce longer shoots). If your soil is shallow or of low fertility, you can space vines closer together in the row to “fill” the trellis.

The spacing between rows depends, in part, on the training and trellis system you choose. In backyard plantings, 9 to 10 feet between rows is common for single canopy training systems (head trained, single downward hanging canopy, vertical hedgerow or VSP, and Scott Henry). If you plan to train to a Geneva Double Curtain (GDC) and will have more than one row of vines, use a between-row spacing of 11 to 12 feet.

Preparing the soil

Be sure soil is free of perennial weeds and well tilled before you plant. You can improve the organic matter content of heavy soil by incorporating well-aged sawdust, manure, or compost.

Don’t place manure or compost directly in the planting hole. Instead, incorporate it into soil in the whole planting area. Apply organic matter the summer or fall before you plant. Manure applied at 2 to 3 cubic yards per 100 square feet is a good source. Use only materials that you believe are free from insects and weed seeds. Dig, plow, or till the material into the soil to ensure that it will be well decomposed by planting time.

If you incorporate large amounts of non-decomposed material into the soil, add calcium nitrate (16 percent nitrogen) or equivalent fertilizer at 2 pounds of product per 100 square feet to aid in decomposition. If you also use manure to improve soil structure, decrease the rate of fertilizer by half.

Planting

Plant grapes in early spring, as soon as you can work the soil.

At planting, prune off all broken roots and trim very long roots. Set plants in a hole large enough to spread roots without bending them. For plants growing in a pot, remove the pot (whether it’s fiber or plastic) and place the rootball into a sufficiently large hole. Plant all bare-root or potted plants at the same depth that they were growing in the nursery.

Firm the soil well around roots to remove air pockets, and water thoroughly. Continue to irrigate plants as required to keep soil adequately moist without saturating it.

Right after planting, prune off all but one vigorous 1-year-old cane from nursery-bought plants. Prune the cane back to two buds. On plants that are already growing, remove all but the most vigorously growing shoot near the base of the plant. This will become the new trunk.

Young grapevines can’t compete with weeds or established lawn grass for water and nutrients. Keep the planting free of all weeds in the establishment years. Cultivate shallowly, no deeper than 1 to 3 inches, to avoid injuring roots.

Grapevines can be planted through black plastic. The plastic mulch reduces weed growth and increases soil temperature (which may benefit root growth in western Oregon). Place the plastic down the row before planting. Cut holes in the plastic about 1 foot in diameter where you will plant the vines. The black plastic lasts 1 to 2 years. Be sure to dispose of it appropriately before it deteriorates too much.

Fertilizing and irrigating

In general, fertilize grapes sparingly. More problems occur from overfeeding than from underfeeding. In the planting year, fertilize each plant with a total of 0.5 to 1 ounce of nitrogen (N), depending on soil fertility. Use a well-balanced fertilizer such as 16-16-16. To calculate how much product to apply, divide the desired amount of N (in this case, 1 ounce) by the percentage of N in the fertilizer:

16% = 0.16

1 oz ÷ 0.16 = 6.3 oz product per plant

You also may use manure or compost.

In the second year, plants may be fertilized with 1 to 1.5 ounces of N per plant if needed. Broadcast the fertilizer in a circle about 6 to 18 inches from the trunk. Be careful not to get fertilizer right up against the trunk or to place it all in one spot near the vine. The best time to fertilize is around bud break.

Newly planted vines need proper watering to establish in any soil type. Keep the soil sufficiently moist without overwatering.

Training the young vine

The main goal of training the vine in the establishment year is to develop a well-established root system and a trunk. In the planting year, select the strongest shoot that grows from each newly planted vine and train it to a stake or twine that’s attached to the trellis wire, so that it develops a straight trunk. Prune off all other shoots before they grow longer than 12 inches so the vine can direct its growth to the new trunk (figure 4).

Sometimes the shoot won’t reach the training wire or desired head height in the first year. If this happens, prune it back the next winter to three or four buds. It may seem you’ve wasted a whole year’s growth, but the root system is considerably larger. Provided there is no adverse soil or pest condition, you should get much better trunk growth in the second year. In this case, train the strongest shoot that grows the following summer and prune off all others.

In colder regions, it is common just to grow a bush the first year and train the trunk in the second year. Also, you can train more than one trunk in cold regions to reduce the risk of losing the plant to cold injury (see “Pests and problems”).

Once the shoot reaches the wire or desired head height, do not top it during the growing season. Instead, wait until the vine is dormant. Cut it at a node (through a bud) about 3 to 4 inches above the desired height, and tie it to the wire (figure 5A).

Further training and pruning depend on the training system you choose (see “Training”). Once you choose the training system, you’ll build a trellis (see “Trellis”).

No fruit is produced in the planting year.

Maintaining the planting

Fertilizing and irrigating

Young, establishing vines or plants grown on soil of low fertility may benefit from annual applications of fertilizer, manure, or compost (to supply about 1 ounce of N per plant).

Irrigate vines, if necessary, to help the plants survive dry periods and mature their fruit. If vines grow so vigorously that they develop dense canopies, increased disease, and reduced fruit production, be sure to gradually decrease amounts of water in mid- to late summer.

Older vines grown on sandy soils (such as those found in central and eastern Oregon) require irrigation to ensure good plant growth and fruit production. Grapes grown on clay-loam soils in the Willamette Valley can be grown without irrigation. But in the Willamette Valley’s long, dry summers, it’s often helpful to give plants a small amount of irrigation during the latter stages of fruit ripening. This helps prevent berry splitting, which can happen late in the season after rainfall on unirrigated vines.

In coastal areas and the Willamette Valley, be sure not to over-irrigate a producing vine. Always irrigate fruiting vines under the canopy to lessen the development of disease.

Pruning

The framework of an established vine—the way it looks after pruning—varies depending on the training system you choose. The pruning instructions that follow are for a vine trained to a single downward hanging canopy. Other training systems are described in the section on “Training”.

Proper pruning and training are essential for producing a good yield of high-quality fruit and maintaining a balance between vegetative growth and fruiting. The most common problem in home garden grape production is that vines aren’t pruned hard enough. When you prune, you must remove most of the wood produced the previous season—prune off about 90 percent! Leave relatively little wood to produce the following season’s crop. If you prune properly, your vine will be more manageable and have better fruit. Poor pruning year after year leads to a low yield and poor fruit quality.

Prune vines when they’re dormant, from January through early March. If the vine bleeds sap from the cut portions, don’t worry: there is no evidence that this harms the vine.

There are two methods of pruning: cane pruning and spur pruning. Once you understand these methods, you’ll be able to prune a vine no matter what training system you use.

Some cultivars perform best when they are cane pruned, and others when they are spur pruned. The best pruning method to use (when known) is shown in the cultivar descriptions in the table “Characteristics of table grape cultivars grown in Oregon.” In general, European grapes may be cane or spur pruned. Other cultivars, especially American types and many hybrids, produce only vegetative shoots on the basal buds of canes. If these are pruned to short spurs, they produce little or no fruit. For this reason, it’s best to cane prune cultivars when no specific pruning method is recommended.

In cooler areas of the Willamette Valley or the coast, spur pruning can promote crowded shoots, thus increasing the risk of fruit rot. It may be an advantage to cane prune in these cooler regions.

Cane pruning

These instructions are for a single downward hanging canopy.

Second growing season

You’ve planted on a site with good fertility. At the end of the first growing season, you trained the vine to a stake or wire to attain the desired head height. You pruned the trunk the first winter (figure 5A).

In the second growing season, shoots develop from buds on the 1-year-old trunk. Retain two shoots that grow 2 to 6 inches below the training wire. Train these shoots, one on each side of the trunk, along the wire. These shoots become the fruiting canes for next year.

Remove all shoots, other than the two you selected, while they’re still small. You want the vine to direct its energy to the two shoots you want to keep. The vine is too young to produce any fruit, so prune off any clusters before or at bloom. Also, remove any suckers that develop at the base of the vine (figure 5B).

In the second winter, prune back the two canes to 7 to 10 buds each, depending on vigor (14 to 20 buds per plant, figure 5C). These buds would produce fruit, and it’s important not to let young vines overproduce.

Third growing season

Shoots grow from buds on tthe 1-year-old canes you left at pruning, and these shoots produce fruit (figure 5D). You may need to remove any extra shoots that develop from buds at the nodes (see “Shoot thinning”). If there is an average of more than one fruit cluster per shoot, prune off the extra clusters at bloom to prevent the young plant from overbearing (see “Fruit thinning”).

The grapevine in the third winter, before and after pruning, is illustrated in figures 5E and 5F. You must select new fruiting wood and remove the rest (about 90 percent) of the canes. When you choose fruiting canes, be aware that canes differ in fruitfulness.

The most fruitful canes are those that were exposed to light during the previous growing season, are at least pencil width in diameter, and have an average internode length for the cultivar. Long internodes indicate too much vigor, so poor fruiting is likely next year.

It’s best to keep the vine’s fruiting area as close to the trunk as possible. Choose two new, desirable fruiting canes (indicated by shading in figure 5E) that are close to the trunk. Cut back each cane to about 15 buds (or 30 per plant; figure 5F). Keep fewer buds on plants that are low in vigor. Wrap the canes loosely around the wire and tie at the end. It’s best to use flexible tie-tape rather than string or twist-ties that can girdle the vine.

You can leave a one- or two-bud spur near the head of the vine (figure 5F). These renewal spurs often supply new fruiting canes when you prune the following year, and they also help keep fruiting close to the trunk.

Years 4 through maturity

In the fourth fruiting season and after, you will not need to do any fruit thinning if you prune vines well. However, thinning to one shoot per node is recommended every year to keep an open canopy, which improves fruit quality and reduces disease (see “Shoot thinning”). Continue to remove suckers at the base of the trunk and the head of the vine during the growing season.

Prune plants yearly in the dormant period to remove all growth except new fruiting canes and renewal spurs. Choose a fruiting cane from each of the renewal spurs. If the canes from a renewal spur are undesirable for some reason, then choose a different cane that is close to the trunk (figure 5G).

Cut back each fruiting cane to control the number of buds per vine. The number of buds to leave depends on:

• Climate. Vines in cooler climates ripen less fruit and need fewer buds, particularly on late-season cultivars.

• Soil. Fertile soil increases vine vigor and the number of buds left at pruning.

• Vine age. Vines in years 4 and 5 can support fewer buds than those that are mature.

• Cultivar. American types can support more buds than European types.

In general, leave 20 to 60 buds per plant (or 10 to 25 buds per cane in this training example, figure 5H). Prune younger vines, in years 4 and 5, to the lower end of the range. You can adjust bud number at pruning up or down, with experience. If the vine is growing well and ripens its crop well, you can maintain or try slightly increasing bud number the following year.

When vines are grown in rows, mature vines are usually pruned without counting buds. Their cane is pruned to meet the cane from the adjacent vine with no overlap.

Spur pruning

Establishing a vine for spur pruning is the same as for cane pruning in the early years. Until the third winter, prune the young vine as illustrated in figures 5A through 5D for a vine trained to a single downward hanging canopy.

Third growing season (Figure 5D)

Remove any extra shoots that develop from buds at the nodes (see “Shoot thinning”). If there is an average of more than one fruit cluster per shoot, prune off the extra clusters at bloom to prevent the young plant from overbearing (see “Fruit thinning”).

In the third winter, cut back the selected canes (indicated by shading in figure 6A) along the older wood to two- or three-bud spurs. Spurs should be 4 to 6 inches apart. The 2-year-old cane that was trained to the wire the previous winter now becomes a “permanent” part of the vine, called the cordon. If more than one shoot grew from a node on the cordon (if you missed some when shoot thinning), choose the strongest one and cut off the others (figure 6B). Leave no more than about 30 buds per plant. If plants are low in vigor, leave fewer buds. Buds on spurs will produce fruit in cultivars that are adapted to this method of pruning.

Years 4 through maturity

In the fourth fruiting season and after, you will not need to do any fruit thinning if you prune vines well. However, thinning to one shoot per node is recommended every year to keep an open canopy, which improves fruit quality and reduces disease. Continue to remove suckers at the base of the trunk and the head of the vine during the growing season.

To prune mature plants, select new spurs (ideally those nearest the cordon), cut them back to two to six buds, depending on cultivar, and remove all other canes (figures 6C and 6D). In general, leave 20 to 60 buds per plant. However, the number of buds per plant depends on the same factors as for cane-pruned vines (climate, soil, vine age, and cultivar).

If you’re not sure whether a cultivar’s basal buds are fruitful and it’s suited for spur pruning, it’s best to cane prune the vine. It’s easy to convert from one system of pruning to the other, though. So, if you’re interested in spur pruning, try both methods on a particular cultivar and compare results.

Training

You can train grapevines in many ways. The training systems described below are well suited to all production regions in Oregon, unless otherwise noted.

Single downward hanging canopy

This system requires a simple trellis consisting of posts and a single wire at about 6 feet high. The trunk is trained to about 6 feet tall, and two canes are trained in opposite directions down the wire to meet the cane from the adjacent plant. Shoots are not trained between any wires during the growing season, but are left to “hang” downward. This system can be cane or spur pruned (figures 5D, 6C, 7, 8, and 9).

Geneva Double Curtain (GDC)

This system, developed in Geneva, New York, is well suited to vigorous American-type grapes that can be pruned to a relatively high number of buds. Vines are pruned to four fruiting canes or four cordons. It is generally best to use this training system on vigorous sites.

The trellis must be of sturdy construction to support the weight of vine growth and fruit production. The trunk must be trained to a high head height, about 5½ feet tall. A center wire at this height serves as the trunk’s training wire. The GDC requires cross-arms about 3 to 4 feet wide. Run a wire down the row on each side of the cross-arm or “T.” These become the cane training wires (figures 10 and 11).

Train the shoot (the future trunk) to head height in the first growing season. If growth is vigorous, train the shoot toward one side of the “T” and down a wire if needed. For these instructions, we will assume only a trunk, to head height, grew the first year.

In the second growing season, choose two shoots, one per side, to grow toward the cane training wires of the “T.” These become the arms, or permanent part of the vine that extends from the trunk to the cane training wires. Train these shoots down the wire as they grow (for example, toward the south). Remove all other shoots early in development.

In the third growing season, prune the existing canes (one per side on the south end of the vine) to limit fruit production. Choose one shoot on each cane, near the arm, to train down the wire toward the north. The following winter, select a new 1-year-old cane from the south side to become that side’s new fruiting cane. Prune it back to limit fruit production. On the north side, prune back the 1-year-old cane to limit the crop. Repeat this on the other side of the trellis.

The next winter, choose a new fruiting cane on each of the four sections of the vine (on each side of the arm). After pruning, the vine will have four fruiting canes (figure 10). This training system can also be spur pruned to four cordons.

During the growing and fruiting season, thin shoots to one shoot per node, if necessary (see “Shoot thinning”). Look at your vine frequently to make sure that shoots are hanging down in distinct curtains on each side of the trunk. It’s important for light to reach both sides of the curtain. If you do not manage shoots well, they intertwine, creating a 4-foot thick canopy. Fruit will not get enough light, which delays ripening and increases risk of disease.

Vertical hedgerow (also called 2-cane Guyot, VSP, or two-cane Kniffen)

In this system, the head height of the trunk varies from very short in cooler areas (1½ to 2 feet) to 3 feet in warmer regions. Vines are pruned to two canes or cordons (figure 12). The trellis requires a training wire at head height and two to three sets of training wires above head height to about 6 feet. Shoots produced from canes or spurs are trained upward between the sets of training wires on the trellis (figures 13 and 14). Keeping the shoots upright in a narrow canopy improves the fruit’s exposure to light. Many wine grapes are grown in Oregon using this method. Table grapes are more often grown using downward hanging systems.

Head training

In areas with limited space, it’s possible to train vines to a self-supporting trunk with no trellis. Young vine trunks are tied to a stake and become self-supporting as they grow (figures 15 and 16). Prune vines to long spurs that originate at the head of the vine (figure 17A). This method is inexpensive and requires less space, but yields are lower. A common mistake made in the home garden is to “hedge prune” these head-trained vines (figure 17B). This produces too many spurs, which leaves too many buds and—in American types—many spurs that are too short for good fruit production.

Arbors

Grapes are well suited to training on an arbor. The plants make attractive ornamentals and provide shade (figure 18). Depending on how the arbor is constructed, fruit hangs down through the arbor to see and harvest underneath.

You can choose a red-, blue-, and green-fruited grape to grow on each side of a large, three-sided arbor. If you grow one vine per side, plant each in the center of its arbor “wall” and train each trunk to grow up the side and along the top to the middle of the arbor. It may take more than 2 years to grow a trunk to that length.

After the first growing season (when the goal is to grow the trunk as tall as possible), select shoots along each trunk to distribute fruiting canes along the trunk’s length. If a trunk is not tall enough yet, use the topmost shoot to extend the trunk in the current season. Repeat this process until the framework of the vine has been established (each vine’s trunk goes up the side and along the top to the middle of the arbor). Have short fruiting canes alternate on the left and right sides of each trunk, so that shoots (leaves and shade) and fruit are well distributed along the trunk and arbor.

Scott Henry

This system of pruning vines to four canes and dividing the canopy was invented by Scott Henry, owner of a vineyard and winery near Roseburg, Oregon. The system is suited to European table grapes grown on a vigorous soil and can be spur pruned.

The trellis should have two cane-training wires, one at about 2½ feet from the ground and another at 3½ feet (figure 19). Train the trunk to a 2½-foot head height. Prune the vine to four canes. Allow the shoots from the two lower canes to grow downward; they are not “trained.” Train the shoots from the two upper canes upward and between catch wires (see “Vertical hedgerow,” 5; figure 20). Train four shoots near the head of the vine upward. These become the fruiting canes for next year.

It’s important not to let the upper shoots shade the lower ones, or quality will be relatively poor.

Four-cane Kniffen

Home garden grape books often refer to this system. It is similar to the Scott Henry, but shoots are not trained. The top shoots are allowed to shade the lower ones (figure 21). This system is not generally recommended for cool regions in Oregon. Also, it is best not to spur prune this system in western Oregon to avoid too much shading.

Trellis

A trellis is required for most training systems. Building a trellis is like building a fence: take care to make the trellis strong and brace it well. It needs to bear the weight of vigorously growing vines and a heavy crop.

It’s best to build the trellis in the first growing season, so that you can start training vines to the trellis early (rather than to a stake).

The type of trellis you need varies with the training system you use (see “Training”). However, all trellises have certain characteristics in common.

End posts should be strong, about 8 to 9 feet long, and have a diameter of at least 6 inches. Treated wooden posts are best, though you can use concrete or large steel posts. Set end posts about 2 to 3 feet deep and leaning slightly away from the center of the row. For most training systems, 6 feet of post should be above ground. To brace the end posts, use large screw anchors or an “H” brace (figures 22 and 23).

Line posts are those in the row between the end posts. Space them 18 to 21 feet apart (or every three plants) and set them 2 feet deep. Wooden line posts should have a minimum diameter of 3 inches. An option for some training systems (like the single downward hanging canopy) is to place a steel fence post at each plant.

Use high-tensile, 12-gauge or heavier wire. Insert a wire tightener (e.g., figure 24) in each head- or cane-training wire. Wires must be tightened each winter after pruning.

To make moveable training wires, add chain-link to the end of wires at the row ends (figure 23) and put nails or hooks in the post. This allows you to move wires as you train the shoots. The number of wires you need depends on the training system you use.

Summer pruning

There are several pruning techniques you can use in spring and summer to manage the vine for good fruit quality.

Shoot thinning

In spring, a grapevine can produce up to three shoots per bud at a node. When you prune to a certain number of buds per vine, you are estimating yield by assuming there will be only one fruitful shoot per node. Shoot thinning is removing extra shoots to leave just one shoot per node. Thin shoots once in spring when the main shoot is about 6 inches long. You can usually determine the shoot to keep because it’s longer than the secondary or tertiary shoots (shorter shoots at the same node). Remove the extra shoot(s) by carefully snapping them off (figure 25 A–D). Avoid shoot thinning when shoots are too long, so you won’t accidentally remove the main (primary) shoot.

Fruit thinning

It’s best to limit young vines to one cluster per shoot (see “Pruning”). This is called fruit thinning. Thin fruit right before bloom to improve fruit set on the remaining clusters.

Fruit thinning can also be done later in the season, if you feel you haven’t pruned the vine severely enough and there’s too much fruit for the crop to ripen well. If you remove fruit clusters before veraison, berry size increases, yield is less affected, and the grape clusters ripen sooner. If you thin fruit soon after veraison, there is little effect on berry size, but yield is reduced, and the remaining fruit ripens sooner.

In general, shoots need to be at least 3 feet long to support a fruit crop. Remove clusters from shorter shoots.

Hedging

Usually, 3 to 4 feet of growth per shoot is enough to ripen a crop. If plants become too vigorous, you can top or trim shoots. Be sure not to shorten too much the shoots that are to become next year’s new fruiting canes. Hedged or tipped shoots produce lateral branches. Trim these also to prevent too much shading of the fruiting zone.

Leaf pulling

Good exposure to sun improves fruit quality. In cooler climates, you can remove two to four leaves per shoot in the fruiting zone so that clusters are less shaded. Remove leaves only on the side of the row that gets morning sun (figure 26). Do not remove leaves on the side that gets afternoon sun, or clusters may get sunburned. If you pull leaves off when fruit are pea-size (about late June) or earlier, the clusters won’t get sunburned.

Pruning an old, neglected vine

A common question home gardeners ask is whether they can “save” an old, neglected vine. Usually, they refer to a vine that wasn’t pruned or trained well to begin with, or one that hasn’t been pruned for many years. First of all, if the vine has sentimental value or you really like the variety and want to “save” it, it’s best to take some cuttings just in case the pruning methods described here don’t work (see “Propagation”).

A vine that hasn’t been managed well will have many small (short and thin) shoots. Often, these are at the growing ends of the plant—perhaps high up in a tree or on the roof of an old shed! This growth produces low-quality fruit, isn’t good material for cane or spur pruning, and isn’t in a place where you can harvest the fruit easily.

If the vine has a decent trunk and looks like it had a good framework in the past, you might be able to save it. Prune it heavily by removing most of the wood, leaving only about 40 buds on 1-year-old wood. This wood might still be high up in a tree, but it’s needed to support new shoot growth.

With such a severe pruning, the vine may produce new suckers at the head of the vine or at the base of the trunk. If this happens, you will have new shoots that will become your fruiting canes next winter. You can use a sucker to replace the trunk. In that case, you would remove the older wood (up in the tree, in this example) the winter following the severe pruning.

For a vine that has too many trunks to count and you don’t know where to begin pruning, try cutting the vine back to near ground level. Often, the vine will produce new suckers. (This method doesn’t work on grafted vines) Choose one of the new suckers to be your new trunk, and train it. The following winter, pile soil around this new trunk so that it will form its own roots (the old stump will rot out).

Remember: to be safe, be sure to take cuttings to propagate the vine in case the severe pruning doesn’t work.

Harvest

There are several signs that can help you judge the ripeness of your grapes.

• The color of ripe grapes varies with cultivar. Once you become familiar with a particular variety, color can help you judge when the grapes are getting close to maturity.

• The stem that supports the cluster changes from green to brown as the cluster reaches maturity.

• The seeds of seeded grapes darken as the berry matures.

The best way to judge whether table grapes are ripe is to taste them. Taste berries at the tip of the cluster. These are the last to ripen.

Grapes become sweeter and less acid as they mature. The characteristic aroma and flavor of a cultivar develops relatively late in the ripening process, with intensity increasing as the grapes “hang.” But, grapes also start to soften if they are left to hang too long, which decreases storage life. Also, the longer you let fruit hang on the vine in the fall, the greater the risk of damage from birds, bees, and fruit rot.

If you are an avid grower, you might buy a hand-held refractometer, a device that measures the percentage of soluble solids or sugar content (also known as “Brix”). These cost a little over $150.

As you decide when to harvest, you must consider the weather and its potential effects on fruit. Rain on mature fruit may cause shattering (falling from the cluster), cracking or splitting, and an increase in fruit rot.

The average temperature must be above 50°F for grapes to continue to mature on the vine. Grapes do not ripen further after they’ve been picked.

Use pruning shears to harvest clusters. Store clusters in the refrigerator in vented plastic bags.

Pests and problems

Environment

Winter cold injury

American grapes are the most cold hardy, while European grapes are the least. In the Willamette Valley and coastal areas of Oregon, cold damage to buds and canes of European grapes occurs rarely, and then only on the coolest sites (such as at high elevation). Cold injury to European table grapes and hybrids is more common in eastern-Oregon growing regions. There, these types of grapes may be grown using certain methods to train vines or protect them with soil or mulch during cold winter months. Refer to the publication Protecting Grapevines from Winter Injury (“For further reading”).

Frost

After bud break in spring, grapevine shoots are sensitive to frost damage. If frost injury occurs, there may be a less developed shoot or bud at that node that will grow and produce a partial crop.

To reduce risk of frost injury on cooler sites:

• Grow vines near compacted bare soil rather than near weeds or grass.

• Leave long canes when pruning, which delays bud break on the more basal part of the canes. Remove the extra cane length after risk of frost has passed.

• Keep other canes as “spare parts” to delay bud break. Remove the extra canes or buds after risk of frost has passed.

• Train to a high head height. Higher from the ground tends to be warmer during frost season.

Risk of frost injury varies a great deal among sites and even among locations on the same property. Cultivars may also differ in timing of bud break, which can make some cultivars more susceptible to frost.

Stunted spring growth

In spring, affected shoots have zig-zag internodes and are generally stunted. This can be caused by nutrient deficiencies (particularly zinc and boron), herbicide injury, spring frost damage, or mites. Refer to the publication Grapevine Growth Distortions (“For further reading”) for more information and suggested control measures.

Herbicide injury

Grapes are very sensitive to herbicide injury. Distorted leaves (figure 27) and shoot tips are common symptoms in areas where herbicide drift (particularly of a 2,4-D product) has occurred. Avoid using these herbicide products near grapes or on days when drift may occur (hot or windy conditions).

Pests

Phylloxera

This aphid-like insect feeds on roots, weakening the plant. Many American or hybrid table grape cultivars are tolerant of this pest, but European cultivars are susceptible. European wine grapes are available from nurseries as vines grafted to a resistant rootstock, but most European table grapes available in the Pacific Northwest are not grafted.

Phylloxera can kill a susceptible grapevine. There are no control measures for this pest if susceptible, non-grafted vines become infested.

Grape erineum mite

Mites feeding on leaves cause characteristic fuzzy spots on the underside of leaves (figure 28). There is no need to control this pest, as it doesn’t really harm the vine or the fruit.

Wasps and hornets

These insects feed on fruit before it’s considered fully ripe or ready for harvest. They use their mandibles to tear a hole in the berry skin and then eat out the fruit contents, leaving a hard shell. Use traps in the row to minimize these pests.

Birds

Birds can be major pests. Scare devices, such as aluminum plates or flagging, offer little control. The only sure method of protection is to place netting over the vines or along the fruiting zone.

Deer

Unfortunately, deer like eating grapevines. Adequate fencing is the only sure way to protect the vines.

Rodents

Voles and field mice damage vines by chewing on the cambium layer just under the bark. If vines are girdled, they die. Avoid tall grass or mulch around vine trunks. These encourage rodents.

Weeds

Mature vines may be able to compete with most weeds on fertile soil. In shallower soil or around young vines, use shallow cultivation to control weeds. You can use mulch, but mulch may become a home for mice or voles in winter, and they can girdle and kill the trunk.

Disease

Crown gall

This is a bacterial disease that causes a gall or enlarged area at a wound site, often the base of the vine. The bacterium is systemic in the plant, so cleaning your pruners between vines may help limit its spread.

Botrytis fruit rot

This disease is also called gray mold. Fruit rot is aggravated in cool, wet autumns, especially in dense canopies where fruit clusters stay moist longer. To minimize this disease, use cultural methods of canopy management (shoot thinning, leaf pulling, shoot positioning) to increase cluster exposure to sun and wind.

Powdery mildew

This disease affects both leaves and fruit. Leaves show yellow to brown patches on the leaf upper surface (figure 29A). Fruit shows a gray “netting” on the berry’s surface and splitting in severe infections (figure 29B). Fruit affected by powdery mildew has a bad off-flavor.

Cultivars differ considerably in their sensitivity to powdery mildew. In general, European cultivars are most susceptible and may require several applications of sulfur or other fungicides for control. Good canopy exposure and air circulation also help manage this disease.

For more information on pests, see the following publications (in “For further reading,” below).

• Pest Management Guide for Wine Grapes in Oregon

• Pacific Northwest Insect Management Handbook

• Pacific Northwest Plant Disease Management Handbook

• Pacific Northwest Weed Management Handbook

Also, check with your local OSU Extension Service office for management recommendations.

For further reading

Establishing a Vineyard in Oregon—A Quick Start Resource Guide (EM 8973-E). 2009. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20551/em8973-e.pdf

Grape Phylloxera—Biology and Management in the Pacific Northwest (EC 1463-E). 2009. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19539/ec1463-e.pdf

Grapevine Growth Distortions—A Guide to Identifying Symptoms (EM 8975-E). 2009. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20598/em8975-e.pdf

Pacific Northwest Pest Management Handbooks Insect Management Handbook. Plant Disease Management Handbook. Weed Management Handbook. Oregon State University Extension Service. http://pnwhandbooks.org/

Pest Management Guide for Wine Grapes In Oregon (EM 8413). 2011. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20097/em8413-2011.pdf

Preventing Herbicide Drift and Injury to Grapevines (EM 8860). 2004. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20353/em8860.pdf

Preventing Phenoxy Herbicide Damage to Grape Vineyards (EM 8737). 1999. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20090/em8737-e.pdf

Protecting Grapevines from Winter Injury (PNW 603-E). 2008. Oregon State University Extension Service. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20803/pnw603-e.pdf

The Grape Grower—A Guide to Organic Viticulture. 2002. Chelsea Green Pub. Co., White River Junction, VT. 289 pp.

© 2011 Oregon State University

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