The Art of Growing Grapes

What is one of the most widely grown fruits in the world that is rarely seen in home gardens? Grapes.

“The main reason that home growers have ignored grapes is that they are not very easy to grow,” says Mare-Anne Jarvela, senior editor of The Old Farmer's Almanac.

While growing grapes in your backyard may be more challenging than growing tomatoes, it’s not impossible. If you’re thinking about trying it, here are five things to know before you start digging, followed by a simple how-to section below.

Ensuring a Good Grape-Growing Environment

“Grapes need plenty of space in areas that get full sun with good drainage and air circulation to grow well,” says Jarvela. And don’t expect to plant them and be done with it. “It takes a lot of effort to grow grapes. Grapes need to be trellised and pruned every year.” In general, you’ll need 50 to 100 square feet of trellis or arbor space per vine. All grapes do best with a full day of sunlight. They can’t tolerate wet feet.

If you have the right growing conditions and are willing to make the effort that growing grapes requires, you can likely find a variety of grape suitable for the temperatures in your area. Grapes can be grown in USDA zones 2-10, which is to say almost anywhere in the continental United States.

Choosing the Right Variety

Before you rush out and buy grapevines, you’ll need to make an important decision that will determine what type of grapevine to purchase. What’s your goal? Do you want to grow grapes to eat or to make wine? Once you’ve answered this question, you’re ready to find a variety that will grow and produce well in your area.

There are several basic types of grapes:

• American (Vitis labrusca) grapes are the most cold-hardy. They include Concord and Niagara and are used mostly for juice and jelly.
• European (Vitis viniferia) grapes are grown as wine and table grapes and also for raisins. They prefer a warm and dry Mediterranean-type climate with a longer growing season.
• American hybrids are made from American and European species.
• Muscadine (Vitis rotundifolia), a North American native, has a thick skin and grows in the South.

Which variety grows well in your climate depends largely on how hot it gets in the summer and how cold in the winter. If you don’t know your temperature extremes, contact your local extension office. When you call, ask the agent for growing tips for your area, as well as variety recommendations.

Preparing the Planting Site

Grape roots grow deep, as much as 15 feet. Because most of those roots are in the top three feet, dig a planting hole about two feet deep and wide. While grapevines are adaptable to a wide range of soils, in general the plants prefer a soil rich in compost. “Don’t simply mix compost only in the planting hole, though,” says Chuck Ingels, who is the pomology, viticulture and environmental horticulture adviser at the University of California Cooperative Extension in Sacramento. And don’t simply dig a planting hole, especially in heavy clay soils, he advises. “Many people make the planting hole so rich that roots may not want to venture out beyond the hole,” Ingels adds. “Rototill compost into the soil in a larger area, such as about a 20 square foot area before digging the hole.” Also, he says, adding organic amendments deeply (e.g., 2 feet deep) to heavy soil may result in rotting and anaerobic breakdown, which is toxic to the roots.

Planting the Vines

The best time to plant grape vines is while the plants are dormant. This is from January to early spring, depending on where you live. It is also when you’ll find plants available from retail nurseries as bare-root, one-year-old vines. Because bare roots dry out quickly, plant the vine as soon as possible after bringing it home. The plant should have the original cane and some new canes emerging from it. Remove all of the new canes except the one that looks the strongest. Prune it back to two buds. After these buds send out new shoots, choose the strongest as the new trunk. The other cane should be cut back to just several inches. A shoot that grows from it then becomes a “reserve” trunk in case the first choice is damaged or broken.

In general, allow 50-100 square feet of support space per vine in home gardens.

Fertilizing Grapes

Grapes can adapt to a wide range of soils as long as the soil has good drainage. They also have few nutritional needs. Ask your local extension service about recommended fertilizer for your area and for the variety you have chosen. A general rule of thumb is to avoid using too much nitrogen. An excessive amount of nitrogen can cause heavy vegetative growth and poor fruit set or fruit that is of poor quality, as well as increased pest and disease problems.

Staving Off Birds and Diseases

“If you don’t use netting, birds will often eat the grapes before you can harvest them,” says Jarvela. You’ll also have to take steps to keep mold at bay. “Grapes often get mildew on the leaves or suffer from other fungal diseases.“

Powdery mildew is the most common disease affecting grapes, according to Ingels. Mildew is caused by a fungus and the spores can spread rapidly even when the weather is not wet and humid. Signs of the problem show up as yellow spots on the upper surface of leaves and as a white powdery appearance on fruit and cluster stems. During the winter, the previous season’s infections appear as red blotchy areas on the canes.

To prevent possible problems, Ingels suggests planting in as much sun as possible, avoiding over-watering or over-fertilizing with nitrogen, and careful pruning, including removal of shoots that don’t bear fruit, to improve air circulation. The standard method of control, he says, is to spray with wettable sulfur at seven- to 10-day intervals during the spring. He also says that horticultural oils can be used because they also control leafhoppers and other insects. However, he points out, wait a few weeks after applying sulfur to spray the oils. American juice varieties, such as Concord and Niabell, are resistant to powdery mildew, Ingels says.

Pruning Grape Vines

Assuming you have the proper location and have chosen a variety suited to your location, one of the most important things you can do to grow grapes that produce well is to adopt good pruning practices. When the grapes go dormant, prune off everything but a few stems and train them on the support system you have chosen. Don’t be bashful! You may be surprised by how much you trim — perhaps as much as 90 percent. The goal is to create enough one-year-old fruiting branches to produce a good fruit set but to keep the vegetation from being too dense.

Be aware, also, that when the vines start producing fruit they can make a lot of it. This may be the poster child for too much of a good thing. An overabundance of fruit can result in small fruit of inferior quality as well as stunting of the vines. “Another way to improve the size and quality of the fruit is to thin to one cluster per shoot, or on an arbor to about one cluster per one-two square feet,” Ingels advises. “The amount to thin depends on the size of the clusters and the vigor of the vine. The greater the shoot growth, the more clusters you leave. Stunted vines should be thinned more heavily. Then try to figure out why the vines aren’t growing enough. Also, table grapes (for eating) generally require more thinning to make the berries large. Wine grape berries can and should be smaller, but even wine grapes may require thinning.”

If you are not sure when the grapes are ripe, it’s OK to pick one (or two!) for a taste test!