Gardening: Soil preparation vital to growing grapevines

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Did you know that Pennsylvania is one of the country's top grape producers?

The vineyard titans of California have little to fear, however. While Pennsylvania certainly has its share of fine local wineries, the bulk of the commonwealth's production consists of Concord grapes, which are used for commercial nonalcoholic grape juice. Pennsylvania's cold winters pose a challenge for temperamental wine grapes, but fortunately for the home grower, table and jam grapes are not so demanding. Pennsylvania's climate is conducive to growing a number of grapevines that will be a welcome addition to any home garden.

To flourish, grapevines need a support such as an arbor, a fence or a trellis. Their flexible, woody stems cling to the support by tendrils and, with some effort, can be pruned in limitless ways.

The prerequisite for growing grapes in this region is to choose a variety that can withstand our icy winters. A stalwart native such as 'Concord,' 'Niagara' or 'Catawba' is a fine choice, but a number of hybrid or European varieties can flourish as well.

Historically, native American grapes (Vitis labrusca) were disdained for their distinctive "foxy" flavors, while European grapevines (Vitis vinifera) proved too delicate for frigid North American winters. Enter Konstantin Frank, a native of Ukraine who emigrated in 1951 and devoted his career to the cultivation of European grape varieties in the chilly Finger Lakes region of New York. Frank discovered that by grafting European vines onto native American root stock, the resulting plant would be hardy enough to survive the winter, yet would offer the more refined taste of its Old World ancestor. Frank's approach had the happy side effect of inoculating the European cuttings against the root louse Phylloxera, which is prevalent in American soils.

As a result, the home grower can choose French-American hybrids such as 'Chambourcin,' 'Vidal Blanc' and 'Vignoles' and classic Old World varieties such as 'Chardonnay' and 'Cabernet Sauvignon.'

Native varieties, which are extremely hardy, tolerant of cold and resistant to pests and diseases, still predominate in Pennsylvania's commercial vineyards. But newer plantings tend to feature the Old World varieties championed by Frank. If you are determined to plant a non-native vine, pay close attention to USDA hardiness zones. Generally, vinifera are hardy only to zero degrees Fahrenheit, and French American hybrids are hardy to 5 below zero Fahrenheit. Non-natives benefit from a minimum of 160 frost-free days per year.

The gardener's job begins the year before planting, with careful attention to site selection and soil preparation. Grapevines adore a maximum amount of sunlight, good air circulation, and deep well-drained soil. Shallow unamended soils do not drain well, and damp roots can lead to an array of fungal diseases. This explains why many commercial vineyards are found on hilltops and slopes, preferably with a southern or eastern exposure. A slope will maximize the vines' exposure to sunlight, and good air flow will allow foliage to dry out more quickly from rain and dew, further minimizing damage from fungal diseases.

Test the soil with a kit available from the Penn State Cooperative Extension, specifying grapes as your desired crop, and follow the instructions to the letter. Prior to planting, clear the space of weeds, vegetation and debris.

Most grape vines are sold as bare-root dormant plants, which should be planted in the spring as soon as the soil is workable. Prune off any dead roots and plant the vine in a large hole with the roots 4-6 inches below the soil surface. Vines should be spaced no closer than 3 feet from each other. If using a grafted variety, make sure the graft point is about 2 inches above the soil surface. Prune the plant down to one or two canes with two to three buds, or nodes, per cane.

Water and weed diligently during the first year. A few weeks after planting, apply 2 ounces of 33-0-0 fertilizer at a distance of a foot from the vine base. Test the soil every three to five years and amend accordingly. Keeping the ground beneath the vines raked and weed-free will help to protect the vine against the host of pests and diseases to which grapes are prone. Also, prune out any dead wood, leaves and fruit.

Grapevines take awhile to become established, but eventually the vine will produce much more wood than it can support. For this reason, vintners will prune out up to 90 percent of the new growth each year during the dormant season. One to two layers of leaves on the vine are ideal for grape production, as this permits adequate photosynthesis while allowing sufficient sunlight to reach the developing fruit. Do not remove all new growth, however, as grapevines bear fruit on 1-year-old wood.

By taking the time to choose a grape variety suited to our climate, and preparing for its maximum vigor and health, home gardeners can enjoy delicious grapes from their own backyards. The structure chosen to support grapes can be utilitarian or, with some time and imagination, can add vertical interest to the garden. A well-tended grapevine can bear fruit for up to 50 years. Why not make its presence a beautiful focal point in the garden?

garden

Kate DeSimone is a Penn State master gardener. Columns by master gardeners sometimes appear in place of the Garden Q&A by Sandy Feather, a Penn State Extension educator. First Published October 18, 2013 8:00 PM


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