A mature grapevine can yield enough grapes to make a gallon of finished wine. In order to reach optimum grape production for wines, juices or eating fresh, some consideration must be given to location, weather and varietal distinctives.
Assessing Vineyard Location
Soils that drain well are a necessity and grapes will perform poorly or even die if planted in badly drained, wet areas. Because grapes send down deep roots, soil depth should be between 30 inches (76 cm) and as much as 70 inches (118 cm) before reaching hardpans or bedrock.
Vines do not produce high quality grapes in rich, highly organic soils, They prefer poor soils and when planted in too vigorous a soil will want to grow only leaves and little fruit.
Vines prefer sloping land. Slopes are usually well-drained and low in organic matter. Cool night air slides downhill and pools in the lowest place. Vines planted about three quarters of the way up the slope will have the cool air move down and away from the vineyard.
Trees too close to the vineyard have a negative impact on grape quality. Cool, moist air flows into the vineyard from under the trees during the day and from the tree crowns at night.
How Weather Affects Grapevines
When deciding on a grape variety be acquainted with the climate conditions in the vineyard. The length of the growing season can be a limiting factor as some grape varieties need a long growing season for grapes to ripen. Still-green grapes and a killing frost may mean no harvest.
Frost is also a consideration in late spring when vines have already budded. In areas that suffer spring frost injury, pruning vines to fewer, longer canes delays budbreak in the lower canes. Covering the vines with an insulating horticultural fabric can provide as much as 10 degrees of frost protection, usually sufficient to survive a late spring frost.
Excessive heat during the growing season slows vine growth as the plants attempt to conserve water. High heat during ripening can also hurt fruit quality.
During the summer vines prefer relatively dry conditions with infrequent watering. If too much rain falls in autumn, the vine's roots take up the water and transfer it to the grapes diluting flavors, sugars and acidity. Prolonged rain can cause rot.
Very windy sites may break canes during the growing season and winter winds can be dehydrating. Choose sites that are sheltered from prevailing winds or provide windbreaks. Dense plantings of shrubs, stone walls, terraces and snow fencing will mitigate the influence of strong winds.
Grape Varieties for the Vineyard
The best varieties to choose are those most adapted to the climate where they will be grown. All grape varieites grow and produce grapes where the climate is hot and sunny during the day with cooler nights and a long growing season. However, grapes ripening under hot conditions do not usually make good wines. For that reason very late-ripening varieites are the best choice.
Diseases are a concern where days are hot and humid and nights warm and dewy. Choose varieties that ripen late, produce loose clusters and have thicker skins, making them more rot resistant.
On sites that receive regular rainfall and morning dew during the entire growing and harvest season, with warms days and nights, the best choices are varieties that ripen mid-season and are resistant to bunch rots.
If winter temperatures typically dip to -15F (-26C), cold hardiness and early ripening are important qualities to look for in a variety. For extremely cold winter temperatures, Valiant has proven to be very winter hardy with survival reported where winter temperatures plunge to -50F (-50C).
Taking these factors into account before choosing grape varieties will increase the success of the vineyard.
Related articles:
Resource:
The Backyard Vintner by Jim Law, Quarry Books, 2005
 |
 |
 |
 |
