The climate for growing grapes is generally one in which winters are fairly mild. Long, deep and frigid winters such as those in the very northern parts of the United States are generally unsuited for growing grapes. Similarly, very moist and humid conditions aren't conducive to grape growing either. The best is somewhere in the middle, within zones 5 through 7, although the micro climate, or climate in the immediate growing area, can be good for growing grapes. It all depends upon the area and the type of grapes you wish to grow.
Climate for Growing Grapes
The climate for growing grapes depends on both the maco and micro environment.
The macro climate is very important for growing grapes, but the micro climate is also important. The macro climate refers to the overall climate found in a large region. The growing or gardening zone may be considered the macro climate. The macro climate is determined by many factors, including the average cold temperatures in the winter and hot temperatures in the summer and the number of frost free, warm growing days all year long. In general, grapes need about 150 to 170 days with temperatures over 50 degrees Fahrenheit in order to grow, flower and set fruit.
The micro climate, on the other hand, may make one area better suited for growing grapes than another. Many vineyards are planted along the sloping hills of valleys or the slopes leading down to bodies of water such as lakes. The slopes offer proper drainage for grape vine roots, which is very important for their growth and development.
Yet slopes also offer the advantage of a micro climate that is slightly warmer than the surrounding area. Warm air settles in pockets along slopes and valleys and may make a small area slightly warmer than the surrounding countryside. While this may not be noticeable to the average person, plants notice it, and it gives the grapevines a climactic boost that makes grapes thrive in particular parts of the country. That's why the Great Lakes Region of New York, for example, is a great grape producing area, and other valleys in the United States and Europe are known for their fine grape production.
Other Factors for Successful Grape Production
In addition to the temperature, other factors positively influence grape growth and development. Because grapevines are prone to mildew and fungus, good air circulation is important. A windy area helps provide good air circulation around the leaves and prevents mildews. Adequate rainfall during the growing season is also important. While grapevines prefer rocky, sandy soil, they do need abundant water. Grapes like a soil pH of between 6 and 6.5, but can grow anywhere between a pH of 5 and 7. When in doubt, conduct a soil sample test and speak with a local County Cooperative Extension agent to see if amendments are needed.
Specific Climate Resources
Growing grapes successfully varies a lot from region to region. That's why many state horticultural groups and associations produce pamphlets and information specific for their region. Try some of the resources below, or contact your own state cooperative extension office for grape growing tips for your location.