Fruit of the Vine|
Grapes for winemaking are grown in many areas of the U.S., as well as other countries such as France, Chile and Australia. The major wine-producing area in the U.S. is California, which accounts for 80 to 90 percent of U.S. wine production. Many categories of winemaking grapes are grown throughout the country and include the following:
- Vitis Vinifera - European type, such as Chardonnay, Cabernet Sauvignon, Merlot, Sauvignon Blanc, Riesling
- French-American Hybrids - Baco Noir, Chambourcin, Seyval Blanc, Vidal Blanc, Villard Noir
- Vitis Labrusca - American-type grapes, such as Catawba, Concord, Delaware, Niagara
- Vitis Rotundifolia - native to North Carolina, such as Carlos, Magnolia, Scuppernog
Typically, the type of grape that is used to make the wine gives the wine its name, such as Chardonnay, Cabernet Sauvignon and Zinfandel. However, some wines are blends of various types of wines, such as a Semillon Chardonnay. The blending of various wines to produce a given flavor is part of the art of the winemaking.
Growing grapes, a process known as viticulture, involves a complex interaction (terroir) between the following factors:
- Soil - Soil influences how much water and heat are available. Grapes need a steady, but not excessive, water supply.
- Color - Dark soils tend to be warmer than light soils because they are better at absorbing and holding heat.
- Geology - Rocky or stony soils allow water to drain better than clay soils; rocks also help to absorb heat in the soil.
- Chemicals - The role of chemicals in the soil is not clearly understood (see sidebar).
- Topography - This influences the amount of sunlight available (temperature) and the drainage (water supply).
- Climate/Microclimate - This influences temperature, sunlight and water (rainfall, fog, mist). Some grapes, such as Vitis Vinifera, tend to grow best in areas where the seasonal temperature varies by about 30 to 35 degrees Fahrenheit (17 to 19 degrees Celsius).
The types of grapes that are planted and grown in any given area depend upon the terroir. In the Northern Hemisphere, grapes begin to bud in late March or early April. The grapes grow, bloom and develop fruit throughout the summer. The grower's goal is to keep the leaf growth small, which allows more sun in and keeps the grape clusters small yet numerous. The growers must also watch for signs of drought, disease and pests. In late September or early October, the grapes are ready to harvest. The actual times vary with the climate, latitude and judgment of individual growers.
Chemicals in the Soil
While the role of chemicals in the soil is not clearly understood, we do know that:
- Too much nitrogen yields heavy leaf growth and shade, while too little produces hydrogen sulfide.
- Too little potassium makes plants vulnerable to drought and disease and yields grapes that are low in sugar.
- pH is not critical, because grapes grow in a variety of soil pH levels.
- Too much organic material yields too much nitrogen and water, but too little will not support many soil organisms (earthworms).