Grape vines look elegant trailing up a trellis in your garden, and the fruit is good for jelly, wine or just eating fresh off the vine. Fruits like grapes require a good amount of water to make them plump and juicy, but too much water can cause the roots to rot. Many growers of wine grapes in Europe practice "dry farming" and do not water their grapes at all, while grape farmers in California water their grapes regularly. Finding the right balance of water for your grapes will help ensure a good grape harvest.
Water your grape vine thoroughly when you first plant it to help it become established, and then water once a week for the first month. Grape vines need more water during their first year than any other.
Examine the soil where your grapes are growing. Grapes don't like wet feet, and if the soil is naturally moist, you may not need to water at all.
Consider the variety of grape you are growing. Some varieties are more drought resistant than others, and will perform well with dry farming, while other varieties need regular watering. Often, tart grapes or wine grapes need less water than sweet, table grapes, although this is not a set rule. Let your grape vines dictate their water needs. If the leaves are wilting and the fruit is small, hard and dry, your grape vines may need more water.
Watch the weather. Grape vines are tenacious and can usually withstand hot, dry weather just fine. However, grapes grown in a desert region will need water more often than grapes in a temperate zone.
Water your grape vines deeply but infrequently to encourage strong root systems that dig deep into the earth. Use a drip irrigation system so that the water goes directly to the roots and does not evaporate into the air or collect on the leaves. If you're not sure if your grape vines need water, dig a hole with a shovel about two feet way from your grape vine and about two feet down. Squeeze a handful of soil between your palms. If the soil is moist and clumps into a ball, the grape vines was well hydrated. If the soil crumbles and is dry, you may need to water your grape vines.
Reduce watering after you have harvested the fruit, but don't allow the grape vine to dry out completely. The plant still needs water to produce roots and leaves.