Grapevines are very hardy and have lower water needs than most fruit-bearing plants. Although specific watering needs depend on the grape variety, soil type, and time of year, a good rule of thumb for grapes is to water the soil they’re planted in down to a depth of 12 inches once per week. When growing table grapes, water consistently from budding until harvest. If you’re growing wine grapes, you should reduce watering when the grapes begin to turn purple, for optimal flavor.
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How Often Do You Water a Grape Vine?
In locations with summer rain showers, the answer may be that you hardly have to water your grapes at all. Grape vines thrive with as little as 1 inch of rainfall every 10 days. Of course, drought conditions, lack of sun, and underwatering will reduce the amount of fruit the vines produce, so you’ll want to supplement any dry periods with weekly watering.
Plan to water once weekly, saturating the soil down to 12 inches in a 3-by-3 foot area at the base of each vine. This is the ideal depth to allow water to reach the grape vine rootstock. Because different soils absorb water better or worse than others, you may need to perform a soil watering test to determine how long to water to make sure you moisten the soil down to 12 inches. To perform a soil watering test, do the following:
- Arrange your drip line or soaker hose in a bare patch of ground.
- Water the ground for 5 minutes.
- Turn off the water and wait 2 hours.
- Dig into the watered ground and determine how deep the water reached.
- Now, time for some math. For example, if your soil is moist 2 inches below the surface after 5 minutes of watering, it would take 10 minutes of watering to reach a depth of 4 inches, 15 to reach a depth of 6 inches, and so on. In this example, watering soil to 12 inches will require 30 minutes of watering.
Once you know how quickly and deeply your soil absorbs water, you can use that as a guide for your watering schedule.
How Many Gallons of Water Does a Grape Vine Need?
The water needs for grape vines depend on the location. In temperate regions, such as the midwest and northeast, grape vines do well with as little as 5 gallons of water each week. In arid zones, such as Central California or Eastern Washington, grapes may require as much as 8–10 gallons of water each week to produce the highest quantity and quality of fruit.
Drip Irrigation for Grape Vines
Drip irrigation and soaker hoses are the best watering methods for grape vines. These methods not only conserve water by getting moisture right to the soil, they also keep grape vines healthier. Grapes are very susceptible to fungal rots that attack leaves. Overhead watering creates the perfect conditions for the most common and harmful grape diseases.
The best method for watering grapes is to arrange looped soaker hoses or an array of drip lines so that they soak a 3-by-3 foot area at the base of each vine.
Signs of Overwatering Grape Vines
Grapes are much more susceptible to harm from overwatering than they are to drought. Overwatering can cause root rot and several other diseases that can kill your grapes.
If the leaves of your grapes are yellowing, or if the tips of the leaves turn brown, these are sure signs the plant is suffering from overwatering. Additionally, if the soil is perpetually moist, that can be detrimental to grapes. Grapes thrive in sandy soil that soaks quickly and dries quickly. To replicate these conditions if your soil is moist, reduce watering frequency. Try watering once every 10 days instead of once per week.
Signs of Underwatering Grape Vines
While grape vines are hardy and drought-resistant, underwatering can force plants to drop leaves and fruit, and in some cases can be deadly. If the leaves of your grape vines are dry and beginning to curl, this is a sign that they aren’t getting enough water.
If your grapes stop growing during the growing season (they stop sending out new tendrils and leaves) this is another sign that the plants are suffering from water deprivation. If this occurs, increase your watering cadence slowly until you begin to see new growth. First, try watering once every 5 days instead of once per week.
Watering Wine Grapes for Best Results
Unlike table grapes, which should be watered regularly up until harvest, wine grapes actually benefit from a little underwatering at the right time. This produces the best flavor in your wine.
While the method varies by wine varietal, the generally accepted method is to reduce watering by about half at the time the grapes reach their final stage of ripening (when they begin to turn purple). So, if you’re watering your wine grapes weekly throughout the growing season, reduce the watering to once every 10–12 days during this lead-up to harvest. It’s the traditional method of many top winemakers.
Water Grapes Even After Harvest
While we plant grapes for the fruit they bear, it’s important to care for the vines to ensure the best harvest year after year. Following harvest, continue to water your grapes, slowly reducing watering as they naturally go into dormancy and drop their leaves. Once the leaves have fallen, you can cease watering until spring.
By continuing to water grapes up until they enter dormancy, you promote the overall health and growth of your vines. This means a strong return in spring and more fruit next year.
Proper Watering of Grapes
While watering needs for grapes varies based on grape variety, local environment, and time of year, a general rule is to water a 3-by-3 foot section of soil at the base of each grape vine once each week. Make sure to soak the soil down to 12 inches during each watering session. In dry regions, your watering cadence may have to be increased to twice per week, while in areas with more natural rainfall, watering should be reduced to prevent root rot and other grape diseases.