How Often and How Much to Water Tomato Plants?

Knowing when and how often to water your plants can sometimes feel more like an art than a science, perhaps no more so than for tomatoes. Overwatering tomatoes can lead to yellow and spotted leaves, while underwatering results in wilt and diseased fruit.

So how much and how often should you water your tomatoes? The University of Minnesota Extension offers helpful guidance to the science – and art – of watering tomatoes.

• Consistency is key to a successful watering practice for tomatoes, especially during fruit production. When the soil is allowed to dry out and then become oversaturated, the fruit can develop blossom-end rot.
• Soak the soil completely, for the best-tasting fruits.  Light watering keeps the water from seeping deep into the soil. When water remains nearer to the surface, the roots will stay there too, stressing the plant in hot, dry weather.
• Water the soil, not the leaves of your tomato plants. While Nature rains down on your plants from above, you should not.  Wet leaves, especially those splashed with soil, are at risk for disease.

• Knowing your type of soil is key to gauging its water content. If your soil is heavy clay, an inch of water will feel wet down to about six inches. Very sandy soil will feel wet down to about 10 inches from an inch of water. As a result, tomatoes in sandy soil tend to need more water than plants grown in heavier earth.
• When watering, use a trowel to see the depth of the water. If the trowel is only wet an inch or two, continue to water the plant.

Finally, a note on watering container-grown tomatoes. A patio or deck plant can be a great option for a tomato lover with limited space. Those plants, however, have a limited amount of soil from which to draw water, so they need a more frequent supply.

Container tomatoes should be watered at least once a day in summer. If the temperatures are high, water both morning and evening, using the trowel method to determine the depth of your water. 

And remember, all containers for plants should have holes to allow excess water to escape.  If an abundance of rain makes to soil boggy, give it time to dry out before you resume your watering plan.

– Written by Donna Lovell, Master Gardener