Watering Tomatoes

National Gardening Association Editors

Tomatoes require an even supply of water throughout the season; an irregular water supply will cause your tomatoes to develop problems.

Give Them An Inch

Like most other vegetables in the garden, tomatoes need at least one inch of rain or irrigation water per week for steady growth. In the hotter, drier parts of the country, their needs go up to two inches of water per week during the summer months.

An inch of water measures out to about 60 gallons for each 100 square feet of garden. So, if you have to water by the bucket brigade, that's something to bear in mind.

Watering Technique

Here's a clever way of watering tomatoes. Cut the tops from some gallon-size cans, punch holes in the bottoms and set them in the ground with only about an inch of the can showing above the surface. Use two cans near each tomato plant and fill them two or three times per week -- or more often, if needed. This method directs water right to the root zone of the plants and little is wasted.

You can develop your own watering techniques as long as you follow these guidelines:

• Water thoroughly to encourage the tomato roots to seek water and nutrients deep in the soil. With an extensive, deep root system, the plants will hold up better during dry spells. When watering, soak the soil to a depth of at least six to eight inches.
• Water only when your plants need it. Tomatoes like moisture, but overwatering is harmful. You not only waste water, but soggy soil will prevent the roots from getting the air they need. If your plants look a little wilted on a hot, summer afternoon, that's usually normal. They'll perk up overnight. If plants are wilted in the morning, don't wait -- water them! (Certain diseases can also cause wilting.) A thorough soaking every four to five days on light, sandy soils and every seven to ten days on heavy soils is a good general guide for irrigating if you don't get enough rain.
• Water early in the day to cut down on evaporation losses and also to give your plants plenty of time to dry out. Wet foliage overnight may help trigger some diseases. With furrow irrigation, drip irrigation or soaker hoses, which all deliver water right at the soil surface and not on the leaves, you can water almost anytime. Try to avoid watering at midday though, because that's when evaporation losses are highest.
• Use a good mulch to help retain moisture in the soil. Mulches reduce the fluctuation of soil moisture and that helps the crop enormously. But, remember, don't apply mulch until after the transplants have been going for five to six weeks.