Whether you grow your tomatoes in pots or directly in the soil, adequate water promotes healthy, vigorous growth and plump, juicy fruit. These tender perennials, grown across much of the U.S. as annuals, require ample water as they are heavy feeders and wilt quickly when water is withheld. The amount of water required depends on the size of the plant, weather and the size of the pot. Keeping the soil evenly moist avoids unnecessary stress to plants in high temperatures.
Check drainage holes in the bottom of pots or containers used for growing tomatoes. Drill holes for drainage or place a layer of gravel or stones in the bottom to prevent roots from sitting in water. Although tomatoes prefer moist soil, pots that do not drain well create the prime conditions for disease and prevent young roots from receiving the oxygen needed to thrive.
Water when the soil is dry. For tomatoes grown in pots, daily watering may be necessary. The larger the plant grows, the more water it requires. Water until water flows through the holes in the bottom of the pot. Do not allow plants to sit in soggy soil.
Allow soil to dry slightly before watering again. Check the moisture content of the soil by sticking your finger into the soil to a depth of 3 to 4 inches. If the soil feels dry to the touch, water the plant.
Check tomato plants daily for signs of wilting. Water in the morning to prevent damage from sun scald on wet foliage. If watering must be done in the afternoon, water early enough so that foliage dries before sunset to prevent disease. Cool, damp conditions promote disease.