Though quintessential plants in home gardens in any climate that will support them, tomatoes can be persnickety to grow. Water, nutrition, and temperature must be in the correct amounts at the correct time or an entire crop can be lost. Tomatoes require consistent watering throughout their main growing season, or else fruits can split, develop blossom-end rot, or the whole plant may just give up and die.
There is confusion over how much water a tomato plant needs at what time. Throughout its short life, these requirements change, which is the root of the confusion. When tomato plants are young and just setting blooms and first fruits, they need regular, thorough waterings. Soaking to a depth of 8 to 10 inches once a week is ideal. As the end of summer approaches, however, withhold water to spur fruits to ripen more quickly.
Mulches help tomatoes to retain the deep waterings you're giving them, if applied at the right time. As summer begins to get hot and dry, usually in July and August, apply a leaf or wheat straw mulch around the base of the plant, at least 1 inch deep. This helps to conserve water on hot summer days.
Cracked Tomato Fruits
Cracked fruits result from irregular watering. Sudden heavy rains in late spring can cause these developing fruits to burst when they are suddenly overwhelmed with available water. Thorough, regular watering and mulching can help keep water in the soil and prevent the tomato plants from being overwhelmed by too much water at one time.
Perhaps the most enigmatic of tomato problems, blossom-end rot results when a tomato receives too little calcium from the soil around it. One of the causes of this situation is irregular availability of water. Blossom-end rot first appears as a dark spot on the blossom end of the developing fruit, but quickly turns in to a large black, leathery spot, often colonized by molds. Regular watering and mulching can help to prevent this problem.