The weather during the first two weeks of May this year was lovely – mild (warm, not hot) days and cool nights. Tomatoes have had the best start to the growing season I’ve seen in many years. The root systems of tomatoes that were planted in late April and early May (after a premature hot spell earlier in April) have developed quickly and flower set is excellent. Tomatoes that were planted in late March or April (before the hot spell) have mostly recovered from April’s heat stress followed by cooler than normal temperatures and also have good flower set; some have already set fruit.
Blossoms fall off when daytime temperatures are above 90 degrees and hormone fruit set sprays aren’t effective when temperatures are high. Make a note of the varieties that you’ve planted that tolerate hot weather best and replant the most successful types next year. Encourage fruit set by tapping the cages to release pollen from tomato flowers several times a week. Or, as one friend does, let the dog run around in the garden every day.
Fertilizers formulated for tomatoes will have lower nitrogen levels (the first number on the label) and higher phosphorus and potassium levels to promote flowering rather than foliage growth. They should also contain extra calcium, at least three to five per cent; extra calcium helps prevent blossom end rot when the bottom of the tomato turns gray and mushy. A tablespoon or two of bone meal or bulb food will also add extra calcium. Those fertilizers are worth the money (and can be used on all flowering plants) since the most common cause of poor flower and fruit set in tomatoes is too much nitrogen. Feed tomatoes by first irrigating the soil well, then lightly scratching in a half cup of a low nitrogen fertilizer and watering it in slowly.
The most important feeding for tomatoes is given when the plants first set fruit. Feed again every four to six weeks. Determinate or bush varieties (Ace, Roma) have a shorter growing season than indeterminate or vine type tomatoes (Better Boy, Champion, Early Girl).
Sunscald on tomatoes is a common problem here in the central San Joaquin Valley. Yellow, leathery patches develop on the sides of fruit overexposed to sunlight. “Full sun” means six hours a day of sunlight; tomatoes planted in our “full sun” or fourteen hours a day of intense rays in July often suffer from sunscald. Many gardeners pinch off new shoots growing in the axils or branch joints of tomato plants to encourage bigger fruit size. However, tomatoes growing in our sunny climate need the shade provided by the extra leaves on those shoots to help prevent sunscald.
There are two types of skin cracking on tomatoes. Circular cracking is caused by inconsistent watering. Irrigate tomatoes when the top two or three inches of soil is dry which might mean hand watering in summer on days not on the mandated schedule.
Cracks that radiate from the stem occur when temperatures are above ninety degrees or when fruit receives too much sunlight. Cracked tomatoes can be eaten safely; just cut out or around the cracks. Do the same with the bottom ends of tomatoes affected by blossom end rot and enjoy the fruits of your labor.
Elinor Teague: firstname.lastname@example.org