Like all angiosperms, tomatoes bloom and depend on insects to carry pollen from stamen to pistil to fertilize an egg so that it will grow and produce seed. The tomato is just a tasty seed carrier. The little yellow blossoms on a tomato plant are the key to its ability to reproduce; if there were no flowers on the plant, there will be no tomatoes. Disease cannot keep an angiosperm from blooming; the reasons would have more to do with culture.
Although wild tomatoes were perennials, their range was in temperate regions of Latin America, where winter freezes were rare. As tomatoes were "domesticated," they were taken to Europe, where they were grown as annuals and the little vine with the branches of berries became a part of the vegetable garden, yielding large, sweet fruit. The acceptance of the tomato as a food led to hybridization of varieties useful for cooking, preserving and eating by people who grew them wherever there were a few months of summer to grow them.
Tomato blooms are the sexual organs of the plants. Lack of bloom is a developmental flaw and therefore its cause must lie in the environment in which the plant has been kept. Tomatoes grow from seed that germinates when soil temperature reaches 60 degrees and when water and sunlight is available. This happens on a different date in each climate area or "growing zone."
Many gardeners start seeds or buy plants from garden centers and keep them indoors until the weather is settled. When plants are put out before the ground temperature is 60 degrees, the shock may stunt flower production. The plant will not bloom before it overcomes the shock and soil and air temperatures allow it to resume maturation.
Like any plant, tomatoes need nutrients. Of the three nutrients in most fertilizers, nitrogen, the "N" in the N-P-K formula on the label, encourages only rapid foliage growth. Phosphorus (P) and potassium (K) are essential to inflorescence, or blossoming. When a plant gets too much nitrogen, it keeps growing foliage; it cannot infloresce until nitrogen levels subside.
Tomatoes need full sun and warm days to bloom. Any time that they receive less than eight hours of sunlight or temperatures fall below 50, they will probably stop blooming. Shady porches or indoor gardens don't have enough sunlight for these vigorous growers.
Tomatoes need cool nights and warm days to set fruit. Nighttime temperatures below 50 degrees will delay blooming. By the same token, nighttime temperatures over 70 degrees during midsummer may cause plants to stop blooming. In both cases, plants should start blooming when nighttime temperatures settle reliably between 55 and 70 degrees.