I've found most flowers turn into full-size fruit in 15 to 20 days, which means those little tomatoes are going to take another 15 to 20 days before they ripen. And that's given the optimal conditions for ripening.
You should see yellow flowers on your tomato plants at 5–7 weeks, and soon after that, you should see some of those flowers turning into little green tomatoes. If you don't get flowers, you will never get fruit!
Generally speaking, the common reason for tomato plants to only flower but not produce fruit is due to insufficient nutrition. Whether it's insufficient sunlight or soil fertility, it ultimately causes the plants to be malnourished and unable to produce fruit. Of course, there may be other reasons as well.
Tomatoes don't like their roots dry, so it's best to water them every day, they will also benefit from a weekly dose of liquid fertilizer.
Overwatering generally makes the plant look almost like it's rotting, as in drooping and turning soggy brown. My guess is it is having Nitrogen problems. Any type of vegetable fertilizer you buy at the store should work fine.
However many days it takes for the flower to turn into a green fruit, that is how many days it's going to take for this fruit to completely ripen. I've found most flowers turn into full-size fruit in 15 to 20 days, which means those little tomatoes are going to take another 15 to 20 days before they ripen.
Seed saved from a hybrid variety or from cross-pollination will not always grow true to type. While all heirloom varieties are open-pollinated, not all open pollinated varieties are heirlooms!
Tomatoes are prone to magnesium deficiency later in the growing season, which can show with yellowing leaves and diminished production. Ultra Epsom Salt treatments at the beginning of their planting and throughout their seasonal life can help to prevent and remedy magnesium deficiency in your tomato plants.
Insufficient sunlight
Without proper sunlight, the tomato plant will have leggy and spindly growth and little or no fruits. To produce tomatoes the plant requires energy which they receive from sunlight. Therefore, place your plant where it will receive enough sunlight to produce juicy and plumpy tomatoes.
If you have trouble with tomato plants not setting fruit, heat is likely to blame. Keep plants healthy to ride through the heat wave, and help prevent this problem by growing heat-set varieties. A soaker hose helps prevent diseases caused by overhead watering.
Some gardeners recommend you “pinch off” the flowers on your tomato transplants during their first weeks of growth, claiming that removing early blossoms: Directs more energy into establishing a strong root system. Results in a larger, sturdier, and potentially healthier tomato plant.
Fruit Formation (2-3 Weeks)
Once pollination occurs, bell peppers begin to develop. It takes approximately 2-3 weeks for the small, green peppers to form and start growing.
Tomatoes, squash, peppers, cucumbers, and other vegetables (and herbs!) will thrive when they're fed every 7 to 14 days with Miracle-Gro® Water Soluble Plant Food for Vegetables & Herbs.
A tomato plant has clustersof little yellow flowers. Each yellow flower contains a pistil (the female sexual organ) and stamens (the male sexual organs). So a tomato plant has both male and female reproductive organs in its flowers. To get tomatoes, the yellow flowers have to be pollinated.
Most cucumber varieties are monoecious with unisexual flowers—have separate male and female flowers within the same individual— and thus require animal pollination for reproduction. However, some varieties are mostly or totally gynoecious (produce only female flowers) and can produce fruit through parthenocarpy.
If your tomato plants are not setting fruit after blooms, it could be due to high temperatures, low temperatures, or insufficient pollination. Ensuring the plants are properly pollinated, using heat-tolerant varieties, and ensuring night temperatures stay within an ideal range can help set fruit.
2. Breaker Stage. In the Breaker Stage, color will be visible at the blossom-end of the tomato skin and tomatoes are considered to be “vine ripe." The color change at the blossom end indicates the tomato is producing ethylene, a ripening agent produced by the plant.
Water correctly: Do not overwater. The first week tomato plants are in the ground, they need water every day, but back off watering after the first week, slowly weaning the plants down to 1 to 1.5 inches of water per week.
Tomatoes thrive in loamy soils with good drainage and high organic matter content. Adding composted coffee grounds to planting beds is a great way to build healthy soil for tomato planting but won't provide all the required nutrients.
Also the lower leaves tend to get powdery mildew so it is good to remove them to stop disease spreading.