While we all may regard a tomato as a vegetable, it truly is a fruit since it forms from a fertilized, ripening flower ovary. It takes 45 to 50 days for the tomato to grow from flower to harvest. Tomato plants enjoy heat and moist soil, producing fruits until the plants die from an autumn frost. Luckily, the seeds of the fruits store well once dried and will germinate next spring to create new plants to grow in the garden.
Appearing in clusters from the bases of leaves, warm temperatures and sunshine coax the five-petaled flowers to open along the youngest parts of the plant stems. Within each yellow flower are the sex organs, including the ovary at the base of the flower that is destined to become the tomato fruit.
Bees pollinate the flowers, brushing the male pollen onto the female pistil. Fertilization occurs when the pollen grains migrate through the pistil and enter the ovary at the base of the flower. Fertilization yields viable, fertile seeds and causes the flower petals to wither and the ovary to grow.
For two to three weeks, the ovary slowly enlarges, quickly swells to reach maturity, and changes to green after an additional three to five weeks. The skin of the fruit begins to blush from light green to the first hints of orange. Metabolic changes begin inside of the fruit, as cell walls turn soft and the tissues around the developed seeds turn more juicy and gel-like.
The outer skin of the fruit continues to deepen from orange and orange-red to the ripe color of blood red. The fruit also emits a fragrance. Bugs, birds and animals see or smell the fruit and eat the flesh, exposing the seeds. Some creatures digest the seeds and deposit them far from the mother plant. Fruits not damaged by insects or animals get so ripe that the stem dries and drops the fruit to the ground below.
With the fruit free from the mother plant and ridden with seeds, the fruit slowly degrades and decays, exposing the seeds to sunlight and air. Seeds may germinate immediately in contact with soil or they may rot inside the wet pulp if ambient humidity is high. Seeds that dry in the decaying body of the fruit remain dormant until conditions favor seed germination, which sometimes occurs many months later after winter cold passes and soil conditions become favorable.