Stages of a Tomato Plant

Seed

• The seed is the dormant or resting stage of the plant life cycle. Each tomato seed weighs about 100 mg (3/1000 of an ounce) and remains viable for about 5 years. Seed packets give name of variety, planting depth, soil temperature for germination, plant spacing and number of days until harvest, and state whether the variety is determinate or indeterminate in growth habit.

Seedlings

• After seeds are planted in moistened soil, a series of metabolic reactions occur that break dormancy. Germination usually takes 6 to 10 days. Seed leaves (cotyledons) emerge first, followed by hairy leaves with serrated edges. While the seedling is unbranched, vigorous growth occurs underground. A taproot grows as much as 22 inches deep in 3 weeks. The taproot is usually broken during transplanting, and a fibrous root system develops. Supply strong light and brush the tops of plants twice a day with your hands to enhance seedling vigor.

Vegetative Growth Stage

• During the vegetative growth stage, the plant develops above and below ground, doubling in size every 12 to 15 days. The young vegetative plant starts to branch, often profusely. Determinate plants are usually smaller, with growth of each stem ending when flowers are produced. Indeterminate plants grow continuously because flowers are produced on side shoots. The popular hybrid Celebrity is called semi-determinate, producing just three to four main stems. Suckers, offshoots with roots, appear. Many home gardeners remove all suckers, top plants and thin dense foliage to curb excessive vegetative growth.

Flowering Stage

• The shift to flowering occurs when growing tips have excess sugars. Bright yellow, five-petalled flowers appear at the ends of stems in clusters called "trusses." Beefsteak tomato growers eliminate some of the flowers in a truss to prevent stems breaking from heavy fruit. Flowers shed pollen on sunny days between 10 a.m. and 4 p.m., depending on bumblebees and wind for transfer of pollen, containing sperm, from the male part (anther) to the female organ (pistil) of the same flower. Fertilization occurs when a pollen tube grows down through the pistil, carrying the sperm to an ovule (immature seed) in the ovary. Cold temperatures and low humidity interfere with fruit set. Each seed in a tomato fruit is the result of a fertilization event. Flowering continues until frost kills the plant.

Fruit-Ripening Stage

• After successful fruits set, flower petals wither. Young fruits begin as pea-sized orbs. Ripening from the blossom end, they undergo a series of color changes, from pale green to white to pink, and then red, orange, yellow or purplish black. The fruit matures about 45 to 50 days after fertilization. Seeds saved from open-pollinated (non-hybrid) varieties will produce progeny nearly identical to the parents. Store seeds in dark, dry, cool conditions.