Growing tomatoes is a fascinating experience. It is easy to watch the progression of Solanum lycopersicum from seeds to seedlings throughout the growing season to full-grown plants that are ready to be harvested. Bright yellow flowers give way to fruit, as is ripens before your eyes.
When you grow tomatoes in your garden, the plants go through the same growth stages, regardless of whether you plant cherry, better boy, or paste tomatoes. To help you grow and produce a bountiful crop, it is helpful to understand each stage.
How Many Days to Maturity?
The time it takes to grow depends upon the variety planted and the fruit’s final size. “Days to maturity” is the length of time from when young plants are put in the soil until maturation. Since most seeds are started indoors, it is not counted from when you first sow the seeds.
- Early season varieties require 50 to 60 days to reach maturity.
- Mid-season varieties require 60 to 80 days to reach maturity.
- Late season varieties require more than 80 days to reach maturity.
Tomato Life Cycle
Its life cycle consists of the leaf, flower, and fruiting stages, each with specific growth habits and development needs. Stems and leaves grow during the leaf stage, needing nitrogen to fuel growth. Flowers and fruits require less nitrogen and higher potassium and phosphorus levels for good fruit production, development, and growth.
Tomatoes are annual plants, completing every stage of their growth — from a germinating seed to a plant with fruit containing seed — in one season.
In most United States growing zones, seeds are started indoors to allow germination, and seedlings are transplanted outside into the garden soil after the last spring frost threat. For seeds to grow, night temperatures need to stay consistently above 50℉; day temperatures should be such the garden soil remains above 60℉.
Spring Plantings: Start seeds indoors in early spring, approximately 6 to 8 weeks before the last frost date. Seeds are sown in a container or seed trays with potting mix.
Fall Plantings: Directly sow seeds into the soil sometime mid to late August, when temperatures are high, to speed seed germination. Tomatoes grow during the cool weather of the fall.
Once you plant seeds, keep the soil moist at all times. Seeds capable of germinating contain both an embryo and food reserves inside the protective seed coat to nourish initial growth. Through a process known as imbibition, soil moisture softens the seed coat and allows soil moisture to enter the seed. Once water penetrates the seed, it triggers internal cells to begin respiration and metabolizing the food reserves. The seed then germinates.
After sowing your seeds, expect germination in about five to ten days, which is quicker than average for most garden vegetable plants. The first step in germination is the emergence of the radicle or primary root. The radicle anchors the seedlings in the soil and then absorbs soil moisture and nutrients to facilitate the next growth stages.
Soon after the radicle begins absorbing moisture and nutrients, cells form an initial shoot. The shoot emerges from the seed and naturally grows upward, working its way towards the sunlight. Within a couple of days, the shoot breaks through the soil surface. Now the plant starts directing its energy and resources toward the development of leaves.
First True Leaf Forms
During this stage, young seedlings grow relatively slow. The seedling has limited resources to draw from, relying upon internal food reserves for metabolic processes. With these stores quickly dwindling, the tomato plant works hard to form leaves and start photosynthesis. At this time, the first true leaf appears, photosynthesis initiates, and the seedling starts producing food.
Third True Leaf Forms
Hormones inside the seedling work together, directing newly formed cells to develop new leaves rapidly. Growth picks up at a remarkably rapid pace; each new set of leaves formed increases the plant’s ability to photosynthesize. The third set of true leaves forms on the seedlings, looking like miniature versions of the mature foliage.
Root System Develops
Now that young seedlings have leaves capable of photosynthesizing and producing food, their root systems develop. An extensive root system develops to support the vegetable’s weight and absorb greater soil moisture and nutrients. The radicle elongates into a taproot, and a fibrous network of smaller roots forms as it continues to grow.
Vegetative Development Continues
At this point, the root system is adequately developed, and above foliage is producing food through photosynthesis. With these basics complete, the tomato plant switches to the vegetative phase of development. Focus changes to foliage’s upward and outward growth, and the vegetable starts setting aside resources for flowering in internal storage vacuoles.
When the tomato has 10 to 13 leaves and reaches between 12 and 18 inches tall, it starts developing new side stems. These side stems fork and branch out further, with flower buds forming along their tips. Once fully formed, the buds open, displaying characteristic yellow flowers, and the plant is ready for pollination.
The flowers on tomato plants contain both male and female reproductive parts, so the flowers self-pollinate without needing help from bees. Wind and external vibration of the flowers causes the heavy, sticky pollen grains to dislodge from the male parts, falling to the female reproductive organs, and fertilization begins. Immediately after fertilization, the fruit set occurs.
After pollination, fruit grows over the next 45 to 70 days, remaining green until it reaches its mature size. The amount of time it takes depends upon each cultivars, the local climate, and specific growing conditions. Since indeterminate varieties continue growing, remove new branches and stems to direct resources to the fruit and main stems.
Once tomatoes reach their mature size, ethylene — a gaseous hormone within each plant — triggers the fruit pigment to change, and ripening begins. Ripening happens through three developmental stages: breaker, pink, and red. Determinate varieties ripen all of the fruit at once; indeterminate varieties ripen fruit throughout the growing season, extending the crop harvest.
- Breaker: Slight stains of red appear on the fruit’s skin.
- Pink: Red stains enlarge, and as a result, the entire fruit turns pinks. It isn’t ready for consumption yet.
- Red: Pink “blush” deepens to the fruit’s ultimate red coloration, and it’s time to harvest.
As the ripening stage concludes and harvest occurs, the tomato prepares to complete its growing season. During the ripening stage, the ethylene in the vegetable also inhibits leaf senescence. Since seeds were already formed, the life cycle is finished. Growth hormones induce the genes responsible for senescence, and the plant dies.