- Tomato plants undergo five primary growth stages: germination, seedling, vegetative, flowering and fruiting.
- Each stage of the tomato life cycle requires different needs for sunlight, warmth, water and more.
- Fruit appears on a tomato plant during the fifth stage of growth.
As an avid home gardener, I have over 20 years of experience growing tomatoes and plant five or more varieties in my garden every summer. Over the years, I’ve learned that a productive tomato harvest doesn’t happen overnight and understanding the life cycle of a tomato plant helps maximize yield and minimize problems. From the moment a seed sprouts to the final juicy fruit, each phase plays a key role in a tomato’s development.
Here, I’ll walk you through the five main stages of a tomato plant’s growth, including what to expect at each phase and how to set your plant up for success. I also tapped Lucy Mercer, certified master gardener extension volunteer and founder of the cooking and gardening blog A Cook and Her Books, for expert advice.
1. Germination (Days 0–10)
The tomato plant’s journey begins when seeds are planted in warm, moist soil. During germination, the seeds absorb water, swell and split open to produce a tiny root (radicle) and a shoot (plumule). For best results, use fresh seeds from a reputable source. Start them in a sterile, soilless seed-starting mix placed in a tray with a humidity dome to maintain moisture. The ideal soil temperature is 70–80°F (21–27°C), as consistent warmth is essential for germination.
“When you use a heat mat to start your seedlings, you ensure consistent germination and reduce the likelihood of damping-off disease,” says Mercer. “The bonus is that heat makes the seeds germinate quicker.” Once the seeds sprout, remove the humidity dome to prevent excess moisture and reduce the risk of disease.
2. Seedling Stage (Days 10–25)
About 10 days after germination, tomato seedlings develop their first true leaves. These follow the cotyledons, the seed’s built-in food supply and the plant’s initial leaf-like structures. During this stage, roots grow deeper and the young plant starts to establish itself.
Ample light is critical for successful seedling development. Without it, seedlings may become leggy and weak. Seedlings require 14–16 hours of bright light daily. If using grow lights, position them one to two inches above the tops of the seedlings, adjusting them as needed as the seedlings grow to prevent stretching. If you’re not using a grow light, rotate the tray daily to encourage even, upright growth.
Air circulation is just as important for healthy development. “Fungal diseases can be devastating to your seed starting project,” warns Mercer. “They spread quickly and can destroy flats of seeds in no time. Set up a fan to keep air moving and help your plants grow strong and healthy.”
3. Vegetative Growth (Weeks 3–6+)
During the vegetative stage, tomato plants focus on growing bigger and stronger. Rapid leaf and stem development begins, and the plant starts forming a thick central stem with branching shoots. This growth phase is crucial for developing a robust structure that supports future flowers and fruit.
As the plant outgrows its starter container, it may need to be transplanted into a larger pot or directly into the garden. Transplanting is also a good time to introduce nutrients. “Your new seedlings will appreciate a fertilizer boost at transplanting,” says Mercer. “Don’t go overboard, though. It’s best to start with half the recommended ratio.”
4. Flowering Stage (Weeks 5–8+)
As tomato plants mature, clusters of small yellow flowers begin to appear at the tips of branches. These blooms contain both male and female reproductive parts, allowing tomatoes to self-pollinate. In outdoor gardens, wind and pollinators, such as bees, usually handle the job. Indoors, you may need to lend a hand by gently shaking the plant or using a small brush to transfer pollen from one flower to another.
“If plants are slow to flower, the problem could be your choice of fertilizer,” says Mercer. “Consider switching to a product with a lower nitrogen ratio. That’s the first number in the N-P-K ratio on the package. A bloom-boosting N-P-K of 5-10-10 will help speed up flowering.”
5. Fruiting and Ripening (Weeks 8–12+)
After successful pollination, the flowers begin to transform into small green fruits. As the season progresses, these fruits mature and ripen, changing color and texture depending on the tomato variety and temperature conditions.
This stage often brings challenges such as fruit splitting, blossom end rot and pest infestations. “Once your plants are in the ground, consistent moisture levels are key,” says Mercer. Many new gardeners believe blossom end rot is caused by a calcium deficiency. While that can be partly true, Mercer explains that most soils already contain sufficient calcium. “The problem comes with needing enough moisture in the soil to move the calcium to the fruit as it’s forming,” she notes. “Drip irrigation makes this easy, but if you don’t have it, be sure to check the soil every day and water when it feels dry, especially on hot summer days.”
FAQ
How long does it take to grow tomatoes from seed to harvest?
Most tomato plants take 60 to 100 days from seed to ripe fruit, depending on the variety.
When is the best time to start seeds indoors?
The best time to start tomato seeds indoors is typically 6 to 8 weeks before your area’s last expected frost date. This allows enough time for the seedlings to develop before being transplanted outdoors once the risk of frost has passed.
When should I transplant tomato seedlings outdoors?
Once night temperatures stay above 50°F (10°C) and plants have 2 to 3 sets of true leaves.
Why are my tomato flowers falling off without fruit?
This could be due to poor pollination, excessive heat or nutrient imbalance.
Debbie Wolfe is a writer, photographer, and author. She has contributed hundreds of home and garden articles and DIY tutorials to leading media outlets and retailers. Debbie covers all home and gardening topics and has published hundreds of DIY tutorials with step-by-step photography for leading home and garden media outlets.
