Tomato Germination and You: How It Works

Really, the tomato is a favorite food in the vegetable garden, especially when it comes to growing tomato plants from seeds. Seeds for popular varieties are available from any major seed dealer. Learning to germinate and plant tomatoes is important because tomato gardening is so rewarding!

Gardening enthusiasts meet to discuss growing tomato plants as soon as spring arrives. You can easily grow tomatoes indoors in tents, greenhouses, or hydroponic systems with the appropriate amount of light and the right temperature. When you start out with tomato seeds, you will have plenty of experience growing food. And the difference in taste between a tomato grown in the supermarket and one grown in the garden cannot be denied.

Growing tomato plants from seeds is great for anyone who wants to get a taste of the tomato plant life cycle. But what happens when the tomatoes germinate? Let's delve into the botanical aspects of gardening tomatoes from seeds.

Germination of tomato seeds

Germinating tomatoes is a fascinating process. Source: Falequin

Before a tomato seed becomes a seedling, it must go through an enzymatic process called germination. Here is a basic overview of this process.

Tomato Seed Botany

A seed begins as a dormant cell called an embryo, which is surrounded and protected by a seed coat and an endosperm. In the Solanoideae subgroup, which includes tomatoes and peppers, the seed coat is relatively thin. It is broken by exposure to the right temperature and humidity.

The endosperm supplies the seed embryo with starches that support germination. A cap covers the embryonic root, and when heat and moisture decompose the seed coat, the root and cotyledon break out of the seed. The cotyledon rises to take in nutrients from over tomato seedlings via sunlight, and the root embryo dips down to take in nutrients from the growing medium. Tomato seeds contain a cotyledon that becomes the first leaves of tomato seedlings. The cotyledon absorbs nutrients and ultraviolet light to feed young plants.

How to germinate tomato seeds

Cherry tomato seedlingTomatoes, like these coconut pellets, can sprout in peat or coconut. Source: Detsang

There is no specific way to sprout tomatoes. They can thrive outdoors, indoors, or even in a hydroponic system. Starting tomato seeds is a breeze!


Start tomatoes in bowls with potting soil. Seed starter pellets can also be used, but we strongly recommend Epic 6-Cell Seed Starting Trays. Place on a heating mat. Start by sowing from about 1 cm deep and cover the tray or starter pot with plastic wrap to trap heat and moisture. Keep the mat heated in the 60 to 70 Fahrenheit range. Seeds should germinate within one to one and a half weeks. If the seeds take a long time to germinate, it is often a sign that there is not enough heat to germinate. Just raise the temperature on your heating mat when you notice.

Place tomato plants in a sunny south window in the northern hemisphere or in a sunny north window in the southern hemisphere. Try not to expose your seedling containers to sunlight for too many hours. A range of a few hours per day for seedlings with a temperature range of 50-70 Fahrenheit is ideal. Too much heat from the sun burns plants. Note that sprouting on a warm windowsill can produce long-legged seedlings. If possible, use a grow light instead.

Build tents

Tents are a great way to control the climate around your seedlings and ensure higher germination rates. Start by starting seeds in potting soil in containers and placing them in your tent. You can also plant them in a soilless mix like coconut or a combination of vermiculite, perlite, and sand. Whichever mixture you use, make sure it is suitable for tomato seedlings. Adjust the temperature and humidity in your tent as needed. Then plant them in a larger pot when the cotyledons fall off. For example, if the floor looks a bit moldy, it could be a sign that the humidity is too high.


A tomato plant can also be grown in a hydroponic system. In this way, you will get a good, healthy yield with each plant, save water and carefully control the climate. However, if the pH in your nutrient mix drops even slightly, all of your exertion may fail. For hydroponics, plant in a soilless mix. Then seedlings in your hydroponic system should be planted in the nutrient solution with a pH of around 4.5.


If you live in a warm place with a long growing season, you can plant seeds directly in the soil of your garden outdoors if the temperature is right. This is the riskiest way to start seeds as they are fully exposed to the elements. Animals, insects, and heat can quickly damage seeds. Gardeners who start seeds outdoors need to carefully observe and be cautious about them.


Seedlings that are planted outdoors need to be cured in their pots for a few weeks. To harden your tomatoes, place the seedlings in a partially sunny area of ​​your garden for a few weeks. Check them out often. Then transplant them in a container or in the ground.

Storage and preparation of tomato seeds for germination

If you learn to collect and store tomato seeds, you can keep your favorite varieties for years. Through the process of seed fermentation, you can reduce the chance of disease and promote growth.

Seed fermentation

In the tomato flesh there is a gelatinous shell that protects the seeds. Try planting seeds directly from a tomato without removing that shell and you will find that it won't germinate as easily. To prevent seed diseases and erode the seed coat, ferment them.

Pull out any seeds you want to store with the gelatinous sheath attached. Then immerse the mass in clean water, preferably in a jar with a lid. Place the jar in a location with temperatures around 70 degrees Fahrenheit away from direct sunlight.

Stir the liquid once or twice a day to separate the seeds from the mass. This also prevents mold. After three days, move the mass to a new container that is at least three times the size of the original glass and contains three times as much water. Then remove the gel when the seeds fall to the bottom of your container. These seeds on the ground are the most viable. Rinse off any remaining non-seeds in a colander or colander. Place clean tomato seeds on a cheesecloth or paper towel to drain. You need to dry in an area with good ventilation for at least 5 days.

To prevent sticking, stir the seeds on the cloth or paper towel every day. After drying, store the tomato seeds in a cool, dry place or in the refrigerator for up to six years.


Vivipary in tomatoVivipary in a tomato. The seedlings can sometimes manage to penetrate the tomato skin in search of light. Source: Mykhal

Sometimes seeds begin the germination process within the tomato flesh. This phenomenon is known as vivipary and occurs when ripe fruits are left in conditions where tomato seeds are likely to sprout. They become a mixture of dormant and sprouted seeds. Contrary to popular belief, vivipary sprouts are edible and can be planted to start tomato seedlings as long as the tomato they are in is not moldy or damaged. However, you will have more success cultivating tomato plants from seeds that you sprouted yourself.

Testing of tomato seeds

Use a plastic bag to test tomato seeds that were saved eons ago. Place the seeds between a folded, damp paper towel and place them in a warm place out of direct sunlight. Leave the bag partially open to allow the correct air to flow. The seeds germinate within a week.

Document which seeds are sprouting, which need to be discarded due to mold / damage, and which are not responding at all. Divide the number of successful seeds by the total amount started and that is your germination rate. Transfer tomato seeds to a growing medium as soon as they sprout.

Germination conditions

Tomato seeds don't need light to germinate, but they do need the right warmth and humidity. Temperatures around 70 degrees are ideal. Temperatures between 50 and 75 will also work. Tomato seedlings prefer well-drained sandy loam soils with a pH between 6.0 and 7.0. Use a pH tester to make sure you have the correct acidity for good growth.

When using soilless media like coconut, plant as you would in a container to begin with. Do the same for hydroponics. In a hydroponic system, make sure that the right mixture of nutrient solution is applied to your plants to keep the pH balanced. Tomato seeds require adequate planting depth in order to sprout. Too deep and the cotyledons cannot reach for nutrients above the soil surface. Too shallow and roots do not form.

Tomato plants do best if you plant them at the right time, including indoors or in an air-conditioned situation. Planting in good soil in early April promotes proper growth of tomato plants.

Tomato seeds need a decent amount of moisture and moisture to grow. Keep the soil moist, but not too moist. Bottomless media require less water because they hold back more water. Use your finger to test a few inches into the medium. When it's dry it's time to water.

Germ problems

Newly emerged tomato seedlingThis seedling tomato is so young that its cotyledons have not yet spread. Source: The Ewan

Most germ problems can be traced back to incorrect temperature, soil or too much light. Let's cover some of these, and how to fix problems that may arise when starting tomato plants.

Old seeds

The germination rate of tomato seeds decreases significantly when they are too old. A seed variety that originally had a 90% germination rate could drop to 50% or less. Most stay with the same viability for up to six years. Use the test method from this article to determine age germination rate.

Improper conditions

If the temperature is too cold or too hot, tomato seeds may not grow properly. Too hot a temperature will cause the seeds to dry out and burn, ending their lives before they begin. Cold temperature conditions do not dry out the soil between waterings and cause seed rot. Germination takes much longer even at temperatures below 65 degrees. For this reason, a heating mat is an important part of tomato seed germination as it provides warm temperatures for ideal germination.

After sprouting, keep an eye on your tomato seedling to make sure they are not showing any signs of becoming leggy from a lack of light. They don't need light to germinate, but they do need it when they are above the ground!

frequently asked Questions

Newly sprouted tomato seedlingsAll tomato seedlings look similar if they still show cotyledons. Source: Superrad

Q: What's the fastest way to sprout tomato seeds?

A: The fastest way to sprout a tomato seed is with the test mentioned in this article. Place tomato seeds between a folded, damp paper towel and place them in a plastic bag. Hold the bag slightly open to allow air to circulate. You will have tomato sprouts in about a week.

Q: Do tomato seeds germinate better in the dark?

A: Tomato seeds don't need light to germinate. And too much light can make your resulting seedlings spindle-shaped. Try germinating seeds in starting trays with a warming mat or in a plastic bag with a paper towel. The plastic ensures that there is enough moisture for the seeds to grow.

Q: Do I water tomato seeds before planting?

A: You can, but it's not necessary for germination. Moist growing medium is enough!

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