A Quick Guide to Germinating Tomato Seeds

Can you grow a new tomato plant from the seeds you got from the tomatoes? The quick answer is yes! 

But germinating these tomato seeds is the crucial and often neglected part of this planting journey. Honestly, this process will either make or break the future of your tomato plant. 

To make sure that you’ll have a successiful seed germination experience, we’ll guide you every step of the way and help you understand the different factors affecting seed germination. 

How long do tomato seeds take to germinate?

Tomato seeds germinate within 6 to 11 days (1 to 1 ½ weeks) from planting. They sprout fast under moist soil and warm conditions. 

The seed will break open and become a seedling with newly-formed roots, stems and leaves.

What are the factors affecting tomato seed germination?

The success of tomato seed germination depends on air circulation, soil moisture, and soil temperature. 

Let’s understand how each of these factors affects tomato seed germination. 

1. Air Circulation

Make sure that there’s proper air circulation during the seed germination period. If the soil is too wet with little air, it can kill your seeds before they even get the chance to sprout. 

You can keep the soil moist but not soggy or keep the soil loose to ensure proper air circulation. Do not push down or compact the soil so that there is more space for air and water, vital in germination.

2. Soil Moisture

Soil moisture and humidity should also be considered in germinating tomato seeds. If the soil is dry, it will be difficult for the seeds to germinate and can even cause death. 

High humidity, conversely, translates to wet soil that can cause mold or attract pathogens that can infect tomato seeds and seedlings. 

You can use a humidity dome or plastic wrap to cover the seed tray and trap moisture in the air and soil. This will speed up germination and increase its success rate. 

3. Soil Temperature

Soil Temperature	Temperature in Fahrenheit	Temperature in Celsius
Minimum	50	10
Optimal	65 to 85	18 to 29
Maximum	95	35

As the growing medium, soil temperature affects the time it takes for the tomato seeds to germinate and its success rate.

The optimal soil temperature for tomato seed germination is between 65 and 85°F (18.3 to 29.4°C). You can use a probe type to check the soil temperature and adjust accordingly. 

If the temperature is too low, you can put a heating mat below the seed tray or place heating lamps above it. 

The minimum temperature for tomato seed germination is 50°F (10°C). Under this condition, your tomato seed will sprout within six weeks.

Unfortunately, a temperature lower than 50°F (10°C) will result in low to no germination. This is the seed’s natural way of protecting itself from sprouting in a place where it cannot survive, such as extremely cold conditions or frost.

On the other hand, the maximum temperature for germination is 95°F (35°C).  If the soil gets warmer, the germination rate decreases and risks mold growth on the seeds and seedlings. 

How to Germinate Tomato Seeds

Difficulty	Easy ●○○○○
Duration	1 to 2 hours for preparation6 to 11 days for germination
Things You Need	• Tomato seeds • Water • Spray bottle • Fertile soil mix • Heat lamp • LED lights • Seed tray • Water soluble fertilizer • Pot

Begin germinating your tomato seeds about 6 to 8 weeks before you plant them in your garden and the last frost date. This way, there’s enough time for the tomato plant to establish itself before the frost. 

Below are steps on how to germinate tomato seeds.

How To Do 1. Use a fertile soil potting mix. Avoid using garden soil as it may have pathogens that can infect and hamper seed germination. Moisten the soil before placing them in the seed tray. Do not compact the soil to keep the seeds well-aerated. 2. Provide warmth and light to the tomato seed and seedling.  Use a heat lamp that can provide warmth at 70°F (21°C) to make the tomato seeds germinate faster.  Then, place the seed containers with access to sunlight or set up bright LED lights 24 inches (60 cm) above the soil surface once seedlings sprout. 3. Plant 2 to 3 seeds in every container. The seed trays must have at least 3 to 4 inches in height. Plant the seeds ¼ inch deep in the soil. Cover the seeds with adequate topsoil and mist the soil again with water. 4. Water tomato seeds every 2 to 3 days. Use a spray bottle to keep the soil moist. 5. Apply water-soluble fertilizer. Once you see the first true leaves of the tomato seedling, it’s safe to apply fertilizer. Use a water-soluble fertilizer to make sure the roots absorb all the nutrients directly. 6. Transplant the seedlings when they grow 6 inches tall. The best time to do so is during the early spring season. 7. Repot the tomato plant.  Once the tomato seedlings develop thicker leaves and overgrow their container, you can re-pot them into a larger one to support their full growth.

How to Germinate Tomato Seeds Faster

Here are the best practices for speeding up tomato seed germination. 

1. Protect seeds from extreme temperatures.

If the soil temperature is too cold, transfer your seed tray indoors to minimize the chances of frosts killing the seedlings. 

2. Keep the soil moist and the air humid. 

Use a humidity dome or cover the seedling tray with plastic wrap. This will keep the soil and air moist, which is crucial for tomato seed germination. 

3. Maintain air circulation.

To maintain air circulation in the soil, it’s best to keep them moist and loose. Do not compact the soil so that there’s ample space for water and air, which will aid in germinating the tomato seeds.

4. Germinate seeds in the dark. 

Another tip is to germinate tomato seeds in the dark. This prevents leggy growth on the seedlings when the plant reaches for low light in dark conditions. 

5. Plant tomato seeds in proper depth and spacing.

Tomato seeds should be planted 0.25 inches (0.64 cm) deep in the soil and 4 inches apart from others to give them enough space to develop their roots horizontally and vertically. 

6. Scarify the tomato seeds.

Scarifying means scratching the surface of the seeds to encourage their germination and increase the percentage of seeds that will sprout.

Why do tomato seeds fail to germinate?

Tomato seeds usually fail to germinate because of old seeds, cold or dry soil, lack of oxygen, overfertilization and inadequate planting depth.

1. Old Tomato Seeds

Tomato seeds have a lifespan of 3 years, and beyond that, the germination rate will decrease with every passing year. So, if you plant old tomato seeds, expect a low to zero germination rate. 

Additionally, even if these old seeds manage to sprout, the tomato plant will most likely be weak and will wilt quickly. 

2. Cold or Dry Soil

Tomato seeds fail to sprout when the soil is too cold since they protect themselves from growing in conditions where they will not survive. To help them germinate, use a heat lamp or heat mat to warm up the soil. 

Similarly, if the soil is too dry, tomato seeds will not germinate and eventually die. So, keep the soil moist using a spray bottle and a humidity dome to maintain its moist condition.

3. Lack of Oxygen

Overwatering tomato seeds prevents them from getting enough oxygen. The excess water suffocates them to death. 

To avoid waterlogging the soil, just use a spray bottle and only water the seeds when the soil is dry to the touch. 

On the other hand, you should also avoid underwatering because this prevents the seeds from breaking out of their coats and sprouting. 

Compacting the soil also deprives the seeds of the oxygen it needs to germinate. Do not push down the soil and provide ample space for oxygen particles to move freely and aid in germinating the tomato seeds.

4. Overfertilized Soil

Excessive soil fertilization causes tomato seed burn. 

This usually happens when you use uncomposted manure to fertilize the soil. Manure has high nitrogen content that definitely burns these fragile tomato seeds. 

To be safe, let the seeds germinate first and wait for the first leaves to sprout before applying fertilizer to the seedling. 

5. Planted at the Wrong Depth

Tomato seeds should be sown at 0.25 inches (0.64 cm) deep in the soil. Sow them too deep, and it will be difficult for them to sprout their way up while sowing them near the surface will cause them to be washed away easily. 

Do fresh tomato seeds germinate?

Fresh tomato seeds will germinate naturally. They do not need to be aged or dried before they can sprout. 

But there’s also no harm in fermenting or drying tomato seeds before planting them. Gardeners usually do this to destroy pathogens and prevent the spread of tomato plant diseases like bacterial canker. 

How to Store Tomato Seeds for Future Germination

Difficulty	Easy ●○○○○
Duration	• 1 hour for preparation • Two days for fermentation • Three weeks for drying
Things You Need	• Glass container • Water • Strainer • Paper towel • Plate • Air-tight container

You can also store tomato seeds for future germination. Just seal them in an air-tight container and place them in a cool, dry place. 

Below are steps on how to ferment your tomato seeds for future germination. 

How To Do 1. Remove the seeds from the tomato pulp and place them in a glass container.  2. Fill the glass container with water.  3. Leave them for two days to provide enough time for the seed coat to break and remove harmful bacteria.  4. After two days, swirl the jar until the seeds settle at the bottom and the pulp floats at the top of the mixture.  5. Use a strainer to separate the seeds from other materials. 6. Spread the tomato seeds on a paper towel to absorb excess water.  7. Place the seeds on a plate and dry them in a warm and dry area for three weeks. 8. After three weeks, keep the dried seeds in an air-tight container.

Can you germinate tomato seeds in a paper towel?

You can germinate tomato seeds in a paper towel as a useful alternative to soil. Paper towels can successfully hold moisture and provide air circulation for seed germination. 

Once you have sprouted seeds, you’ll have to transplant them into the soil by hand so they can develop stronger roots. 

Here’s how to germinate tomato seeds using a paper towel.

Difficulty	Easy ●○○○○
Duration	30 minutes to 1 hour for preparation6 to 12 days for germination
Things You Need	• Paper towel • Water • Tomato seeds

How To Do 1. Wet the paper towel until it is damp. 2. Place the tomato seeds on a damp paper towel. Make sure the seeds are not touching. 3. Fold the paper towel so the seeds will not fall from its sides. 4. Keep the paper towel with seeds in a warm place to speed up germination. 5. Wait for 6 to 12 days for the tomato seeds to germinate.

How big should tomato seedlings be for transplanting?

Tomato seedlings are best transplanted when they reach 6 inches (15.2 cm) tall. This usually happens within 5 to 7 weeks of germinating them indoors. 

The best indicator of their readiness for transplantation is the emergence of “true leaves.” They are the new leaves that grew from the seed after the initial germination period. 

FAQs on Tomato Seed Germination