If you are planting (or have already planted) tomato seeds, you are probably wondering just how long they take to sprout. You may also be curious about how you can speed up the seed germination process.
So, how long do tomato seeds take to germinate? Tomato seeds take 6 to 11 days to germinate, and the ideal soil temperature is 65 to 85 degrees Fahrenheit (18 to 29 degrees Celsius). Tomato seeds germinate faster with optimal soil temperature, humidity, and air circulation.
Of course, you can germinate tomato seeds directly in the soil outdoors, or you can germinate them indoors to transplant outside several weeks later.
In this article, we’ll take a closer look at some of the factors that affect how long tomato seeds take to germinate. We’ll also see how we can optimize these factors to encourage faster germination to get your seeds sprouted sooner.
Let’s get started.
How Long Do Tomato Seeds Take To Germinate?
Normally, tomato seeds will take 6 to 11 days to germinate (about 1 to 1.5 weeks). The University of Maryland suggests that tomato seeds can germinate in as little as 5 days, while the University of Maine suggests that tomato seeds can take up to 11 days to germinate.
It will all depend on various factors that affect time to seed germination – let’s get into some of those now!
What Factors Affect Tomato Seed Germination?
The time a seed takes to germinate depends on several important factors, such as soil temperature, humidity levels, and air circulation. Let’s dive into more detail on these factors that affect seed germination.
Soil Temperature
The temperature of the soil (growing medium) will affect the time it takes for seeds to germinate. Soil temperature will also have an effect on germination rate, or the percentage of seeds that sprout.
***Note: You can find the germination rate on the seed packet itself. For example, if the germination rate is 95%, then you would expect 95 seeds to sprout out of every 100 seeds that you planted.***
The minimum temperature for tomato seed germination is 50 degrees Fahrenheit (10 degrees Celsius). If the soil is any colder than this, you will see low germination rates – that is, if you can get any seeds at all to germinate! This is nature’s way of protecting tomato seeds from sprouting at a time when they will be unable to survive.
The maximum temperature for tomato seed germination is 95 degrees Fahrenheit (35 degrees Celsius). If the soil is any warmer than this, germination rates will decrease. Combined with high humidity, high temperatures can encourage the growth of mold, which is another threat to your plants.
The ideal (optimal) temperature for tomato seed germination is between 65 degrees Fahrenheit (18.3 degrees Celsius) and 85 degrees Fahrenheit (29.4 degrees Celsius).
Keep in mind that these temperatures refer to soil temperature, not air temperature. If you want to find out the soil temperature, use a probe-type thermometer to check.
If the thermometer reads a temperature that is too low, then you have some options. One option is to put a heating mat below the seed tray to increase the temperature of the soil.
You can also put lights (or heating lamps) directly overhead. This is a good option, since tomato seedlings will need light to continue their growth after germination.
For more information, check out the table below, and check out this article from the University of California on ideal seed germination temperatures.
| Seed Temp | Temp (degrees F) | Temp (degrees C) |
|---|---|---|
| Min | 50 | 10 |
| Ideal | 65 to 85 | 18 to 29 |
| Max | 95 | 35 |
maximum temperatures for
tomato seed germination.
Humidity
Humidity is another important factor to consider when germinating tomato seeds. If the air is too dry, then the soil will dry out faster, and the seeds will have trouble germinating – they may even die!
If the air is too humid, then the soil will stay too wet, especially if you over water the seed tray. This can lead to damping off, which occurs when mold or other pathogens affect seeds or seedlings.
Damping off is more likely with high humidity levels, in moist soil, and at cooler temperatures.
For more information, check out this article on damping off from Wikipedia.
If you find that you have trouble keeping the air and soil humid enough, you do have some options. One option is to use a humidity dome.
A humidity dome traps moisture in the air and soil so that seeds have the humid environment they need to germinate properly. A humidity dome will help your seeds to germinate faster, increase germination rates, and cut down on the time and effort needed to keep soil moist.
For more information, check out my article on humidity domes.
As an alternative, you can use clear plastic (such as plastic food wrap) to cover the seed tray. This will trap moisture in the air under the plastic and keep the soil moist for a longer time after watering. Just make sure to prevent the plastic from coming in contact with the soil.
Air Circulation
Seeds need air, just like seedlings and established plants. If the soil is too wet and there is too little air circulation, it can spell death for your seeds before they even have a chance to sprout.
To keep your seeds from suffocating due to lack of air, there are two key things you can do.
First, keep the soil moist, but not wet. Do not over water the soil, and consider using a humidity dome to help you to get the right moisture level.
Second, keep the soil loose. Do not compact the soil by pushing down on it either before or after planting your seeds. When there is more space between soil particles, there is more space for air and water, both of which are necessary for seed germination.
How Do I Make Tomato Seeds Germinate Faster?
If you want to make your tomato seeds germinate faster, there are several important actions you can take.
First, protect your seeds from extreme heat and cold. As mentioned earlier, temperature is one of the most important factors that affect seed germination.
If it is too cold to plant seeds outside, then start your seeds indoors. This gives you a head start on the growing season, and minimizes the danger of late spring frosts killing your seedlings. This is especially helpful if you live in an area with a short growing season.
Second, ensure that the soil is moist (not wet!) and the air is humid. Seeds will not germinate if there is not enough moisture in the soil and air. Consider a humidity dome for this purpose.
Third, make sure that the soil has enough air circulation. This means that you should avoid compacted soil both before and after planting. It also means that you should avoid over watering your soil.
Fourth, remember that tomato seeds germinate better in the dark. After germination, give the tomato seedlings bright overhead lights. Otherwise, they will get leggy (leggy means tall and stretched out, which occurs when a plant reaches for scarce light in dark conditions).
Fifth, make sure to plant your tomato seeds according to the proper depth and spacing. Tomato seeds should be planted at a depth of 0.25 inches (0.64 centimeters). The seeds should be 4 inches apart, to allow each seedling its own space in the soil to grow roots.
Finally, you can scarify (scratch the surface) of your seeds in order to encourage germination. This can speed up germination and also increase germination rate (the percentage of seeds that sprout).
For more information, check out this article on seeds and seedlings from the Penn State University Extension.
Should Tomato Seeds Be Soaked Before Planting?
According to the cooperative extension, there is no need to soak tomato seeds before planting them. As long as the growing environment is moist and warm, they should germinate well.
Can You Germinate Tomato Seeds In A Paper Towel?
Yes, you can germinate tomato seeds in a paper towel. The paper towel holds moisture and allows the seeds to breathe, serving as an alternative growing medium.
To germinate tomato seeds on a paper towel, wet the paper towel until it is damp (not soaking wet). Then, lay out the tomato seeds so that they are separated (not touching).
Be sure to keep the paper towel and seeds in a warm place, to encourage faster germination and higher germination rates.
The only drawback of this method is that you will need to transplant the sprouted seeds into soil by hand, since they will soon need nutrients from the soil to grow and establish stronger roots. Be gentle when handling the tiny sprouted seedlings!
Why Are My Tomato Seeds Not Germinating?
There are a couple of possible reasons that your tomato seeds are not germinating.
Your Tomato Seeds Are Too Old
One common reason for a lack of germination is that the seeds you are using are too old. In that case, the germination rate may be low, or even zero.
Tomato seeds tend to last about 3 years, and germination rates will naturally decrease with each passing year. For more information, check out my article on how long seeds last.
Your Soil Is Too Cold Or Too Dry
Another reason your tomato seeds are not germinating has to do with soil conditions.
If the soil is too cold, then your tomato seeds might not sprout right away (whether you are growing indoors or outdoors). They may sprout when conditions improve and the soil warms up.
However, you might not want to wait that long, and you might not want to risk killing your seeds. In that case, start the seeds indoors, and use a heat lamp or heat mat to keep the soil warm enough so that the seeds can germinate.
Finally, remember that if the soil is too dry, then seeds will not germinate, and they may even die before you have a chance to correct the problem. Keep the soil moist, and consider using a humidity dome to help maintain the proper moisture levels in the soil and air.
If you have trouble with dry soil, check out my article on how to treat dry soil.
Will Fresh Tomato Seeds Germinate?
Fresh tomato seeds will germinate just fine. The seeds do not need to be aged or dried in order to sprout and begin growing.
However, some gardeners suggest fermenting tomato seeds before trying to store or germinate them. According to Garden Myths, fermentation of tomato seeds is not necessary, but it may help to destroy some common diseases, such as bacterial canker.
Of course, if you want to save the seeds for long-term storage, you should dry them out first. You can learn more about how to save seeds in my article here.
How Big Should Tomato Seedlings Be Before Transplanting Outdoors?
Usually, you should aim to transplant tomato seedlings outdoors after the last frost date, since tomato plants will not survive a frost.
To find out the last frost date in your location, check out this frost date calculator from the Old Farmer’s Almanac.
A good time to transplant tomato seedlings outdoors is after the first “true leaves” appear on the plant. These are not the leaves that grew out of the seed when it sprouted, but rather new leaves that grew after the initial germination period.
You can learn more about when and how to transplant tomato seedlings outdoors in my article here.
Conclusion
By now, you have a good idea of how long it takes tomato seeds to germinate. You also know about the factors that affect time to germination, how to optimize for faster germination, and how to troubleshoot a lack of germination.
I hope you found this article helpful in sprouting your tomato seeds – if so, please share it with someone who can use the information.
If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy!
~Jonathon
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