Germination – Page 3 – GreenUpside – Learn how to grow a green garden with us!

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 to reduce tomato seed germination time and speed up the process of sprouting. So, how long do tomato seeds take to germinate? Tomato seeds germinate in 6 to 11 days in ideal conditions. The best soil temperature for tomato seed germination is 65 to 85 degrees Fahrenheit (18 to 29 degrees Celsius). Tomato seeds also germinate faster with proper soil moisture. The germination rate of tomato seeds depends on their age. You can see how soil temperature affects seed germination with this app I made! Of course, you have two choices when it comes to tomato seed germination: you can sow seeds directly in the soil outdoors (best for warm regions), or you can start them indoors to transplant outside several weeks later (best for cold regions). 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 show you how to optimize these factors and encourage faster tomato seed germination time. Let's get started. (If you want a complete seed starting walkthrough with video and other resources, check out our seed starting course today!) How Long Do Tomato Seeds Take To Germinate? Normally, tomato seeds 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. Tomato seeds will usually take 6 to 11 days (1 to 1.5 weeks) to germinate under ideal conditions. Tomato seed germination time depends on several factors – let’s get into some of those now! What Factors Affect Tomato Seed Germination? Tomato seed germination time depends on several important factors, including: Soil temperature Soil moisture/humidity levels Air circulation Let’s dive into more detail on each of these factors that affect tomato seed germination. We'll start with soil temperature Soil Temperature The temperature of the soil (growing medium) will affect the time it takes for seeds to germinate. In fact, it is one of the biggest factors that determines how long before tomato seeds sprout. Soil temperature also has an effect on germination rate, or the percentage of seeds that sprout. (You can learn about germination rates and how to do a seed viability test here). ***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 other 5 seeds would never sprout!*** The minimum temperature for tomato seed germination is 50 degrees Fahrenheit (10 degrees Celsius). At this temperature, it can take up to 6 weeks for seeds to sprout! Below this temperature, don't expect much to happen at all. If the soil is any colder than 50 F, 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. Since tomato plants are vulnerable to cold (and are killed by frost), you don't want them to emerge from the soil before the danger of frost has passed. (You can learn how to protect tomato plants from cold and frost here). This is why it is often suggested that you transplant tomato starts outside a couple of weeks after the last spring frost date. (You can find the last spring frost date in your area with this tool from the Old Farmer's Almanac). The minimum temperature for tomato seed germination is 50 degrees Fahrenheit (10 degrees Celsius). They take quite some time (up to 6 weeks!) to sprout in such cool soil. 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 encourage the growth of mold, which is another threat to your tomato seeds (and seedlings). The ideal (optimal) temperature for tomato seed germination is between 65 and 85 degrees Fahrenheit (18.3 to 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. (There are other ways to keep seeds warm too - you can learn more here.) For more information on soil temperatures for tomato seed germination, check out the table below, and check out this article from the University of California on ideal seed germination temperatures. SoilTempTemp(degreesF)Temp(degreesC)Min5010Ideal65 to 8518 to 29Max9535This table shows minimum, ideal, &maximum temperatures fortomato seed germination. Soil Moisture/Humidity Soil moisture and 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 often leads 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. It can also occur if you reuse seed trays that were not washed out and sterilized (with alcohol or bleach) after last year. (For more information, check out this article on damping off from Wikipedia). If you find that you have trouble maintaining soil moisture and humidity, 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 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. You can use plastic wrap to cover your seed tray to maintain high humidity levels for longer periods of time. 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. If necessary, vent it by removing the plastic to avoid soggy soil. Wet soil is one way to deny seeds the air they need to survive and thrive. Speaking of which - let's get to air circulation next. 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 will spell death for your seeds - sometimes 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. If you want your seeds to sprout into seedlings, make sure that they have enough air during the germination period. Do not compact the soil by pressing it down hard! First: keep the soil moist, but not soggy. 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 proper seed germination. How Do I Make Tomato Seeds Germinate Faster? If you want to make your tomato seeds germinate faster, there are several ways to do it. 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. If it is too cold for seed germination outside, then start your tomato seeds indoors, and transplant them outdoors later. Second, ensure that the soil is moist (not soggy!) 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 (soil and air above it) is warm with enough moisture, 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. You can use damp paper towels for your seed germination medium, as an alternative to soil. Just remember to be gentle when transplanting the tiny seedlings into soil after they germinate! 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 on the paper towel 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 to avoid damaging them! Why Are My Tomato Seeds Not Germinating? There are a couple of possible reasons that your tomato seeds are not germinating. One possibility is that your seeds are too old. Your Tomato Seeds Are Too Old One common reason for a lack of germination is that the seeds you planted are too old. In that case, the germination rate may be low - or even zero. If you save tomato seeds and forget about them for too long, they may not germinate due to old age. 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. They may even die before you have a chance to correct the problem. Keep the soil moist (a spray bottle or plant mister helps with this!) Also, consider using a humidity dome to help maintain the proper moisture levels in the soil and air. Dry soil will prevent tomato seeds from germinating - be sure to keep the soil moist and the air humid. (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. To avoid the spread of pathogens, use certified disease-free seeds when growing tomatoes (or other crops). 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? Michigan State University suggests starting tomato seeds indoors 5 to 7 weeks before it is time to transplant them outdoors. Usually, you should aim to transplant tomato seedlings outdoors after the last frost date. Tomato plants are tender, and they 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 "true leaves" are not the leaves that grew out of the seed when it sprouted. Rather, they are the new leaves that grew after the initial germination period. Wait until after the first "true leaves" appear on a tomato seedling before you transplant it outside (in general, the plant should be at least 6 inches tall). The University of Arizona suggests transplanting tomato seedlings outside when the plants are 6 inches (15.2 centimeters) tall. You can learn more about when and how to transplant tomato seedlings outdoors in my article here. Conclusion Now you have a good idea of how long it takes tomato seeds to germinate. You also know about the factors that affect tomato seed germination time, how to optimize for faster germination, and how to troubleshoot a lack of germination. You can learn more about what it means for tomato plants to be self-pollinating in my article here. You might like to read my article on how long it takes tomato plants to bear fruit (from seed to mature fruit). You might also be interested in reading about when you can direct sow tomato seeds - and when you might be better off starting seeds indoors. You can learn more about everything you need to grow tomatoes in my article here. You can learn more about the tomato tree (a relative of the tomato) here. I hope you found this article helpful in sprouting your tomato seeds – if so, please share it with someone who can use the information.