How To Save Tomato Seeds For Next Year
Have you ever wondered how to save tomato seeds? We provide an in-depth explanation of different methods to use to keep your seed supply up!
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Have you ever wondered how to save tomato seeds? Many gardeners put so much time into growing their plants that it feels like a waste to enjoy the harvest for only one growing season. Whether you are planning to save heirloom tomato seeds or simply want to learn the basics, this guide covers all aspects of tomato seed saving.
Seed saving starts with the harvest, and the first step is learning how to harvest tomato seeds correctly. This guide also explains how to save tomato seeds without fermenting, how to ferment tomato seeds when needed, how to dry them properly, and how to store them for long-term use.
If you want to start saving tomato seeds every year, this guide walks you through everything you need to know to do it successfully.
Choose Your Tomatoes Wisely
What kind of tomatoes are you growing, and are they open-pollinated varieties?
When you grow tomatoes, the seeds that develop are influenced by what pollinated the parent plant’s flowers. For example, if you are only growing the ‘San Marzano’ variety of paste tomatoes, even if bees cross-pollinate the plants, they will usually breed true as ‘San Marzano’. This is an example of single-variety open pollination.
However, open-pollinated varieties can be cross-pollinated by other tomato types. Imagine you are growing ‘San Marzano’ alongside ‘Cherokee Purple’, ‘4th of July’, and ‘Yellow Pear’. That gives you one paste tomato, one heirloom slicer, one salad slicer, and one cherry tomato variety growing in the same space. Bees can move pollen between all of them.
The fruit produced by those plants will still taste like the tomatoes you planted, but the seeds inside may now carry traits from other varieties. This is how hybridization begins over multiple generations.
For the most consistent tomato seed saving results, it is best to grow just one tomato variety in a given area. Doing this reinforces that cultivar’s genetics, and over time the plants may even adapt better to your local climate. If you do not mind gradual changes, cross-pollinated seeds will still grow, but you may want to purchase fresh seed every few years to return to a more stable form.
When saving tomato seeds, select only the best fruit. Choose tomatoes that are large, juicy, and visually impressive, and mark them ahead of time. A simple piece of yarn tied around the branch near the fruit works well. Allow these tomatoes to fully ripen on the vine, then leave them until they are slightly overripe and soft.
By pre-selecting and waiting for these prime tomatoes, you ensure that your saved seeds come from the best possible fruit. This greatly increases your chances of growing more tomatoes with those same desirable traits in future seasons.
Fermenting Tomato Seeds
Tomatoes have natural germination inhibitors surrounding their seeds. The gelatinous coating around each seed prevents sprouting. On one hand, this stops tomatoes from germinating new plants while still on the vine. On the other, it means that to get the best quality seeds, that gel needs to be removed.
The easiest way to remove it is through tomato seed fermentation. As the gelatinous coating breaks down, the seeds are released and become free to germinate. Each tomato variety should be fermented separately and never mixed with seeds from other varieties.
Start by washing the tomatoes thoroughly to remove any dirt from the skin. This helps reduce the risk of soilborne bacteria contaminating your seeds. If the tomatoes are very soft, handle them carefully so they do not burst open during washing.
Harvest Seeds
Now it is time to look at how to harvest tomato seeds. Slice the tomatoes cleanly in half or into quarters lengthwise. Holding the stem end of the tomato, gently squeeze the seeds and surrounding pulp into a bowl. It helps to sacrifice a few overripe tomatoes and squeeze them completely into juice, as this liquid speeds up the fermentation process. Any leftover tomato flesh that is seedless and still in good condition can be dehydrated and used like sun-dried tomatoes.
Transfer the tomato juice, seeds, and gel into a quart-sized mason jar. Ideally, there should be enough juice so that once fermentation is complete, the seeds are separated from the remaining gel by liquid. If there is not enough juice, do not add water. Diluting the mixture will slow down the fermentation process and reduce its effectiveness.
Maintenance
Once the lid is on the jar, give it a good shake and set it in a location that stays at 70°F (21°C) or cooler. Once or twice a day, shake the jar to help dislodge the seeds from the gel. Be sure to open the jar at least once daily to burp it and release gases produced during fermentation. The smell can be unpleasant, but that is normal. Continue this process for at least three days and up to a week.
At the end of fermentation, add about three times as much water to the jar, shake it again, and let it sit for about one hour. Most viable seeds will sink to the bottom, while the gelatinous layer and non-viable material float on the surface. Use a spoon to skim off the gel layer and discard it.
Pour off some of the cloudy liquid, add fresh water, shake, and repeat the draining process until the water appears mostly clear. Each time, allow the contents to settle so viable seeds sink and non-viable material floats, then remove the debris. Once the water is clear, pour the seeds into a fine mesh strainer and rinse them thoroughly.
If you are processing a large quantity of seeds, you can speed things up by removing the initial gel layer, then dumping the remaining contents onto a large screen or into a wide mesh strainer. Spray with a strong stream of water. The seeds will remain in place while any remaining pulp washes away.
Treat Seeds
SAt this stage, some people choose to treat their seeds to prevent the transmission of disease. This step is optional, but it is recommended if you plan to share seeds with others.
To treat the seeds, prepare a 10 percent bleach solution using one part bleach to nine parts water. Soak the seeds for 30 minutes. Immediately pour the seeds back into a strainer and rinse them under cold running water for at least seven minutes. Stir or agitate the seeds constantly during rinsing to ensure all traces of the solution are removed. Once the seeds have been rinsed for at least seven minutes, you can move on to drying.
The reason for rinsing for seven to eight minutes with constant agitation is to reduce residual chlorine levels from the bleach solution. This brings chlorine content below the National Organic Program threshold. For seeds to be considered organic, residual chlorine levels must be under four parts per million.
How To Dry Tomato Seeds
Cool, well-ventilated conditions are essential for drying tomato seeds. If the environment is too hot, such as when using dehydrators or similar machines, the seeds can effectively be cooked and rendered sterile. That is the last thing you want.
You can air-dry tomato seeds in a dry location. One effective method is to make a simple wooden drying frame using scrap wood and an old window screen. Attach the screen to the frame with a staple gun, then spread the seeds evenly across the surface. Place the frame in a well-ventilated, dry area and allow the seeds to dry naturally.
If you prefer not to build a drying frame, line a baking sheet with parchment paper and spread the seeds out in a single layer. This method takes a bit longer, but the seeds will still dry successfully over time. Some people use paper plates, but seeds often stick to them and can be difficult to remove. Parchment paper works better because it is flexible, allowing you to bend it slightly and release stuck seeds easily.
Every one to two days, gently stir the seeds to ensure even drying. Break apart any clumps with your fingers or rub them lightly between your hands so they separate fully.
Another option for drying seeds without heat uses a box fan, two inexpensive air filters, and a few bungee cords. After fermentation, sandwich the tomato seeds between the air filters and secure them to the front of the fan. The fan pushes cool air through the seeds, drying them much faster than leaving them in still air.
Saving Tomato Seeds Without Fermenting
It is possible to save tomato seeds without fermenting them. Over time, the gelatinous coating around the seeds will naturally break down, which is why planting a piece of seedy tomato can result in sprouts. This approach works well if you are only saving a small number of seeds for personal use and do not plan to treat them to prevent disease transmission.
For this method, you will need paper towels, a pair of tweezers, and a fresh tomato. Cut the tomato open and scrape the seeds into a bowl. Using the tweezers, pick up individual seeds along with their gel coating and press them onto a paper towel, spacing them out so they do not touch. Place the paper towels in a dark, cool, well ventilated area and allow the seeds to dry completely.
Once dry, the seeds will adhere to the paper towel. You can fold the towel and store it for later use, and even label it with the tomato variety if desired. When planting time comes around, simply cut or tear off small sections of the towel containing seeds and plant them directly in the soil. The paper towel will break down naturally, allowing the seeds to germinate.
Keep in mind that this method does not reduce the risk of disease transmission. Because the dried gel remains on the unrinsed seeds, there is a small chance of spreading disease if the parent plant was infected. That said, the risk is generally low if your plants were healthy.
Long-Term Storage
Three words apply to storing tomato seeds: cold, dry, and dark.
You do not need to freeze your seeds, as tomatoes do not require extreme cold. However, they do prefer cooler temperatures. When possible, aim for a storage range of 40 to 60°F (4 to 16°C). If your home typically stays around 70°F (21°C), that is still perfectly acceptable.
Keeping seeds dry is essential. Moisture is what triggers germination, and tomato seeds will readily sprout in the dark if moisture is present. Storing seeds in an airtight container helps prevent this. Paper envelopes placed inside the container work well, especially when paired with a moisture-absorbing silica packet.
Darkness is the final key factor. While seeds do not need light to germinate, darkness helps prevent premature sprouting when combined with cool, dry conditions. Without warmth or moisture, a dark environment is ideal for long-term tomato seed storage.
