Have you ever wondered how to save tomato seeds? We have all invested so much time growing our beloved plants that it is a shame to only enjoy this crop for one growing season. Whether or not you want to save heirloom tomato seeds, this guide should help you with all aspects of tomato seed storage.
But saving seeds has to start somewhere. And the first step is harvesting tomato seeds. We'll also cover methods of storing tomato seeds without fermentation, as well as how to ferment tomato seeds, how to dry them properly, and more.
So, if you're looking to start saving tomato seeds every year, this guide should walk you through everything you ever need to know!
We also have a great video showing Kevin going through the fermentation process with Brijette Romsedt from the San Diego Seed Company. You can see that here too!
Choose your tomatoes wisely
What kind of tomatoes do you grow and are they openly pollinated varieties?
When you grow tomatoes, the resulting seed of tomato varieties is developed based on the pollination of the flowers of the mother plant. Let's say you only grow the San Marzano paste tomato variety. Even if bees pollinate your plants, they will likely breed as San Marzano tomatoes. This is open pollination with one variety.
However, openly pollinated varieties can be cross-pollinated by different species. Let's say you have this San Marzano, but you also grow a Cherokee Purple, a July 4th, and a Yellow Pear tomato. This is now a tomato paste, an heirloom cutter, a salad cutter and a variety of cherry tomatoes. These can also be cross-fertilized by your bees.
The fruits resulting from these cross-pollinations may not be 100% identical to the mother plant. The fruit itself tastes like what you planted, but the seeds can now carry characteristics of other species. In this way, hybridization takes place over several generations of a plant.
For real tomato development, you should only use one variety of tomatoes in a given place. You will then strengthen the genetics of this strain and, over time, better adapt to your specific climate. If you don't mind possible gradual changes over time, cross-pollinated seeds can grow too. However, you may want to buy new seeds every few years to return to a truer form.
Pick only the best, biggest, juiciest and most impressive tomatoes to harvest your seeds from and mark them in advance. I use a piece of twine tied around the branch next to the tomato as a marker. You want them to mature on the vine, and in fact, you want to leave these on the vine until they get overripe and a little mushy.
By pre-selecting and waiting for these main candidates, you will receive seeds from this particular perfect fruit. That increases your chances of getting more fruit like this one!
Choose ripe or overripe tomatoes to save seeds.
Fermenting tomato seeds
Did you know that tomatoes have germ inhibitors around their seeds? This gelatinous coating that surrounds the tomato seeds prevents them from sprouting. On the one hand, this means that your tomatoes will not sprout any new fruit on the vine. But it also means that for the best seeds you will need to remove this gel.
The easiest way to do this is by fermenting tomato seeds. When the gel breaks down, the seeds inside are released and then free to germinate. Each variety of tomatoes should be fermented individually and not mixed with seeds of other varieties.
Start by washing your tomatoes thoroughly to remove any dirt on the outside of the fruit. It reduces the chances of soil-bound bacteria infecting your seeds. If they have become very soft, be careful not to open them in the process.
Now is the time to discuss how to harvest tomato seeds. Neatly cut the tomatoes in half or quarter along the fruit. Then, hold the stem end of the tomato and use your hand to press the seeds and pulp down into the bowl. Sacrifice a few of these overripe tomatoes to be squeezed into juice as well. This juice speeds up the fermentation process. Any leftover seedless tomato flesh that has not spoiled can be dehydrated and used like a sun-dried tomato.
Place your tomato juice, seeds, and gel in a quarter-size mason jar. Ideally, there should be enough juice in it so that the gel is separated from the seeds by some liquid when the fermentation is complete. If it doesn't, do not add water as diluting the juice will slow down the fermentation process.
Once the lid is on the jar, shake it well and set it up in a location no greater than 70 degrees Fahrenheit. Shake it well once or twice a day to try to remove the seeds from the gel. Open the jar at least once a day to “burp” it so that all gases from the fermentation process can escape. It may smell bad, but don't let that bother you. Do this for at least three days and up to a week.
At the end of the fermentation process, add about three times the amount of water to the glass, shake it again and let it sit for about an hour. Most of the viable seeds should fall to the bottom of the jar and the sticky layer of gelatin should float on the surface. Use a spoon to scoop up the gel layer and discard.
Pour off some excess mushy water, add fresh water, shake it, and repeat this last draining process again until the water looks mostly clear. Give it enough time each time to settle, with the viable seeds falling to the bottom and the non-viable ones floating, and scoop up the waste. As soon as the water is clear, empty the contents into a fine-mesh sieve and wash them off thoroughly.
If you use a lot of seeds, you can speed up the rinsing process by skimming off the original gel, placing the rest on a large sieve or in a large mesh sieve and spraying with a hard jet of water. The seeds won't get through the strainer or sieve, but any remaining residue will.
Some people choose to treat the semen at this point to prevent disease transmission. This step is optional, but recommended if you want to share seeds with others.
To treat the seed, make a 10% bleach solution (1 part bleach to 9 parts water) and let the seed soak for 30 minutes. Immediately return the seeds to the sieve and rinse under cold running water for at least 7 minutes. While doing this, stir or stir constantly to make sure they're completely rinsed off. Once you've rinsed for at least 7 minutes, continue drying.
Why seven to eight minutes of constant stirring under running water? Because this reduces the amount of residual chlorine in the bleach to below the National Organic Program threshold. Residual chlorine on the seed must be less than four ppm for the seed to be considered organic.
Ferment the seeds in their own juice.
How to dry tomato seeds
We need cool, well-ventilated conditions to dry out our tomato seeds. If it's too hot, like dehydrators or similar machines, it can boil the tomato seeds and make them sterile. This is the last thing we want!
You can leave your tomato seeds in a dry place. In this case, I recommend making a wooden drying frame out of some scrap wood and an old window pane. Attach the screen to the frame with a staple gun. You can then spread your seeds on top and store in a dry, well-ventilated place.
If you don't want to make a drying frame, you can put a piece of parchment paper on a baking sheet and place your seeds on top. This method takes a little longer to dry, but they will still dry out over time. Some people even use a paper plate for this, but with a paper plate they can stick to the surface and may be more difficult to remove. Since the parchment paper is more flexible, you should be able to bend it and immediately burst any stuck-on seeds.
Every day or two you need to come over and stir up your seeds to make sure they all dry out evenly. Break apart lumps that are stuck together with your fingers or rub them in your hands until they fall apart.
There is another method of drying seeds without heat. Use a box fan and two inexpensive air filters, plus some bungee cords. After the fermentation process is complete, store tomato seeds between these filters attached to the fan. The fan pushes cool air through the seeds and dries them out much faster than if they were just lying in a still air environment.
If you know how to save tomato seeds, you can grow them every year. Source: Kadluba
Saving tomato seeds without fermenting
It is possible to store tomato seeds without fermentation. At some point the gel coating crumbles by itself, which is why it is possible to plant a piece of shabby tomato and get sprouts. This method is ideal if you only have a few seeds to keep for yourself and you don't plan on treating the seeds to prevent the spread of disease.
For this method, you will need paper towels, tweezers, and a fresh tomato of your choice. Slice the tomato and scrape the seeds into a bowl. With your tweezers, pick up individual seeds along with their gelatinous goosebumps and press them onto the paper towel. Be careful not to clear them out. Put these paper towels in a dark, cool, and well-ventilated place to allow the seeds to dry out completely.
After drying, the seeds stick to the paper towel. You can fold the towel up and save it for later and even write the different seeds on the towel if needed. When it's time to plant next year, cut or tear off individual segments of towel and tomato seeds for planting. The paper towel will crumble and the seeds will germinate.
Please note that this method does not mean that you are reducing the chance of disease spreading. Because you include the dried gel in the seeds that have not been rinsed, there is little risk if one of your tomatoes has a potential disease. However, the risk is relatively small if you have been disease free.
The paper towel method is a non-fermenting seed saving method. Source: Coleypaulin
Long term storage
There are three words that apply to storing your tomato seeds: cold, dry and dark.
You don't need to freeze your seed as tomatoes don't need that much cold. But they like it cool in terms of temperature. Aim for a temperature range of 40 to 60 if possible, but don't panic, if your house is typically 70 degrees, that's fine too.
It is important to keep the seeds dry. Moisture is required for germination, and your tomato seeds will happily sprout in the dark if they have access to moisture. I like to keep mine in an airtight container in paper envelopes with a moisture-wicking silica packet.
Finally, the darkness also prevents early germination. While seeds don't need light to germinate, seeds that have access to heat and moisture can still do so. However, in the absence of moisture or heat, the darkness is ideal for long-term storage.
Check out our seed storage article for more in-depth tips on storing different types of seeds.
So, here are several ways to save tomato seeds. You can now start collecting tomato seeds from your favorite plants and continue the harvest year after year!
The green fingers behind this article:
Lorin Nielsen
Lifelong gardener
