After listening to Matthew Gammett talking about his way of letting his potato fruits ripen in a box for months until they’re basically rotting until he processes the seeds, I wonder whether the same could be done for tomato seed. Matthew, and others like @julia.dakin that have grown his seed, report that his seed germinate very fast. Perhaps because the rotting leaches out germination inhibitors.
My primary reason for wanting to do the same thing to tomatoes is convenience. These days, I go picking ripe or almost-ripe fruit from interesting tomato plants. I’d like to not have to process a lot of small batches. So if I could just let them be and continue to ripen on their own to the point of rotting, until I have enough to process them all in one go, I’d be happy. And if that helps germination in the other end, so much better.
Anyone here that does something similar or have related ideas?
Generally tomatoes store couple weeks after ripening. I just collect enough and then make patch to ferment. Just mark the date and what is there with tape, changes are that you’ll forget what there is or when you have put them there. I have forgotten some to plastic bags and can tell from experience that you don’t want to save seeds once they are rotting. It’s nasty, complicated and some seeds might spoil. Fermenting the gel will get rid of all those germination inhibitors.
The nasty part I can attest to as well. My hands have been stinking for days the years I have processed rotting tomatoes. The convenience makes it worth it for me. Do you know for a fact that the seeds spoil from being left to rot like this? That would persuade me to not do it.
You can save seed from tomatoes at the fully-ripe eating stage–all you need to ferment is the juice and seeds. I just squeeze my tomatoes into a jar on the counter when I cut them up for serving, making sauce, etc. Then rubber-band a piece of cloth to the top of the jar and leave it a couple of days. It is ready when there is a layer of white mold on top. Leaving it longer just invites disease organisms. In summer temps, it should take only 3 or 4 days. Really rotting–to where the white mold turns to brown goo-- is not necessary and may even be detrimental.
What you want is for the juice to ferment and become acid enough to dissolve the gel sac around each seed. When that is accomplished, add water and stir, pour off any solids, rinse in a strainer and dry the seeds on a plate or coffee filter.
That’s how it’s done by small seed companies. There’s no need to waste the fruits or put up with lots of nasty goop. When I stopped fermenting whole fruit and started squeezing out the seeds, seed-saving became much easier, because it’s the skins that are so hard to remove from the seeds at the end. If you exclude the skins at the beginning of the process, it becomes fast, easy, and much more do-able.
Just make sure the fruits are fully ripe. The color should be at it’s most saturated and intense, and the fruit should have softened to the touch. If it has cracked before fully ripe, it probably won’t be edible when fully ripe, but if the skin is intact, you should be able to use the tomato. More than once I’ve saved seed from tomatoes as I cut them up for cooking down into sauce, often with germination rates exceeding 90%.
What is your process for fermenting seeds that isn’t the whole fruit?
I slice the fruit in half and squeeze into a jar. It only takes a while when I have heaps of tomatoes to do. But each batch is quick. And I can still eat the fruit or make sauce.
Some seeds have been weird colour so I can’t say how good they have been. Everything has been sown in patches so cant say about the viability of those seeds. I would still worry about loosing part or most of the most important seeds. If you postpone, you can’t never say when you have more time and I have noticed that it’s easy to just keep on postponing. There should be enough time to make patches of ferment once in 1-2 weeks and the subsequent cleaning (which only takes few minutes even with bigger patches). Also I think you have to consider how many seeds some tomatoes have. If you have beefstakes that can have under 10 seeds per fruit, it’s a lot easier to look for them from whole ripe fruits. If you miss óut that some have little seeds, then you would be favouring fruits with more seeds.
I take the seeds out of the tomato fruit and I ferment them in small amount of water for 3-4 days. Then I rinse them and dry. My tomato seeds mostly germinate in anywhere from 1 to 3 days, I discard all that do not germinate in 7 days. That selection helped a lot with germination speed. I prefer eat the fruit or use otherwise in the kitchen, rather than let it rot for a long time.
If your tomatoes ripen over such a long period that you can’t process them all at once to extract the seeds, you can freeze them as the summer goes on, and then at the end of the summer, turn them all into tomato sauce, straining it to recover the seeds.
At that point, you can let them ferment in the traditional way for 3–4 days in a little water.
Has anyone tried avoiding fermenting tomato seeds altogether? I recall in the Endophytes Course that it was suggested to keep seed fermentation to a minimum, say a day or so, in an attempts to preserve some of the Endophytes. This year I have tried just straining my seeds, rinsing them well, and drying to store. I do notice the lil gel sac around the tomato seeds instead of the cute little hairs you usually notice after a few days fermentation and I’m hoping things won’t mold at all due to the extra material on the seeds themselves… I also understand that the whole fermentation process is to help dissolve the germination inhibitors but since I plant my tomato seeds in the late winter in a container with a domed lid, I would think that would dissolve any of those inhibitors and germinate successfully by the time temperatures are appropriate for sprouting. Previous years I always ferment for a few days, standard tomato seed saving practice. Been curious about this for a bit and didn’t want to start a new discussion about it. Hope someone has some insight!
I would caution against using water at the fermentation stage unless absolutely necessary, and then only a very small amount. In my 20 yrs in the seed trade, I’ve noticed it tends to impair germination.
One little-known thing about tomato seeds is that if they are not optimally mature at harvest, or they are fermented improperly, they often germinate fine the first year, but lose vigor more quickly than usual. When I started in the seed world, 10 year-old tomato seed could often germinate beautifully. Over the last few years I’ve found more and more batches that germinate in the 90% + range at first, but the next year they’re down to 70% or less. I couldn’t understand it until I talked to an old hand, one of the pioneers of organic seed. He said that maturity of the tomato–very soft and deeply colored–made a big difference in how long the seed could maintain vigor. Another factor in maintaining vigor is nutrition. Adequate potassium helps seed longevity greatly.
If a tomato ripens and falls on the ground it’s going to ferment for at least a week, assuming nothing bites into it. And even then, a fruit will lay and ferment and break down.
That’s how nature would handle it. My question on the idea is then, how does the plant more successfully pass on endophytes to the seeds without that happening? Surely being digested and deposited in a turd isn’t any easier on endophytes?
I’m doing that for 20 years as well, works great. My seeds germinate in 1-3 days. Possibly as always, details matter.
I have germinated the seeds from one variety, collected every year since 2013 to 2025, same way. ALL of them had a good germination rate.
Currently, my tomato seed collection dates back to 2013 as well (but not all years are represented for each variety), and all seeds I have collected are still viable, while seeds purchased from renowned breeders (not companies) fail to germinate as you have described, 30% per year or faster. This applies to some well known European sellers, unfortunately. For this particular reason I have stopped adding new varieties and I rely only on my own seeds since 2024. I have 99% germination rate within 7 days or less (I discard everything that is not germinating in 7 days).
Ive certainly seen tomatoe seed rot in such a situation, but also seen seed that survived, feels to me that would be another selection pressure? Also seems that selection pressure would work well with wanting tomatoes that volunteer in the fields, as seeds that survive the rotting, may also survive it better outside. The smell would defiantly persuade me not too, but if you could just smash all the rotten tomatoes in a jar and process the same way you do when ya purposely ferment them, by filling with water and pouring out, perhaps you’d avoid the stinky hands that way, but as someone mentioned above it is annoying have whole tomatoe pieces in the liquid, though i often do that for cherrys.
In an unintentional experiment, it took about 8 days for a forgotten paper bag of cherry tomatoes to ferment enough to burst the skins and soak the bag. Causing me to notice and take care of them just now… That’s inside at 70-76°F.
That’s inside at 70-76°F.