Fermenting and saving tomato seeds
Garden of Eatin', Seeds & Seedlings

Fermenting and Saving Tomato Seeds

I’ve talked about fermentation quite a bit on this blog, from fermenting your cabbage to fermenting your chicken feed. In a nutshell, fermentation is the process of good bacteria breaking down the structure of your food so that it becomes more digestible.

When it comes to fermenting chicken feed, for instance, lacto-fermentation reduces the anti-nutrients found in the outer layers of all grains, seeds and legumes. These anti-nutrients are in place to protect the grain (or seed or legume) until it germinates.

That means every seed you save from your plants comes with a survival mechanism that helps keep it viable until the proper growing conditions are present. This is especially true of “wet” seeds from tomatoes (as well as cucumbers, melons and squash) which are covered with an extra protective layer on the seed coat.

These wet seeds benefit from the simple process of lacto-fermentation before being washed, dried and stored. In the outside world, tomato seeds naturally ferment when over-ripe tomatoes drop from their vines and rot in the ground, where bacteria are actively working. When we manually collect seeds from tomatoes, it’s a fine idea to ferment them ourselves.

Lacto-fermentation removes the germination-inhibiting substance on the seed coat, that gooey gel sac that surrounds each seed. Fermenting also kills certain seed-borne diseases (as good bacteria overtakes bad bacteria), which promotes the health of seedlings and the vigor of mature plants.

During fermentation, bad seeds generally float to the surface of the water while good, viable seeds sink to the bottom. It has also been said that properly fermented, washed, dried, and stored tomato seeds can last up to 10 years! Talk about passing down a true heirloom to your kids.

In case you’re wondering, you do not need to ferment tomato seeds. Non-fermented seeds have sprouted just fine for me… and they also have not. Often it is a matter of luck and genetics. But if you can increase your chances of germination, have it happen much sooner in less than ideal conditions, and improve the health of your future plant, fermentation is too easy not to try.

To begin fermenting, squeeze or scoop the seeds (with accompanying gooey stuff) out of fully ripe tomatoes into a clean, small jar. There’s no need to separate the seeds, but do try to remove as much of the pulp as possible.

Fully ripe tomatoes with lots of seeds

Scoop tomato seeds into a clean jar

Cover the seeds completely with at least an inch of dechlorinated (or filtered) water and loosely place a lid over the jar while the whole thing is brewing. Do not seal the jar tight, as you want to leave some airflow for the fermentation gases to escape.

Loosely seal the lid with a jar and leave at room temperature

Within a day or two (more or less, depending on your room temperature; warmer ferments quicker), a frothy white film will start to form on the surface of the water. It will smell slightly sour, like yogurt. This is lacto-fermentation in action, and while it doesn’t look like anything significant is happening, it’s a sign of your potential new seedlings and next year’s salsa.

Lacto-fermentation at work

Once the film has covered the whole surface (in another day or so), it’s time to wash away all that scum. Quickly pour off the top layer of water (with the frothy stuff and bad seeds) so all that remain are your good seeds at the bottom.

Wash the seeds as you normally would, under running water in a fine mesh sieve. You can gently rub the seeds against the mesh to remove any sticky remnants.

Wash the seeds under running water

Spread the seeds out on a paper towel and pat them down to absorb most of the moisture, then transfer to a non-porous surface (like a dish) to finish drying completely. After a few days, store the seeds in a labeled and dated envelope in a cool, dark place. Your seeds are now ready for sowing!

Dry the seeds on a non-porous surface

For more on seed saving, check out my post on collecting and saving seeds.

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