How to Save Heirloom Tomato Seeds

Heirloom tomatoes are the highlight of summer—beautiful colors and bountiful flavors! Preserve the bounty for next year by saving seed of your favorite tomato varieties. You only need a few fruit to get started, so watch the slideshow below and learn how. By doing so you’ll carry on a gardening tradition that is many generations old.

For even more tomato seed saving information, register for our Tomato Seed Saving Webinar. And if you have questions or comments, be sure to ‘Leave a comment’ below.

decomposing tomatoes

In nature, ripe tomatoes fall from the plant and slowly rot, allowing natural weathering to break down the gelatinous coating on the seed.

ripe tomatoes

To speed up this process, seed savers must deliberately remove the coating from the tomato seed through the process of fermentation. Here’s how.

colored tomatoes

Gather supplies. You’ll need a clear container, a kitchen strainer, a drying substrate, and some of your best open-pollinated tomatoes. Saving seed from heirloom or open-pollinated varieties ensures that the plants will exhibit the same traits as the the tomato from which you harvest seed.

saving tomato seeds

Cut the tomatoes in half widthwise to expose the seeds.

saving tomato seeds

With smaller varieties, cut an ‘X’ into the bottom of the fruit.

(Photo by Victor Schrager, courtesy of Amy Goldman)

savng tomato seeds

Squeeze the seeds and pulp into the container.

saving tomato seeds

There is no need to add extra water to the container unless the liquid from the tomato evaporates before fermentation finishes. If you need to add water, use ½ cup of non-chlorinated water to 1 cup of pulp.

saving tomato seeds

Place the container in a location where it will be undisturbed for 1-4 days (and where you won’t mind the smell!). Fermentation time depends on air temperature, humidity level, and ripeness of fruit. As the tomato pulp ferments, a layer of white mold may grow across the top. Don’t be alarmed—this is natural. Tomato seeds have finished fermenting when the gelatinous seed coats float to the surface of the liquid.

(Photo by Victor Schrager, courtesy of Amy Goldman)

saving tomato seeds

Once fermentation is complete, add water to the mixture and stir. Mature seeds will sink to the bottom of the container. Save these seeds. Any seeds that float are not mature or viable, so don’t save these seeds. Pour the pulpy mixture out of the container, making sure to leave the viable seed at the bottom.

saving tomato seeds

Pour the remaining liquid and seeds into a kitchen strainer and wash the seeds thoroughly under running water.

(Photo by Victor Schrager, courtesy of Amy Goldman)

saving tomato seeds

Spread the washed seeds thinly over coffee filters or paper plates to dry. Do not dry your seeds on paper towels or newspaper, as the seeds will stick to the paper when dry. Keep seeds out of direct sunlight, and allow up to four weeks for seeds to dry fully. And remember—label everything every step of the way.

(Photo by Victor Schrager, courtesy of Amy Goldman)

saving tomato seeds

Placing the seeds in front of a fan will help them dry faster. Seeds are fully dry when they easily crack in half when bitten into or bent.

saving tomato seeds

Store the dried seeds in an airtight container in a dry, cool, and dark location.


Note from a seed saver: Tomatoes will usually self-pollinate, so seeds saved should remain ‘true-to-type’ without worries about cross-pollination. However, there are always exceptions. Some tomatoes can cross-pollinate, which depends on many factors such as flower shape, environment, and pollinator activity. To ensure seed purity you may want to plant only one variety of tomato, or spread different varieties throughout your garden.

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  1. Can blight be spread through seeds to the next year’s crop? Should those seeds just be discarded?

    • Christy, Seed Savers Exchange says:

      Hello Amy!
      Blight can be spread through seeds into the next year’s crop. There are a few steps you can take to remove the blight inoculum from the seeds so that you don’t have to discard them. Take a look at this webpage from the Ohio State University Extension that discusses different methods on treating seed, such as hot water and bleach. ( The bleach method is probably your best bet – hot water treatments must have specific temperatures to prevent accidental cooking of the seed.
      Hope that helps, and keep posting if you have any other questions!

  2. This was incredibly helpful – Appreciate the details

  3. Thanks for the tips! Will you do a post or webinar on how to grow the seeds indoors that we saved from last year? That is where I seem to fail miserably every year.

  4. jerry (verdi) aka mr. greenjeans says:

    I also found the tomatoe seed process most helpful. I will add though, it helped me to be more precise to have come from my old chemistry class back in the late 60′s.
    As far as ‘ the process’ mentioned, I always try to use the ripest fruit so to know that the fruit has ‘ turned the corner’ on its biologics. Though I didn’t allow the fermentation process(and will next time because I see that it is most relevant ), I did soak the seed in an luke warm*** organic soapy solution for just a few minutes, and then of course, rinse thoroughly. This may have taken care of the glutenous material around the seeds because most if not all of my seeds made it this year. It also allows the seeds to separate easily from the same gooey material that binds them as they dry. I also (by accident but not really) used one of those styrofoam type camping/paper plates (because it was all I had at the time) and it really made a difference when the seeds became dried as they did not stick to either the plate or themselves and separated individually. Of course though, I don’t use these plates for anything else these days as they are an oil by product and should not find their way into the system as they do not decompose. But paper plates and paper towels are brutal because the seed wants to adhere( unless the paper plate has a wax lining ??). Anyway….. nice to see such devotion here from this site members. i will also add as a side note, look up on u-tube presentations the recent study on lab rats by a French bio-lab on GMO’s and Monsanto and of course, prop.37 here in California on labeling of foods. Monsanto is spending alot of cash on disinformation and they just might be working with the Dept. of HomeLand Security(for Der the Reich Land) lol lol. Therefore …….
    “Keep your nose to the wind and your eyes on the skyline Jeremiah”.

  5. LindaPitts says:

    is have one tomato plant growing inside our basement with plenty of light/
    Usually [ this year also] plant the Cherry Tomatoes as they seem to adjust to the basement conditions well over Winter.
    I also make sure some Gnats are in the area the plant is in[ they pollinate the plant] too many eat them so I keep the Gnats low population.
    The Gnats do what the Bees do outside but on a smaller scale and has worked for me for many years.
    Usually in Feb/March following Winter indoors the tomatoes do have a few Tomatoes and they are as good as grown outside but way fewer.

    • Actually, tomatoes don’t need gnats or bees to pollinate. They’ll pollinate themselves! Because gnats can spread disease and cause problems with ripening fruit, I’d recommend not worrying about gnats in the future. Glad to see you can grow tomatoes during the winter – I haven’t tried yet!