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.

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

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

Gather your 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 open0pollinated varieties ensures that the plants will exhibit the same traits as the tomato from which you harvest seed.

Cut the tomatoes in half width-wise to expose the seeds.

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

(Photo by Victor Schrager, courtesy of Amy Goldman

Squeeze the seeds and pulp into the container.

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 1/2 cup of non-chlorinated water to 1 cup of pulp.

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)

Once fermentation is complete, add waater 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.

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)

Spread the washed seeds thinly over coffee filters or paper plates to dry. Do not dry your seeds on paper towel or news paper 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 each step of the way.

(Photo by Victor Scrager, courtesy of Amy Goldman)

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.

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

And if you have questions or comments, be sure to 'Leave a comment' below.

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.