Saving Your Home-grown Tomato Seeds

Fully ripe disease-free tomatoes are the best candidates for seed saving. Seeds can be saved casually, for example, by squeezing them onto a piece of paper towel and air drying them. Fermentation is a better option for long term storage and seed swapping. It removes germination inhibitors and the gelatinous sheath from seeds, and it may treat some seed-borne diseases. For long term storage and quick germination, fermentation is the trick.

Here’s the method:

Cut tomatoes open– one variety at a time– and squeeze the pulp, juice, and seeds into a glass or plastic container.

Fill the container halfway, but don't initially add water as a substitute for tomato juice if the mix is wet enough as water slows fermentation. In this current hot weather spell you may need to top up with a little bit of water just to prevent the seeds and pulp drying out altogether.

Label and set aside the containers for about three days in a warm spot, not in direct sunlight. Glass jars can be easily labelled with either a permanent marker or a white board marker as seen in the image above. Both wash off easily when finished with.

Two or three times daily, stir the fermenting juices to submerge the pulpy material. Give them a quick swirl around as you pass by! If you have a piece of light cloth that will cover the jars or containers but still let them breathe it is handy to keep out vinegar flies and other insects that might be attracted to the fermenting pulp.

After about four days, fill the container gently with water, stir, and pour off the pulpy water, scum and reject seeds on top. The seeds you want are the heavier, healthier ones lying at the bottom.

Repeat two or three times, and pour the seeds into a fine mesh sieve. Under running water, clean any remaining fruit jelly and debris from the seeds with your fingers.

Knock the strainer against the sink to remove excess water and quickly flip the strainer over, smacking it on a paper plate to deposit the seeds. Alternatively, scoop them out with a spoon and put them on a piece of grease proof paper. Label the paper with the variety and date.

Let the seeds dry for several weeks in a well-ventilated place at room temperature. The top of the fridge is ideal if you have an enclosed fridge space as the gentle heat dries the seeds.

Place dried seeds in paper packets, and then in an airtight container that’s stored in a dark, cool, dry place.