How to Ferment Tomato Seeds

Saving seed from your best tomatoes is easy but requires fermentation first.

Tomato seeds must ferment before they will germinate. Fermentation removes the gelatinous sack that encases each tomato seed. The gelatinous sack contains chemicals that inhibit germination, preventing seeds from sprouting inside the tomato fruit. When tomatoes fall to the ground and rot, fermentation occurs naturally and the seeds will sprout the following spring. To save tomato seed to grow next season, you must simulate the fermentation process. Fermentation also kills some tomato diseases that are borne by the seed.

Things You'll Need

• Ripe tomatoes
• Sharp knife
• Glass jar
• Spoon or stick
• Fine mesh strainer
• Glass plates
• Paper or plastic storage bags or containers
• Marking pen

Instructions

Fermenting Seeds

1. Choose tomatoes that are fully ripe and have the best characteristics for their variety. Slice the tomato in half across the middle. Squeeze the seeds and juice into a clean glass jar. You can also scoop seeds from a tomato you are slicing for immediate consumption into a jar. Add water if the seeds are not covered in their own juice.

2. Label the container with the tomato variety and year of harvest. Place the container where children or pets will not disturb it. Choose a location where the smell will not bother you, such as a garage, greenhouse or outdoors.

3. Allow container to remain at room temperature until a layer of fungus has grown across the surface. Fermentation will happen within one to three days at temperatures of 70 to 80 degrees F. At cooler temperatures, the fermentation process could take a week.

After Fermentation

1. Remove seeds from the water when fermentation is complete. Add water to double the mixture. Stir vigorously. Good seeds will settle to the bottom of the jar.

2. Pour off the water. Pour out floating hollow seeds, mold and any debris with the water.

3. Add water. Pour off the water and hollow seeds again. Repeat this process until only clean seeds remain.

Drying Seeds

1. Strain the clean seeds to remove excess water. Spread out the seeds on a glass or ceramic dish to dry. Blot excess water if it pools on the dish.

2. Place in a warm, dry, ventilated location away from direct sunlight. Do not dry the seeds in an oven. Turn the seeds at least twice daily, making sure they do not touch one another. Let dry for one to three weeks, depending on your climate.

3. Store fully dried seeds in glass jars, plastic bags or containers. Label the containers with the variety and year of seed harvest. Store in a cool, dry place or in the freezer.

Tips & Warnings

• Work with one tomato variety at a time.

• At cooler temperatures, fermentation will take a few days longer.

• Don't let tomatoes sit in water for too long after fermentation has begun or they could sprout.

• Don't spread the tomato seeds on paper towels or paper plates to dry. The seeds will stick to the paper.

• If the seeds are not completely dry before storing, they will mold. Remove seeds immediately if you see signs of dampness or mold. Discard damaged seeds. Allow good seeds to dry further.

References

• "Seed to Seed"; Suzanne Ashworth; 2002
• Tomato Dirt: How to Save Tomato Seeds to Plant Next Year