How-to Guide
How to Save Tomato Seeds by Fermentation
The short answer
Scoop the seeds and their surrounding gel from a fully ripe tomato into a jar with a little water, then let it ferment a few days, stirring once or twice daily. Fermentation breaks down the gel coat and destroys many seed-borne diseases; viable seeds sink to the bottom, usually within about five days.
Pour off the floating debris and bad seeds, rinse the good seeds that settled, and spread them on a fine sieve or cheesecloth to dry fully before storage. Save seed only from open-pollinated or heirloom varieties, since hybrids will not come true.
Ferment and separate
- 1Scoop seeds and gel — Take seeds and the gel around them from a fully ripe tomato and put them in a jar with some water.
- 2Ferment a few days — Stir or swirl once or twice a day at room temperature; viable seeds sink within about five days.
- 3Rinse and decant — Pour off floating seeds and liquid, add fresh water, and repeat until the sunken good seeds are clean.
- 4Dry thoroughly — Spread seeds on a fine sieve or cheesecloth and dry until they are hard and snap rather than bend.
Store the dried seed
Once fully dry, keep seeds in a cool, dry, dark place in labeled envelopes or jars. See the seed-storage guide for longevity.
✔ Fermentation matters because it removes the germination-inhibiting gel and reduces many seed-borne diseases carried to next year's plants.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Saving vegetable seeds — Ferment tomato seeds and gel in water; viable seeds sink; save from open-pollinated varieties.
- Oregon State University Extension — A step-by-step guide to saving seeds (EM 9663) — Fermentation destroys seed-borne diseases; rinse sunken seeds and dry on cheesecloth or sieve.
- Penn State Extension — Saving Seeds from Your Garden — Stir the fermenting mixture daily for several days until seeds settle, then dry until brittle.