How do you save tomato seeds? Saving tomato seeds takes about a week. Pick a fully ripe fruit from an open-pollinated plant, scoop the seeds and gel into a jar with water, ferment for 2 to 5 days, rinse off floaters, dry seeds on a screen and store them cool and airtight, per UC, UVM and Organic Seed Alliance.
Key takeaway: Use open-pollinated fruit, ferment 2 to 5 days, rinse, dry fully, then store cool, dry and labeled.
| Step | What to do | Source |
|---|---|---|
| 1. Choose | Fully ripe fruit from a healthy open-pollinated plant | UC Master Gardeners, UVM |
| 2. Scoop | Seeds and gel into a labeled jar, add a little water | UC Master Gardeners |
| 3. Ferment | 48 hours to 5 days at 70 to 85°F (21 to 29°C) | OSA, UVM |
| 4. Rinse | Decant pulp and floating seeds, keep sinkers | OSA, UVM |
| 5. Dry | Single layer on a screen or paper plate, under 95°F (35°C) | OSA, UC |
| 6. Store | Airtight, cool, dry, labeled with variety and date | UC, UVM |
Which Varieties Are Best for Saving Tomato Seeds?
Open-pollinated and heirloom types only. UC Master Gardeners of Santa Clara County explain that all heirlooms are open-pollinated and come true from seed, while hybrids do not breed true. Organic Seed Alliance (OSA) adds that seed from an F1 hybrid will grow but produce variable plants. Check the packet or catalog before saving tomato seeds.
If you grow compact plants indoors, see our guide to micro dwarf tomatoes for small open-pollinated options.
How Do You Pick Fruit When Saving Tomato Seeds?
Saving tomato seeds starts with the best plant, not leftovers. UC Master Gardeners advise taking fruit in its prime from your healthiest, most productive plant, and avoiding diseased, misshapen, overripe or underripe fruit. Save from several fruits and, if possible, more than one plant of the variety to keep genetic diversity. UVM Extension says to harvest fruit when fully ripe.
Why Does Saving Tomato Seeds Need Fermentation?
Fermentation removes the gel. OSA says the gel around each seed contains germination-inhibiting compounds, and fermentation breaks it down so seeds rinse clean. It can also reduce some diseases on the seed coat, though not infections inside the seed. UC Master Gardeners say fermenting is optional but helps sort bad seeds and is good etiquette when trading.
How Do You Ferment Tomato Seeds Step by Step?
Use a jar and a few days. For saving tomato seeds, UC Master Gardeners suggest cutting the fruit, scooping seeds and gel into a labeled container, and adding 1/4 to 1/2 cup (60 to 120 mL) of water. Keep it out of the sun. OSA recommends 70 to 85°F (21 to 29°C) and stirring two or three times a day.
- Cut the tomato and squeeze seeds and gel into a jar.
- Add a little water and label the jar with the variety.
- Stir daily; a thin white mold on top is harmless.
- Stop when seeds sink and pulp floats, before any sprout.
How Long Does Tomato Seed Fermentation Take?
About 2 to 5 days. OSA reports fermentation takes 48 to 72 hours depending on temperature and variety, while UC Master Gardeners suggest 3 to 5 days and UVM Extension stirs twice a day for five days. Watch closely: OSA warns that sprouting seeds mean they soaked too long and damage has already occurred.
How Do You Rinse and Dry Seeds When Saving Tomato Seeds?
Decant, then dry on a screen. For saving tomato seeds, OSA suggests about 1 part slurry to 4 parts water, letting good heavy seeds sink while pulp and light seeds are poured off. UVM says floating seeds are non-viable. Spread seeds thinly on a screen, coffee filter or paper plate, not plastic or ceramic, and keep them below 95°F (35°C).
Before sowing your saved seed, review our hydroponic germination methods to start them in plugs or cubes.
What Is the Best Storage for Saving Tomato Seeds?
Cool, dry and airtight. UC Master Gardeners say fully dry seeds stay viable for years even at room temperature, and the fridge or freezer adds protection if you warm the jar before opening. OSA gives a rule of thumb: relative humidity (percent) plus temperature (°F) should total 100 or less. Store seeds in glass or metal, since mice like them.
Does Cross-Pollination Affect Saving Tomato Seeds?
Sometimes. Tomatoes mostly self-pollinate, but OSA recommends 10 feet (3 m) between modern varieties and 40 feet (12 m) between heirloom or potato-leaf types for home seed, because their stigmas extend past the anther cone. UC Master Gardeners suggest bagging unopened flower clusters with paper or cloth, then tagging that truss for heirloom seed.
FAQ About Saving Tomato Seeds
Is saving tomato seeds from store-bought fruit worth it?
Only if the variety is open-pollinated; most are hybrids that will not breed true.
Do I have to ferment the seeds?
No. UC says it is optional, but OSA says it removes the germination-inhibiting gel.
Why did some seeds float?
UVM Extension says floating seeds are non-viable, so discard them.
How many plants should I use for saving tomato seeds?
OSA suggests 10 to 20 plants to maintain a variety long term.
If my seeds fail to sprout, what then?
See our guide to hydroponic seeds not germinating.
Sources
- UC Master Gardeners of Santa Clara County — Saving Tomato Seeds (PDF)
- Organic Seed Alliance — Tomato Seed Production Guide
- University of Vermont Extension, Amy Simone — Saving Seeds from Vegetable Crops
- Photo credits (Wikimedia Commons, edited with titles): Solanum lycopersicum Bohun 2022-08-26 9218 by Salicyna (CC BY-SA 4.0); A Slice Of Tomato – Flickr – Lisa Zins by Lisa Zins (CC BY 2.0); Heirloom tomatoes at county fair by Eric Polk (CC BY-SA 4.0); Pepper and tomato seedling trays at Boğaziçi University 2026 by Furkan Akkurt (CC BY-SA 4.0)