To save tomato seeds, scoop the seeds and gel from a ripe open-pollinated tomato into a jar with a little water. Let it ferment for a few days, stirring daily. Pour off the floating pulp, rinse the seeds that sank, and dry them fully. Store them in a cool, dry, dark place for next season.
On this page
Tomatoes are one of the best first crops for seed saving. University of Illinois Extension lists them among the easy annual, self-pollinating crops that need only a few plants to give good seed. The fermentation step looks strange the first time, but it’s simple.
Choose the right tomatoes
- Open-pollinated or heirloom only. F1 hybrid tomatoes won’t grow true from saved seed. Check the seed packet or plant tag. Our guide to heirloom seeds explains the labels.
- Pick your best plant. Choose healthy, productive plants with fruit typical of the variety. Over the years this selection shapes your strain.
- Let fruit ripen fully. University of Minnesota Extension says to let fruit ripen fully before scooping the seeds.
Why ferment tomato seeds?
Each tomato seed sits in a gel sac. Fermenting the seed in water for a few days breaks that coating down. Illinois Extension notes that viable seeds sink while pulp and poor seed float, which makes cleaning easy. Minnesota Extension says seeds should sink to the bottom within five days.
Expect a smell and a layer of mold on top. That’s normal. Keep the jar somewhere it won’t bother anyone, and label each jar if you’re saving several varieties.
Tip: Don’t leave seeds fermenting much longer than needed. Once most seeds have sunk, move on to rinsing so they don’t start to sprout in the jar.
How to dry and store tomato seeds
Spread rinsed seeds in a single layer on a ceramic plate, a glass dish or a fine screen. Paper towels work, but seeds stick to them. Stir or break up clumps daily, and let them dry completely before storing. Seeds that still feel damp can mold in storage.
For storage, Illinois Extension recommends paper envelopes, with a glass jar for pest-proof long-term storage. Label each one with the variety and date. Minnesota Extension recommends tightly sealed glass containers kept between 32°F and 41°F, so a refrigerator works. A silica gel packet or a little powdered milk wrapped in tissue will absorb moisture.
How long do tomato seeds stay viable?
Stored cool and dry, tomato seed lasts several years. A seed viability chart from UC Master Gardeners of Nevada County lists tomatoes at 3–7 years. Germination declines with age. University of Minnesota Extension advises using saved seed within a year for best results, because older seed has lower germination and vigor.
To check older seed, do a simple germination test. Roll a counted handful of seeds in a damp paper towel, keep it warm, and count how many sprout. If only some of them sprout, sow more thickly to make up for it.
Cross-pollination: do tomatoes cross?
Mostly not, but sometimes. Tomatoes are largely self-pollinating, and the Seed Savers Exchange isolation chart reproduced by Illinois Extension lists them as “self or insect” pollinated. It recommends 10–50 feet between tomato varieties for seed saving. In a home garden, practical steps are:
- Leave a few feet and another crop between varieties you plan to save.
- Save from fruit in the middle of the plant, not the end next to another variety.
- If you need to be certain, cover a flower cluster with a fine mesh bag before it opens, and tag the fruit that sets.
Most gardeners saving a couple of varieties get seed that grows true with modest spacing. If an odd plant appears next year, don’t save its seed.
What’s next
Tomatoes are a good gateway. Seed saving basics covers beans, peas and lettuce, all easy, plus the crops that need more isolation. For the bigger picture, start at homesteading for beginners. To put up the rest of your tomato harvest safely, see the pantry hub.
The project
How to Save Tomato Seeds (Fermentation Method)
- Prep20 min
- Cook72 hr
- Total72 hr 20 min
- MakesSeeds for next season
You'll need
- 2–3 fully ripe tomatoes from a healthy open-pollinated or heirloom plant
- Water
- 1 small glass jar or cup per variety
- Masking tape and a marker for labels
- A fine sieve
- A ceramic plate, glass dish or fine screen for drying
- Paper envelopes and an airtight glass jar for storage
Steps
- Pick fully ripe fruit from your healthiest, most typical plant of an open-pollinated variety.
- Cut each tomato across its middle and squeeze or scoop the seeds and gel into a labeled jar.
- Add a small amount of water and stir.
- Set the jar somewhere warm, out of direct sun, and stir once or twice a day for 2–4 days.
- When a layer of mold forms and the seeds have sunk, pour off the floating pulp, mold and seeds.
- Rinse the sunken seeds in a sieve under running water until clean.
- Spread the seeds in a single layer on a ceramic plate, glass dish or screen to dry, stirring daily so they don't clump.
- When fully dry, store the seeds in a labeled paper envelope inside an airtight jar somewhere cool, dark and dry.
Questions people ask
Do you have to ferment tomato seeds?
It's the standard method recommended by extension services. Fermentation breaks down the gel coating around each seed and helps separate viable seeds, which sink, from pulp and poor seed, which float.
How long do saved tomato seeds last?
A seed viability chart from UC Master Gardeners of Nevada County lists tomato seed at 3–7 years when stored well. University of Minnesota Extension advises using saved seed within a year for best germination and vigor.
Can I save seeds from a store-bought tomato?
You can try, but many supermarket tomatoes are F1 hybrids, so the plants may not match the fruit. An heirloom from a farmers market or your own garden is a better bet.
Why did my fermenting tomato seeds grow mold?
A layer of white or gray mold on top is a normal part of fermentation. Skim it off with the floating pulp and rinse the seeds that sank.