Save seeds from ripe tomatoes in late summer, before frost kills the plant
The fastest way to save tomato seeds is to scoop them from a fully ripe tomato, ferment them in water for two to three days to remove the gel coating, rinse them clean, and dry them on a plate for two to three weeks. You can then store them in a paper envelope in a cool, dry place and plant them the following spring. The whole process takes about a month from harvest to storage.
Timing matters. Pick tomatoes for seed saving in late August or early September, while the plant is still alive and producing. If you wait until after frost has killed the plant, the seeds inside will not be viable. Choose tomatoes that are fully ripe — soft to the touch and deeply colored — because seeds from green or partially ripe fruit will not germinate well.
Not all tomato varieties will grow true from seed. Heirloom and open-pollinated tomatoes will produce plants identical to the parent plant. Hybrid tomatoes (usually labeled F1 on the seed packet) will not — the seeds will grow into plants that look different and often produce smaller or lower-quality fruit. If you saved seeds from a hybrid, you will get a surprise plant, not a copy of the original.
Key Takeaways
- Scoop seeds from fully ripe tomatoes, ferment them in water for two to three days, then rinse and dry them on a plate for two to three weeks.
- Save seeds only from heirloom or open-pollinated varieties if you want plants that match the parent tomato; hybrid seeds will not grow true.
- Pick tomatoes for seed saving while the plant is still alive, before frost arrives, because seeds from dead plants will not sprout.
- Store dried seeds in a paper envelope in a cool, dry place — a basement, closet, or unheated garage works well — and they will stay viable for three to four years.
Fermentation removes the gel coating that blocks germination
Each tomato seed is wrapped in a gel-like substance that prevents it from sprouting inside the fruit. You have to remove this coating, and fermentation is the easiest way. Cut a ripe tomato in half and squeeze the seeds and gel into a small jar or cup — do not add water yet. Let it sit at room temperature for two to three days. The seeds will sink to the bottom as the gel breaks down and mold grows on top.
After two to three days, fill the jar with water and stir. The mold and gel will float to the surface. Pour off the water and debris, then repeat this rinsing two or three more times until the water runs clear and the seeds feel slippery but not slimy. Spread the clean seeds on a paper plate or coffee filter in a single layer.
Do not use a plastic plate or paper towel — seeds stick to plastic and tear when you try to remove them, and paper towels absorb moisture and make seeds hard to separate. A ceramic plate or coffee filter lets air circulate and makes it straightforward to collect seeds once they are dry.
Drying takes two to three weeks in a warm, dry location
Place the plate of seeds in a warm room with low humidity — a kitchen counter away from direct sun, a basement, or a closet works well. Air temperature should be between 65 and 75 degrees Fahrenheit. Seeds are dry when they snap in half instead of bending, which usually takes two to three weeks depending on humidity in your home.
Do not use an oven or dehydrator, even on the lowest setting. Heat above 95 degrees Fahrenheit damages the seed's ability to sprout. If your home is very humid, place the plate in a room with a fan running, or move seeds to a dehumidified space like a basement or garage.
Once seeds are completely dry, store them in a paper envelope labeled with the tomato variety and the date you saved them. Do not use a plastic bag or sealed container — seeds need air circulation during storage, and moisture trapped in plastic will cause mold.
Storage conditions determine how long seeds remain viable
Tomato seeds stored in a cool, dry place will sprout for three to four years. The ideal storage temperature is between 50 and 70 degrees Fahrenheit with humidity below 50 percent. A basement, unheated garage, or cool closet is better than a warm kitchen or a humid bathroom.
If you want seeds to last longer, store them in the refrigerator or freezer. Place the sealed envelope inside a larger airtight container with a packet of silica gel or uncooked rice to absorb moisture. Seeds stored this way can remain viable for five to eight years. Let the container warm to room temperature before opening it, so condensation does not form on the seeds.
Check stored seeds once a year. If you see mold, discard them. If the envelope feels damp, move it to a drier location. Seeds that are properly stored and kept dry will not develop mold.
Cross-pollination can happen if you grow multiple tomato varieties
Tomato flowers pollinate themselves, so seeds from a single plant will be pure — they will not cross with other tomato varieties in your garden. However, if you grow two or more varieties very close together and bees visit the flowers, cross-pollination can occur. The resulting seeds may grow into plants with mixed traits.
To avoid this, save seeds from only one tomato variety per year, or space different varieties at least 10 feet apart. If you want to save seeds from multiple varieties, you can also cover the flowers with small bags before they open, remove the bags after the flower closes, and let the fruit develop without bee visits. This is more work but guarantees pure seeds.
For most home gardeners, growing one variety per year or accepting the possibility of mixed offspring is simpler than hand-pollinating. If you are saving seeds from an heirloom variety you want to preserve exactly, spacing and isolation matter more.
Tomato seeds from store-bought fruit usually will not grow
Seeds from supermarket tomatoes are often from hybrid plants, so they will not produce fruit identical to the parent. Additionally, commercial tomatoes are sometimes treated with fungicides or other chemicals that reduce germination rates. Seeds from farmers market tomatoes are more likely to be viable, especially if the grower is selling heirloom varieties.
If you want reliable seeds year after year, grow your own tomato plants from seed or seedlings, save seeds from the fruit, and replant them the following year. After the first year, you will have a supply of seeds adapted to your climate and growing conditions.
Frequently Asked Questions
Can I save seeds from cherry or grape tomatoes?
Yes, if they are heirloom or open-pollinated varieties. Follow the same fermentation and drying process. Cherry tomato seeds are smaller but viable. Check the seed packet or plant label to confirm the variety is not a hybrid.
What if I forget to ferment the seeds and dry them right away?
Seeds left in the gel for more than a few days may develop mold and lose viability. If this happens, rinse them thoroughly and dry them as quickly as possible in a warm, dry location. They may still sprout, but germination rates will be lower.
Do I need to label the seeds before storing them?
Yes. Write the tomato variety and the year on the envelope with a permanent marker. Without a label, you will not remember which seeds are which when you plant them months later.
Can I save seeds from a diseased tomato plant?
Seeds themselves do not carry most tomato diseases, so seeds from a diseased plant will usually grow healthy seedlings. However, if the plant had a fungal or bacterial disease, spores may be on the seed surface. Fermentation and rinsing reduce this risk significantly.
How many seeds does one tomato produce?
A single large tomato typically contains 150 to 300 seeds. One or two tomatoes will give you far more seeds than you need for a home garden. Save seeds from two or three tomatoes to have plenty for next year and to share with other gardeners.