Saving tomato seed
Self-pollinating and annual, but the gel around the seed has to be fermented off or it will carry disease into storage. Once you know the fermentation step, it is straightforward.
- Life cycle
- Annual
- Pollination
- Self-pollinating
- Isolation
- 3–10 m
- Seed life
- 4–6 years
- Yield
- 1 fruit gives 50–100 seed
Tomato seed is enclosed in a gelatinous sac that inhibits germination and can carry fungal and bacterial disease from the fruit. In nature the fruit rots, the gel breaks down, and the seed survives. You are copying that process in a jar, which takes about three days and is the only fiddly part of saving tomato seed.
Tomatoes are self-pollinating — the flower releases pollen inside itself before it opens — so crossing is rare. Isolation of 3–10 m handles the occasional bumblebee.
The protocol
- 1
Choose a fruit past eating ripeness
Slightly over-ripe, even a little soft. Not rotten. Seed from a fully mature fruit germinates faster and more evenly than from a firm one.
- 2
Scoop into a jar
Cut the fruit across and squeeze or scoop the seed and gel into a small jar. Add about twice their volume of water.
- 3
Ferment three days
Leave the jar at room temperature, unstirred, for two to four days. A white mould will form on the surface. Stir once daily. Stop when the seed sinks and the pulp floats.
- 4
Rinse and dry
Pour off the pulp and mould, add fresh water, swirl and decant. Repeat until the seed is clean. Spread on a coffee filter or paper plate — not kitchen towel, which sticks — and dry for a week somewhere warm and dry.
- 5
Store cold
Sealed jar, silica, fridge. Viable four to six years, longer if frozen once fully dry.
What goes wrong
Skipping fermentation. Seed that is merely rinsed will germinate poorly and can carry the fruit's pathogens into next year.
Drying on kitchen paper. The seed welds itself to the paper and you end up cutting it out. Use a filter, a plate, or glass.
Save from a diseased fruit. Never save seed from a plant showing blight, mosaic or fruit rot. The pathogen goes with the seed.
Potato-leaf and other hybrids. If the variety is an F1 hybrid, the seed will not come true. Save from open-pollinated or heirloom varieties only.
Saved seed from this crop?
Germination rates, what came true and what crossed — post it and let other growers learn from it.
All 14 protocols
Annual, biennial and vegetative crops all save differently. The index compares them side by side.