Tomato seeds keep well. Stored cool and dry, they often sprout for four to six years and sometimes longer, though the germination rate slowly falls with age. Enter how old your seeds are and how they were stored to see roughly what germination to expect and whether to sow extra.
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What Your Result Means: the percentage is a rough guide to how many of your seeds may still sprout, based on age and storage. Old seeds are not wasted, you just sow a few more to make up for lower germination, or run a quick paper-towel test first.
Are Old Tomato Seeds Still Good?
Usually yes, for several years. Enter the age of your seeds and how they were stored, and the tool estimates the germination you can expect and whether to sow extra or test a sample first.
- Enter the Seed Age, the years since the packet was dated or since you saved them.
- Choose the Storage, cool and dry, room temperature, or warm and humid.
- Read the Estimate, then sow as normal, sow extra, or run a germination test.
What Each Result Means
| Result | What It Tells You |
|---|---|
| Germination estimate | Rough share of seeds likely to sprout |
| Verdict | Whether to sow as normal, sow extra, or test |
| Sow this many | Seeds to sow for about 10 plants |
Viability by Age
Estimated germination for tomato seeds kept cool and dry, from a simple decline model rather than measured data. Poor storage shortens these figures.
| Seed Age | Typical Germination | What to Do |
|---|---|---|
| 0 to 1 year | 85 to 95% | Sow as normal |
| 2 to 3 years | 80 to 85% | Sow as normal |
| 4 to 5 years | 60 to 70% | Sow as normal at 4 years; a few extra at 5 |
| 6 to 7 years | 40 to 50% | Sow extra or test |
| 8 years or more | 30% or less | Test a sample first; replace if under about 25% |
How Does the Estimate Work?
The tool starts from a typical germination curve for well-stored tomato seeds, then adds effective age for warmer or damper storage, since heat and moisture age seeds faster.
Storage adjustment: cool and dry adds 0 years, room temperature adds 1, warm or humid adds 3
Seeds to sow for 10 plants = 10 divided by the germination rate, rounded up
Cool, dry, dark storage is what keeps tomato seeds alive for years. Warmth and humidity are the two things that shorten their life the most.
Worked Example
Say you have 5-year-old seeds stored at room temperature. That counts as about 6 effective years, so the tool estimates roughly 48% germination and suggests sowing a few extra: about 21 seeds to get 10 plants. Kept cool and dry instead, the same seeds would sit near 60% and need about 17.
Factors That Change Viability
- Storage temperature: cool storage, even a fridge, greatly extends seed life; heat shortens it.
- Moisture: damp seeds age fast and can mold, so keep them dry, ideally sealed with a desiccant.
- Original quality: well-ripened, well-dried seed lasts longer than seed saved from unripe fruit.
- Light and air: darkness and a sealed container slow aging.
- Seed to seed variation: a packet is an average, so a quick test beats a guess for old seed.
Understanding Your Outputs
| Output | Meaning | Best Used For |
|---|---|---|
| Germination estimate | Share likely to sprout | Judging if seeds are worth sowing |
| Verdict | Normal, extra, or test | Deciding your next step |
| Seeds to sow | Count for 10 plants | Sowing enough to hit your goal |
When to Use It
Use it before sowing seeds you saved or bought a few years ago, or when deciding whether to buy fresh. Pair it with the germination calculator for timing and the plants needed calculator for how many to grow.
Common Mistakes to Avoid
- Tossing old seed: tomato seeds often sprout for years; test before you throw them out.
- Storing warm and damp: a hot shed or garage ages seeds quickly, so keep them cool and dry.
- Sowing the same as fresh: for old seed, sow extra and thin the seedlings later.
- Skipping a test: a paper-towel test takes a week and settles the question for old seed.
- Ignoring the date: mark packets with the year so you know their age next season.
Accuracy and Limitations
These are typical germination figures, not a measurement of your exact seeds.
What It Estimates: a reasonable germination range from seed age and storage.
What It Cannot Know: your seeds’ original quality or exact conditions. For old or valuable seed, a paper-towel germination test gives the real answer.
Methodology
Method: a typical tomato germination-by-age curve, adjusted for storage, gives an estimated germination rate and a sowing recommendation. Inputs Used: seed age in years and storage condition. Curve: an estimated decline model, not measured data, built around the typical 4 to 6 year life of well-stored tomato seed: about 95% when new, 85% at 2 to 3 years, 65% at 4 to 5, 45% at 6 to 7, and under 30% by 8 or more, for cool, dry storage. Storage: adds 0 effective years for cool and dry, 1 for room temperature, and 3 for warm or humid. Sowing: seeds for 10 plants equals 10 divided by the germination rate, rounded up. Note: a paper-towel test measures your actual seeds.
Sources: Iowa State University Extension – Growing Tomatoes, The Old Farmer’s Almanac – Tomatoes, Royal Horticultural Society – Tomatoes. Last reviewed: September 26, 2026 · Reviewed by Aiza Anwar.
Frequently Asked Questions
How long do tomato seeds last?
Stored cool and dry, tomato seeds usually stay viable for four to six years and often longer. Germination slowly falls with age, so older seed sprouts less reliably.
Are old tomato seeds still good?
Often yes. Seeds a few years old commonly sprout well, though at a lower rate. Sow a few extra to make up for it, or run a quick germination test first.
How can I test old tomato seeds?
Fold 10 seeds in a damp paper towel, seal it in a bag somewhere warm, and check after 5 to 10 days. The number that sprout out of 10 is roughly your germination percentage.
How should I store tomato seeds?
Keep them cool, dry, and dark in a sealed container, ideally with a desiccant. A fridge is excellent. Heat and humidity are what shorten seed life the most.
Can I store tomato seeds in the fridge?
Yes. A sealed, moisture-proof container in the fridge keeps tomato seeds viable for many years. Let the container warm to room temperature before opening to avoid condensation.
Do older seeds sprout more slowly?
Often, yes. Older seeds may take a little longer and sprout less evenly, so give them the ideal warm, moist conditions and a bit more patience.
Should I sow more of an old seed packet?
Yes. Sow extra in proportion to the lower germination, then thin the seedlings to the strongest ones once they are up.
How can you tell if tomato seeds are bad?
Age and storage are the best clues, since tomato seeds do not change much in appearance. A paper-towel germination test is the reliable way to know.
Do tomato seeds need to be dried before storage?
Yes. Saved seeds must be fully dry before storing, or they will mold and lose viability. Dry them on a plate or screen for a week or two first.
Related Tomato Tools
Time Sowing with the Germination Calculator
This tool gives typical germination estimates from seed age and storage, not a measurement of your exact seeds. Original quality and conditions vary. For old or valuable seed, run a paper-towel germination test for the real rate. Spotted an error? Tell us here.