Seed Viability & What's Left After Storage
Tests wheat
Enter initial germination, the annual decline rate and years stored to get the current viability — so you know whether to raise the seed rate or replace the lot.
Check stored-seed viability
Next: viability is marginal (69.3%) — run a quick germination test and increase your seeding rate to compensate.
Real decline depends on species, moisture and storage temperature; cool, dry storage slows the rate well below the figure entered here.
Seed viability — key facts
- Formula
- germ × (1 − decline)^years
- Loss type
- compounds each year
- Set by
- species, moisture, temp
- Short-lived
- onion, soybean, parsnip
- Long-lived
- tomato, brassicas
- Action below
- ~70% → reseed or replace
- Slow decay
- keep cool & dry
- Privacy
- Runs in your browser; nothing uploaded
Old seed isn't dead seed — but it isn't fresh seed either
Seed is alive, and like anything alive it ages. A lot that germinated 95% the year it was harvested loses a little germination every season in store, faster if it is warm or damp, slower if it is cool and dry. The loss compounds, so a few years in a shed can quietly turn a good lot into one that emerges thin and patchy — leaving gaps you only notice after sowing.
This tool estimates where a stored lot stands — current viability percentage, the years it has aged, its starting germination and a status flag — from a simple decay model. Use it to decide whether to bump up the seed rate, run a germination test, or buy fresh seed. Pair it with the Seed Storage Life, Germination Test and Seed Rate tools to manage your seed stock confidently.
Avoid thin stands
Catch low viability before it leaves gaps.
Adjust the seed rate
Sow more to compensate for dead seed.
Know when to replace
See when a lot has aged past usefulness.
Store smarter
Cool, dry storage keeps germination longer.
Frequently Asked Questions
What is seed viability decay?+
Seed viability decay is the gradual loss of germination capacity as seed ages in storage. Living seed slowly uses up its reserves and accumulates damage, so a lot that germinated 95% fresh may germinate far less after a few years. How fast it falls depends on the species and on how cool and dry the seed is kept.
How is current viability calculated?+
Viability = initial germination × (1 − annual decline)^years. Each year the lot keeps the surviving fraction of the previous year's viability, so the loss compounds. For example 90% germination declining 10% a year is 90 × 0.9² ≈ 73% after two years, and about 59% after four — the curve falls faster the longer it is stored.
What sets the rate of decline?+
Mainly species, seed moisture and storage temperature. Oily seeds and short-lived species (onion, leek, parsnip, soybean) decline fast; cereals and many legumes last longer; tomato and many brassicas are very long-lived. Cool, dry storage slows decline sharply — the classic rule is that each drop in temperature and moisture roughly extends seed life.
What viability is too low to plant?+
Below about 70% germination most seed lots need attention — either raise the seed rate to compensate for the dead seed, or replace the lot. Certified-seed standards for many crops sit around 70–85% minimum germination. Very low viability also tends to give weak, uneven seedlings, not just fewer of them.
How do I adjust the seed rate for low viability?+
Divide your target plant population by the viability fraction (and by emergence/field-establishment losses). If you need a stand that 80% viable seed would give but your lot is only 60% viable, you sow roughly 80 ÷ 60 ≈ 1.33 times as much seed. The Seed Rate calculator does this adjustment for you.
How can I slow seed decay in storage?+
Keep seed cool and dry — low moisture content and low temperature are the two big levers. Dry seed well before storage, use sealed containers with a desiccant for long-term keeping, and store away from heat and humidity. The drier and cooler the store, the slower viability falls.
Should I run a germination test instead of estimating?+
A germination test is the gold standard — it tells you the actual current germination of your lot rather than a model estimate. Use this decay calculator to anticipate roughly where a lot stands and whether it is worth testing, then run a quick rag-doll or tray germination test before committing the seed to the field.
Does decay affect seedling vigour too, not just germination?+
Yes. Vigour usually declines before germination percentage does, so an aging lot may still germinate reasonably in a lab test but emerge slowly and unevenly in cold or crusted soil. Treat a marginal lot cautiously: even if the germination number looks acceptable, expect weaker field performance.
Are the figures exact?+
They're a planning model. Real decay isn't perfectly constant year to year, and storage conditions vary, so the true viability of a specific lot can differ. Use the estimate to decide whether to test or replace seed, and confirm with an actual germination test before sowing.