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Seed Storage Lab

Seed counts per ounce and pound, and how long orthodox seed keeps at a given temperature and moisture

Rules-of-thumb projections for orthodox seed. Not a test of your seed, and not a germination result. It applies published seed-count tables and Harrington's storage rules to estimate how long dry-stored orthodox seed stays viable. It does not know your seed lot and cannot tell you whether a specific packet will germinate. Only a germination test can. Use at your own risk. Open for the full scope limits.

Model scope

This calculator applies published seed-count tables and Harrington's storage rules of thumb. It estimates how long orthodox seed stays viable under dry storage. It does not test your seed, does not know your seed lot, and cannot tell you whether a specific packet will germinate.

A projection is not a measurement

  • Storage-life figures are projections from thumb-rules, fitted across species and conditions. They describe a tendency, not your packet.
  • The only way to know whether seed is still good is a germination test: 20 to 100 seeds on damp paper towel at the species' optimum temperature.
  • Starting viability matters more than storage time and is invisible here. Seed harvested immature, dried too fast, or damaged in threshing begins below par, and the model assumes it did not.
  • Harrington's rules assume steady conditions. Real storage cycles in temperature and humidity, and cycling is worse than a steady average at the same mean.
  • Nothing here models disease, insect damage, rodents, or a container that was not actually airtight.

Recalcitrant and intermediate species are refused

Refused by design, because dry-storage models do not apply to them. A refusal is an answer, and the right response is to look up the storage behaviour of that species rather than to find a tool that will return a number.

Never use this for

  • Deciding a seed lot is viable, or that it is not, without testing it.
  • Seed bank accession, deaccession or regeneration scheduling.
  • Commercial seed sale, labelling, certification or a germination claim, all of which are regulated and require assay data.
  • Planting or crop planning where a failed stand is expensive or a season is lost.
  • Anything about a species whose storage behaviour is not orthodox.

Verify independently

Check the cited sources and run a germination test before relying on any result for a planting, a seed bank, or a commercial decision. A test on the actual lot settles the question; nothing on this page does.

No warranty. No liability. No suitability claim. You assume all risk. Provided as-is and as-available, without warranty of accuracy, completeness, merchantability, fitness for a particular purpose, agricultural suitability, regulatory acceptability, or commercial value. To the maximum extent permitted by law, the author accepts no liability for any loss, damage, cost or claim arising from use of or reliance on this page, and the author and maintainers disclaim responsibility for crop failure, germination loss, seed-bank decisions, commercial losses, or any other consequence arising from use or misuse of this page.

Independent verification required. Check every figure against the cited sources and against a germination test on the actual lot before acting on it. The test and qualified agronomic judgement control; where this page disagrees with them, this page is wrong.

Consequential damages excluded. To the maximum extent permitted by law, in no event will the author or maintainers be liable for any direct, indirect, incidental, special, exemplary, punitive or consequential damages, including crop failure, lost seasons, germination loss, seed-bank decisions, regulatory exposure, or loss of use, data, profits or business interruption, however caused and on any theory of liability, whether in contract, strict liability or tort including negligence, arising out of or in connection with this page, even if advised of the possibility of such damage.

Indemnity. By using this page you agree to indemnify and hold harmless the author and maintainers against any claim, demand, loss or expense arising out of your use of it or of anything derived from it.

Severability. If any part of this notice is held unenforceable, the remainder continues to apply, and the unenforceable part is limited to the least extent necessary rather than struck out.

Inputs

Pick a species by common name, or work from seeds you counted yourself.

Settings auto-save to this browser as you type.

Ready.
How To Use This Tool

This tool answers three separate questions. Mixing them up is the usual source of confusion.

  • How many seeds are in this packet? Search the species, read the seeds-per-ounce card. If two sources disagree the tool shows both and does not average them: averaging a transcription error with a correct value produces a number that is wrong and looks authoritative.
  • How many seeds do I actually have? Weigh a sample, count it, and enter both under Count. A measured count beats every table here. Published counts carry cultivar, seed-lot and cleaning-standard variation; your own packet has none of that. The published range then becomes a cross-check.
  • How long will this seed keep? Set the storage temperature and moisture. The multiplier is relative to the baseline conditions the published longevity figure is assumed to describe, so the baseline is an editable input.

Moisture content and relative humidity are different quantities. Seed moisture content is water as a percentage of seed weight, typically 5 to 14% in stored seed. Relative humidity describes the air around the seed. Harrington's moisture rule uses moisture content; the Hundred Rule uses relative humidity. Both therefore appear as inputs.

Freezer storage is outside these rules. Harrington's thumb-rules are only valid between 0 and 40 °C. Ask for -18 °C and the tool clamps to 0 °C and says so. Genebank conditions need the Ellis-Roberts viability equation, which this version does not include.

The tool will refuse some species. Acorns, chestnuts, avocado and mango have recalcitrant seed that dies on drying; garlic and potatoes are not grown from stored seed at all. In both cases the tool withholds the storage-life model and explains why. Seed counts still display.

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