Quick answer: test a sample and keep the counts
Place a counted sample on moist paper towel, provide the crop's germination conditions and record how many seeds sprout. Germination percentage = seeds germinated ÷ seeds tested × 100. Keep the result with the packet identity, test dates and conditions so it can inform your next sowing.
This is a home planning check, not a certified seed test or a guarantee of plants outdoors. Copy the worksheet below into a notebook or spreadsheet; this page does not save entries. Use one record per seed lot, even when two packets contain the same variety.
Plan the test before the sowing deadline
Prioritise older packets, seed with uncertain storage history and batches needed for an important sowing. Allow time for the crop's full germination period, a possible repeat and replacement delivery. Iowa State University Extension suggests checking stored seed about a month before planting and randomly selecting at least 20 seeds when stock permits.
For a scarce packet, record a smaller sample explicitly or make an early trial sowing in modules. Ten seeds give only ten-percentage-point steps; twenty give five-point steps. Neither sample can establish the exact performance of the remaining packet. Do not select only the largest or best-looking seeds and then treat the result as representative of unsorted stock.
Read the packet before setting up. Record its temperature, light, timing and any pretreatment instructions. University of Illinois Extension notes that some flowers need cold, moist stratification; a simple warm test without that treatment can be misleading. Seek species-specific instructions when the packet is missing.
Run a labelled paper-towel test
- Identify the sample. Label a clean bag with the packet or lot ID, crop, variety, start date and seed count. Keep different lots separate.
- Prepare the towel. Moisten clean paper towel, drain excess water and space the counted seeds apart. For seed suited to a covered test, fold or roll the towel around them.
- Keep it moist with air available. Put the towel in a plastic bag with small ventilation holes, following the University of Maryland Extension method. Check moisture during the test; the seeds should not sit in pooled water.
- Match the crop's conditions. Use its recommended temperature and light exposure. Light-requiring seed needs an arrangement that exposes it to light rather than an opaque folded covering. Record the actual location and measured temperature if available; avoid guessing that a windowsill or radiator provides suitable conditions.
- Check daily and log new sprouts. For this home record, count a seed once when a root emerges through its coat. A swollen seed alone is not a sprout. Mark its position or remove it after counting so it cannot enter tomorrow's count again.
- Close the test deliberately. Use the crop's expected germination period and note the last new sprout and final check date. Do not declare every crop a failure after seven days. Record drying, excess heat or other interruptions alongside the result.
A towel makes individual sprouts easy to see. A labelled module trial instead records emergence through growing medium and may fit scarce seed you intend to grow on. Keep the method in the record: emergence and towel sprouting are different observations, so do not silently combine their counts.
Copy this seed test record
Complete the setup fields first. Leave results blank until observed; “not tested” is different from zero germination.
- Batch identity
- Test ID: ______; packet ID: ______; crop and variety: ______; supplier or saved-seed source: ______; lot number: ______.
- Seed history
- Purchase or harvest year: ______; printed sow-by date: ______; storage location and known problems: ______. Mark unknown information as unknown.
- Setup
- Start date: ______; seeds tested: ______; sampling method: ______; towel or module method: ______; pretreatment and dates: ______.
- Conditions
- Instruction source: ______; target temperature and light: ______; actual conditions: ______; expected germination window: ______; planned final check: ______.
- Final result
- Final check date: ______; cumulative sprouts: ______ of ______ tested; germination: ______%; weak or damaged growth notes: ______; test problems: ______.
- Decision
- Use, retest or replace: ______; reason: ______; action deadline: ______; remaining packet quantity after testing: ______.
| Check date | New sprouts | Total sprouts so far | Conditions and actions |
|---|---|---|---|
| ________ | ________ | ________ | Moisture, temperature, mould, removals: ________ |
Add only new sprouts to the running total. Keep the original number tested as the denominator, including seeds that rot or are removed without sprouting. If seeds are lost or counts become uncertain, flag the test as unreliable and repeat it rather than improving the percentage by deleting failures.
Worked example: 16 sprouts from 20 seeds
This invented record shows the arithmetic, not a crop-specific germination timetable. Suppose successive checks record 6, 7 and 3 new sprouts, with none thereafter during the appropriate test period. The cumulative count is 6 + 7 + 3 = 16, so 16 ÷ 20 × 100 = 80%.
If you choose to use that result as a planning assumption for 24 newly germinated seedlings, calculate 24 ÷ 0.8 = 30 seeds. This is an estimate before losses after germination, not a promise of 24 usable transplants. Choose and record any additional allowance separately, then check capacity in your seed-starting plan. Do not calculate a sowing quantity by dividing by zero after a failed test.
If the packet contained 100 seeds before the 20-seed test, 80 remain as dry stock. A subsequent 30-seed sowing leaves 50. Any test seedlings you keep belong in a separate seedling count; they do not go back into the dry-seed inventory.
Decide whether to use, retest or replace
| Observation | Planning action |
|---|---|
| Enough sprouts for your plan; conditions stayed suitable | Use the batch with its dated result and allow for later losses. Check actual emergence after sowing. |
| Some sprouting, but too few for a dependable sowing | Compare extra seed and propagation space with the cost and arrival time of replacement seed. Keep a valuable scarce batch as a separate trial. |
| No sprouts or an unexpectedly poor result | Check instructions, duration and conditions. Retest a fresh sample if time allows; arrange replacement for a sowing you cannot delay. |
| Towel dried out, conditions were wrong or counts are uncertain | Mark the test compromised. Preserve the observations and create a new test ID rather than overwriting them. |
There is no single home-garden pass mark that suits every crop and sowing. Record what you need from this batch and why you accept it. A small sample with every seed sprouting still does not prove the whole packet will do so.
Keep weak or malformed growth visible in the notes even after a seed has entered the sprout count. Iowa State's Seed Laboratory evaluates normal seedlings under controlled, species-specific conditions in its standard germination test. The root-emergence count used here is a simpler observation and should not be labelled a laboratory germination certificate.
Mould or decay warrants a note, not an automatic diagnosis of the entire packet. If contamination obscures the result, repeat with clean materials and suitable moisture. A towel result also cannot reproduce the soil, weather and pest pressures of outdoor establishment.
Update the packet and next sowing
Write the test date, count and decision on the packet or an attached label. Link the full record from your seed inventory, subtract all seeds used in the test and add any replacement to the purchase list. Keep the original record when repeating a test so changes in method remain visible.
Return unused dry seed to cool, dry storage in a labelled, tightly sealed container, as advised by University of Minnesota Extension. Follow any special packet storage instructions. Keep wetted test seeds separate from stored stock.
Healthy test sprouts can sometimes be grown on if the crop and timing suit; handle fragile roots carefully. Keep them labelled as a test batch. Follow treatment-label handling and disposal instructions for treated seed, and do not use garden test sprouts as food.
At the next sowing, record seeds sown and actual emergence in your garden journal. Review older results before relying on the packet in a later season, especially after a storage problem. A dated test is evidence from that sample and occasion, not a permanent quality rating.
Sources and review
Reviewed by Grow Blueprint on 23 September 2026. The record fields, decision table and numerical example are original planning aids. Use packet or species-specific guidance for test conditions and duration.
- Iowa State University Extension: How to Store Seeds and Test Germination Rates — sampling, timing and sprout checks.
- University of Maryland Extension: Poor Germination of Vegetable Seeds — ventilated towel tests and crop-dependent conditions.
- University of Illinois Extension: Are my seeds still good? — packet guidance and stratification cautions.
- Iowa State University Seed Laboratory: Standard Germination Test — distinction from controlled normal-seedling assessment.
- University of Minnesota Extension: Saving vegetable seeds — storage and labelling.