How to Test Old Seeds for Germination
By Paul Smith, pemdasgarden.com
Quick Answer: Test old seeds before planting season: place 20 to 50 seeds on a damp paper towel, keep them warm and moist, and count how many sprout. If 70 percent or more germinate, the seed is still good to plant; below that, sow thicker or replace it. A germination tracker logs each test and gives you an automatic pass-or-fail verdict.
Try our free Germination Tracker — log your germination tests and get an automatic pass-or-fail verdict against a 70 percent viability threshold.
Why Test Before You Plant
Seed viability drops over time, especially in heat and humidity. Planting dead or weak seed wastes weeks of the season: you wait, nothing emerges, and by the time you re-sow the window may be gone. A simple test takes a few days and tells you the truth about every packet.
How to Use the Tool
- Set up the test. Moisten a paper towel, place 20 to 50 seeds of one variety on it, fold it over, and slide it into a plastic bag left slightly open.
- Keep it warm. Most seeds germinate fastest between 65 and 75°F. A warm room or the top of a refrigerator works well.
- Check daily. Keep the towel damp, not soggy. Count sprouts after the typical germination window for that crop (7 to 14 days for many vegetables).
- Log your results. Enter the seeds tested and the number sprouted into the Germination Tracker.
- Read the verdict. The tool compares your rate against the 70 percent threshold: pass means plant normally, fail means sow thicker or buy fresh seed.
Practical Tips
- Test 20 seeds minimum for a meaningful percentage — 10 seeds gives too coarse a picture.
- Label everything. Variety and test date on each bag prevent mix-ups when you run several tests at once.
- Don’t throw out borderline seed. A 60 percent rate still grows plants if you sow about 1.5 times as thick and thin later.
Frequently Asked Questions
How long do vegetable seeds stay viable?
Stored cool and dry, many vegetable seeds last 2 to 5 years; onion and parsnip are notably short-lived at about 1 to 2 years, while tomato and cucumber often last 5 or more. Test anything older than a year before trusting it.
What counts as a sprouted seed?
A seed with a healthy root emerging, and for most vegetables a normal-looking sprout. Moldy or stalled seeds do not count.
Can I plant the sprouted seeds from the test?
You can carefully transplant strong sprouts, but they are delicate. Most gardeners use the test as information and sow fresh seed from the packet.
What if only half my seeds germinate?
You have two good options: sow twice as thick and thin the extras, or replace the packet with fresh seed — especially for crops where even spacing matters.
Test your seed stash today — try the free Germination Tracker and know exactly which packets to trust.
Stock Up on Seeds
Replacing tired seed? Browse our vegetable seed collection or flower seeds.
