Diagnosing a Seed That Won't Germinate: The 6-Check Method

Diagnosing a Seed That Won't Germinate: The 6-Check Method

Facing a sowing that won't come up, don't panic — a methodical diagnosis identifies the cause in minutes. Here are the 6 checks to review, from the seed itself to the sowing conditions, according to established gardening practice.

Contents

• 1 — The viability test
• 2 — Examining the sown seeds
• 3 — Substrate temperature
• 4 — Moisture state
• 5 — Depth and oxygen
• 6 — The elapsed delay
• Symptom table
• Frequently asked questions

1 — The viability test: is the seed alive?

First reflex: test a sample from the same batch. Place 10 seeds on moistened absorbent paper in a half-closed bag, at 20-24 °C, and watch:

• 8 seeds out of 10 swell and deform (the radicle expands) → 80% germination expected: the batch is good, the problem is in the conditions.
• Fewer than half respond → consider replacing the batch, or sow much denser to compensate.
• No emergence a week after the normal delay on the packet → replace the seeds.

2 — Examining the sown seeds

Gently dig up a few seeds from the failed sowing:

• Soft, browned or rotten → damping-off or excess water + cold.
• Hard and intact for a long time → dormancy (impermeable coat, need for cold).
• Dry → the substrate dried out during emergence.

3 — Substrate temperature

• Below ~18 °C → warmth-loving seeds rot rather than germinate; pepper and aubergine refuse to emerge below 18 °C.
• In open ground below 7 °C → no germination; wait for warmer soil and the end of frost.
• Above 25-30 °C → cool species (spinach, lettuce) refuse to emerge.
• Quick diagnosis: a thermometer or heat mat reveals and fixes the problem in one go.

4 — Moisture state

• Soggy substrate (water drips when squeezed) → rot and suffocation of seeds.
• Dry substrate (crumbles to powder) → imbibition never started.
• Wet-dry-wet cycle → the sprouting germ withered during the dry phase.
• Target: evenly moist, never soggy.

5 — Depth and oxygen

• Correct depth: 2-3 times the seed's diameter. Too deep = lack of oxygen.
• Compacted or saturated substrate → seeds lack air.
• Prolonged soaking (>24-48 h without rinsing) → suffocation.

6 — The elapsed delay

Last check before condemning the sowing: has the species' normal time passed? Radish emerges in 2-4 days, celery in 3 weeks, parsley in a month. Most annuals: 3-10 days. No emergence a week after the delay on the packet = negative verdict.

Symptom table

Frequently asked questions

How to know if a seed is dead?

The 10-seed test on moist paper kept warm: swollen and deformed = alive; intact after double the normal delay = probably dead or deeply dormant.

Why do seeds emerge then die?

That is damping-off: fungi kill the seedling at the collar. Proven prevention: sterile substrate, disinfected containers, sparse sowing, bottom watering, lid removed at emergence.

Can I re-sow in the same spot?

Yes, after correcting the cause: temperature raised, excess water removed, fresh sterile substrate — and seeds tested alive.

To eliminate the variables in one go, the Germie germination kit starts on sound bases: sterile pots, adapted substrate, controlled moisture.

Want your home sowings to succeed? Germie's reusable germination kits get your seeds started in record time — and the Gardiscan analyses your soil for a perfectly calibrated start.