Short answer
No. A floating cannabis seed is not necessarily dead; the float test mostly measures trapped air, and many floaters sink within hours and sprout normally. Judge seeds with a 7-day germination test instead. Myth.
Why
A dry seed carries air in and around its shell. Until water gets in, that air can keep a perfectly viable seed on the surface.
Hydration, not viability, decides when it sinks. Seeds take up water over several hours, which is why a 12–24 hour soak is used to speed germination [3]. A floater on hour one often sinks by hour six.
Viability is measured by germinating seeds. Seed laboratories test hemp by putting seeds in a germinator for 7–14 days and counting sprouts [4]; the simple home version is 10 seeds on a damp towel.
What really kills seeds is storage. Warm, moist storage costs germination capacity, while cold, dry storage at about 5 °C (41 °F) kept it for around six years [2]. Old, slow seed may still be pushed with a 1% hydrogen peroxide protocol [1].
The numbers
| Check | Reliable? | Notes |
|---|---|---|
| Float test | No | Mostly measures trapped air |
| Colour and hardness | Rough guide | Varies by genetics |
| 10-seed towel test | Yes | 22–26 °C (72–79 °F), dark, 7 days |
| Lab germination test | Yes | 7–14 days in a germinator |
| Soak length | ≤ 24 h | Longer risks oxygen starvation |
What to do
- Ignore floating; plant or towel the seed anyway.
- If a seed floats after 12 hours, tap it under gently, then move on at 24 hours.
- For a big or old batch, run a 10-seed test first.
- Store the rest cold, dry and airtight.
Common mistakes
- Binning floaters from a precious pack.
- Soaking for days waiting for a seed to sink.
- Squeezing seeds to "test" them and cracking good ones.
Related
- Full article: Germination methods compared
- Seed viability and storage · Seed germination testing
- Why won't my seeds germinate?
- Terms: seed coat · germination
