Why Didn't Your Seeds Sprout? (6 Reasons)

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You planted five seeds. Only two came up. What happened to the rest? It's usually not bad luck. What a failed seed looks like tells you why it failed: still hard, soft and mushy, or cracked open and then dead. There are six reasons, all from the research, and one fix scientists use in the lab improved germination by more than a third.

Still hard: it never cracked ▶ 0:23

First, the seed that never even cracked. It's still hard and unchanged. Reason one is age. A 2025 study reports that some commercial hemp seed lots lost half their germination after just one year of storage.

Warm, damp storage speeds that loss up. The researchers' advice: keep seed moisture under 8%, and store seeds at 4 to 10 °C. Sealed, in the fridge, is ideal. (More on that in how long cannabis seeds last.)

Source · Cockson et al., Agrosyst. Geosci. Environ. (2025)

Reason two: the seed was never ripe. Small, pale seeds are often immature. In a hemp study, ripe seeds sprouted 85% of the time, unripe ones only 15%.

Source · Yilmaz et al., TURJAF (2025)

Reason three: it was too cold. A hemp study measured germination from 3 to 42 °C. Below about 3.5 °C, nothing happens. It's fastest near 30 °C, and it stops again above about 42 °C. The sweet spot is roughly 19 to 30 °C. A cold windowsill isn't a death sentence, just a very slow lane.

Source · Geneve et al., Crops (2022)

So how long should you wait before giving up? Working from that study's numbers, half the seeds sprout after about 700 degree-hours above the base temperature. At 25 °C, that's around 32 hours. On a 10 °C windowsill, it's about four and a half days. If it's cold, be patient.

Reason four: the shell itself. In weak seed lots, a lab team carefully removed the outer shell, and germination improved by about 38%. That's the lab fix. But don't peel your seeds at home: it's delicate lab work, and healthy seeds need that shell. And wearing the shell down so water gets in? A 2025 hemp trial tried it with acid, and it didn't significantly help.

Source · Tan et al., Crops (2022); HortTechnology (2025)

Soft and mushy ▶ 2:01

If your seed went soft and mushy, reason five applies: it drowned. A waking seed breathes hard, and oxygen moves through water about 10,000 times more slowly than through air. As covered in the best way to germinate seeds, a short soak is fine; days underwater are not.

Source · Voesenek et al., New Phytol. (2006)

And a drowning seed is easy prey. Cold, wet soil is where water moulds like Pythium thrive. They rot the seed before it ever shows a root. Soft and mushy usually means too wet.

Source · Oregon State Univ. Extension, hemp seedling diseases

Cracked, then died ▶ 2:33

And if it cracked open, then just died? Reason six: it dried out. Nobody has tested this in cannabis yet, so this is how seeds in general work, from studies in a small lab plant. A dry seed survives drying easily. But once germination is under way, and the root is pushing out, that protection is gone. Let it dry out now, and the tiny root dies.

Source · Maia et al., New Phytol. (2014)

That's why a paper towel that dries out overnight is so deadly. Once a seed has cracked, never let it dry.

The diagnosis ▶ 3:05

So how do you tell which one it was? Still hard and unchanged: old, unripe, too cold, or a stubborn shell. Soft and mushy: drowned, or rotted by water moulds. Cracked, then died: it dried out.

So next time: store your seeds cool, dry and sealed. Keep them warm, about 20 to 30 °C. Moist but not soggy, in a light mix rather than rich fertiliser, because hemp is sensitive to salt as it germinates. And once a seed has cracked, never let it dry out.

Source · Kasprowiak et al., Plants (2025)

Get those four right, and most seeds will come up.

Still hard means old, unripe or cold. Soft and mushy means too wet. Cracked, then died means it dried out. And once your seeds are up, keep the next problem away too: why seedlings stretch.