7 Seed Myths You Still Believe (What the Science Says)

Watch the episode · 4:54

Almost everything you can see on a seed belongs to its mother, not to the plant inside it. And that one fact busts half the seed myths growers swear by. Here are seven of them, what the science actually says, and a verdict on every one. Number seven is the one every grower asks about.

What's really in a seed ▶ 0:27

Botanically, a cannabis seed is a tiny fruit called an achene, just a few millimetres long. Take it apart and there are four layers: a thin, papery skin called the perianth, the hard shell, a thin seed coat, and inside, the embryo, the actual new plant. (There is a full tour in what happens inside a sprouting seed.)

Here is the key. The skin, the shell and the seed coat all grow from the mother plant's own tissue. Only the embryo is new: half from the mother, half from the father. So the outside can tell you whether a seed is ripe, but its stripes and shape come from the mother, not from the plant you will grow.

Myth 1: tiger stripes ▶ 1:02

Myth #1

“Dark tiger stripes mean a strong seed”

Myth

Stripes = mum's skin, not seed quality

McPartland & Small, PhytoKeys (2020)

Dark tiger stripes mean a strong, healthy seed? Those stripes are the perianth, the mother's papery skin. In wild-type cannabis it stays on as speckled camouflage, while many domesticated seeds shed most of it. So stripes tell you about ancestry, not quality.

Myth 2: pale seeds ▶ 1:23

Myth #2

“Pale seeds just need more time”

Myth

Pale and soft usually means unripe

Pale, green or white seeds just need a little longer to sprout? A pale, soft seed is usually unripe, and unripe seeds rarely make it.

In a 2025 hemp study, fully ripe seeds germinated 85% of the time and unripe seeds 15%. In soil it was 83% against 13%, and the survivors grew shorter roots. Plant the hard, dark, fully formed ones.

Myth 3: the float test ▶ 1:58

Myth #3

“Seeds that sink are the good ones”

Myth

Floating = air, not a dead seed

Bonner & Gammage, Tree Planters' Notes (1967)

Drop your seeds in water, keep the sinkers and bin the floaters? Whether a seed floats depends mostly on trapped air and how dry it is. Forestry scientists found float tests work for some acorns but fail for other species, and dry, healthy seeds can float. Nobody has shown it works for cannabis. Seed labs don't use it; they run germination tests.

Myth 4: bigger seeds ▶ 2:26

Myth #4

“Bigger seeds grow bigger plants”

Half True

A head start, not a destiny

Mi et al., Agriculture (2020)

Bigger seeds grow bigger plants? Half true. A bigger seed packs more food for the seedling, so it gets a head start. In a Cornell trial the largest hemp seeds gave up to a third more young leaf weight than unsorted seed. But the variety, and how well the seeds germinated, mattered more than size. The follow-up episode, do bigger seeds grow bigger plants?, digs into whether that head start lasts.

Myth 5: feminised = GMO ▶ 2:54

Myth #5

“Feminised seeds are GMO”

Myth

No genes edited: a female makes pollen

Lubell & Brand, HortTechnology (2018)

Feminised seeds are genetically modified? No genes are edited. Breeders spray a female plant with silver thiosulfate, which makes her grow male flowers. That pollen can only pass on an X, so the seeds come out female. It is chemistry on the flower, not a change to the DNA: episode 1 shows the whole process.

Myth 6: old seeds ▶ 3:18

Myth #6

“Old seeds are dead seeds”

Half True

Storage decides, not the calendar

Small & Brookes, J. Natural Fibers (2012)

Old seeds are dead seeds? Half true, because storage decides. In a hemp study, seeds kept at room temperature at about 11% moisture had all stopped germinating within 18 months; kept cool and dry, they lasted far longer. Episode 5 has the full storage guide.

Myth 7: spot the female ▶ 3:46

You can spot a female seed by its shape, size or stripes? Remember: the outside of a seed is the mother's tissue, so it cannot tell you anything about the embryo inside. A seed's sex is decided in the embryo, by its sex chromosomes: two X's for a female, an X and a Y for a male.

Source · Prentout et al., Genome Research (2020)

Myth #7

“You can spot a female seed”

Myth

Only a DNA test can tell

Riera-Begue et al., Planta (2025)

No look, weight or shape will tell you. The only reliable early test is DNA. In a 2025 study, a test on seedling leaves matched the plants' real sex in all 600 samples, weeks before any flowers appeared.

Source · Riera-Begue et al., Planta (2025)

The final score ▶ 4:24

Five myths and two half-truths. The big idea to take away: almost everything you can see on a seed comes from its mother. What matters is what is inside.