Are Triploid Seeds Worth It? (What the Research Shows)

Watch the episode · 4:34

This seed has three copies of every chromosome, and that is why it hardly makes seeds. Triploid seeds are one of the newest seed types around, with a simple promise: flowers that stay seedless, even when stray pollen blows in. Researchers tested that promise in fields across three US states. It works, but with a catch most growers don't expect.

Three sets ▶ 0:28

Normal cannabis is diploid. Its cells carry two sets of ten chromosomes, one set from the mother and one from the father: think of them as two decks of cards. A triploid has a third deck, so thirty chromosomes in all. It can even happen by accident: a 2023 study found about one natural triploid in every 200 seedlings.

Source · Philbrook et al., Plants (2023)

How they're made ▶ 0:54

Breeders make them in two steps. First they double a plant's chromosomes. A chemical such as colchicine or oryzalin stops a dividing cell from splitting in two, so it keeps both copies: four sets, a tetraploid. Then they cross that tetraploid with a normal plant. Its egg carries two sets, the pollen brings one, and the seed ends up with three.

It is harder than it sounds. In one study the doubling worked on only a quarter to two thirds of the treated seeds, and the first triploid hemp plants, reported in 2020, had to be rescued as embryos and raised in a lab dish.

Source · Kurtz, Brand & Lubell-Brand, HortScience (2020)

One detail matters for growers. Make the cross with pollen from a reversed female and every seed is XXX: female. Use male pollen and some seeds are XXY. In a small 2024 study, still a preprint, six of eight XXY triploids grew both male and female flowers.

Nearly sterile ▶ 1:56

Three sets can't be split evenly in two. To make an egg or a pollen grain, a plant halves its chromosomes, sending one copy of each to each side. With two copies that is easy. With three, one side gets two copies and the other gets one, chromosome by chromosome, at random. Almost every egg ends up with the wrong mix and fails, so when pollen lands on a triploid, very few seeds form.

If that sounds familiar, it should: it is exactly how seedless watermelons work. They were first bred in Japan by Hitoshi Kihara with the same trick: double the chromosomes, then cross back to a normal plant.

Source · Kihara, Proc. Am. Soc. Hortic. Sci. (1951)

The field test ▶ 2:39

Now the real test. Over two seasons, researchers grew two hemp varieties, each in a diploid and a triploid version, in Kentucky, New York and North Carolina. Some fields had pollen blowing through them; others were kept pollen-free.

With pollen around, the triploids made 77 to 87% fewer seeds, and the seeded diploids lost seed-free flower weight and cannabinoids. But in the pollen-free fields there was no real difference in yield or cannabinoids, even though the triploids grew taller and wider.

Worth it? ▶ 3:19

So are they worth it? It all comes down to one thing: pollen.

Claim #1

“Triploids are seedless”

Half True

Far fewer seeds, not zero

Suchoff et al., Agron. J. (2024)

Claim #2

“Triploids yield more”

Half True

Bigger plants, but same yield without pollen

Crawford et al. (2021) · Suchoff et al. (2024)

If pollen can reach your plants, outdoors near hemp fields or other growers, triploids are real insurance. In a sealed indoor grow with feminised seeds, the research shows little to gain. And remember that a triploid is a dead end for breeding: it makes almost no seeds of its own.

Triploids carry three chromosome sets and are made by crossing a tetraploid with a normal plant. Their odd number of sets means far fewer seeds, so they are worth it where pollen can drift in.