Autoflowers: The Plant That Ignores the Sun (Science & History)

Watch the episode · 3:52

Most cannabis plants wait for autumn: they only start to flower when the nights grow long. Autoflowers don't wait. They flower on a clock of their own, whatever the light. Here is where that trick came from, and the people who turned it into a revolution.

A clock in the leaves ▶ 0:22

Ordinary cannabis is what botanists call a short-day plant. Its leaves effectively measure the length of the night, and when the nights grow long towards autumn it switches from growing to flowering.

Indoors, growers trigger flowering by cutting the light to 12 hours a day. Until they do, the plant just keeps on growing.

An autoflower ignores all of that. It starts flowering after a few weeks simply because it is old enough. It can grow under the same light from start to finish, and many go from seed to harvest in around 10 to 12 weeks.

The wild ancestor: Cannabis ruderalis ▶ 0:58

The trick comes from Cannabis ruderalis, a hardy wild type described in 1924 by the Russian botanist Janischewsky, growing in southern Siberia.

Where summers are short and unpredictable, a plant that waits for long nights risks being caught by frost before it sets seed. Flowering by age is a survival advantage.

A recessive gene ▶ 1:22

In 2022, researchers at Cornell University mapped one of the main genes behind it, which they named Autoflower1. And it is recessive.

Cross an autoflower with a regular plant and every F1 seed carries one copy of each version, so every one of them still waits for the nights.

Cross those F1s together and the trait reappears, in about one plant in four. It is the F2 lottery from episode 2 on seed pack codes, and it is why breeding a new autoflower takes extra generations.

The exact gene, and the single "typo" in it, was tracked down later: that story is told in episode 15, the autoflower gene.

The milestones ▶ 1:57

For decades ruderalis was a botanical curiosity: small, weedy and low in potency. Then in 2003 a breeder known as the Joint Doctor released Lowryder, bred from a Mexican ruderalis, Northern Lights #2 and William's Wonder. It was the first stable autoflower to go mainstream.

Dutch Passion, the company that pioneered feminised seeds, teamed up with the Joint Doctor and brought the two ideas together, with feminised autoflowers such as Auto Mazar and Think Different.

Early autos were quick and compact, but light on yield. That changed in 2012, when Spain's Buddha Seeds released Magnum, one of the first so-called XXL autoflowers, bred for big, branching plants and heavy harvests. It showed that autos could be productive, not just fast.

From a wild Siberian weed, to Lowryder, to Magnum: in less than a decade, autoflowers went from novelty to mainstream.

The trade-offs ▶ 3:02

Autoflowers are fast, compact and easy to time. But they can't be paused, so there is no extra growing time to recover from a mistake. (The five most common autoflower mistakes all come from that.)

And cloning them makes little sense, because a cutting is the same age as its mother. It starts flowering almost straight away, while it is still tiny.

Regular plants flower when the nights grow long. Autoflowers flower by age, a gift from wild ruderalis. The main gene behind it is recessive, and Lowryder, Dutch Passion's feminised autos and Magnum turned it into a revolution.