Autoflower vs Photoperiod Cannabis
Photoperiod cannabis flowers when the nights grow long, and autoflowering cannabis flowers on its own a few weeks after it sprouts, because it carries genes from a hardy wild relative called Cannabis ruderalis. For top-shelf flower we would still choose photoperiod, mainly because a great photoperiod plant can be cloned and kept for years and an autoflower cannot. Autoflowers win for home growers with short summers and small spaces.
By Eleanore Editorial, editors of the eleanore guides to cannabis craft · Published
Most buyers will never be told which kind of plant they are smoking. The label gives a name and a potency figure, and on a good day a farm. It almost never says whether the plant waited for autumn or simply decided, at about four weeks old, that it was time.
That second kind is far more common than it was.
The pages that rank for this question are written for growers, and they are good at what they do. They compare yields per square metre, light schedules, how many weeks you will wait, which seed bank sells the fastest line. Useful if you own a tent. If you own a jar, the question is narrower and, we think, more interesting. It is whether the way a plant decides to flower changes what ends up in your hand, and whether it should change what you buy.
How each plant knows when to bloom
Cannabis, left to its own devices, reads the calendar through its leaves. Through the summer it grows. When the nights stretch toward twelve hours of uninterrupted dark, the plant takes that as notice that winter is coming and puts everything it has into flowers. Growers call these plants photoperiod, and indoors they fake the season by moving a timer from eighteen hours of light to twelve. Outdoors the sun does it for them, which is why the harvest in Humboldt and Mendocino lands in October and so often races the first rains.
Autoflowers skip the calendar. Their flowering trait comes from Cannabis ruderalis, a scrubby, short-season type first described by the Russian botanist D. E. Janischewsky in 1924, from plants growing wild where summers are too brief to wait for long nights. Breed that trait into a modern cultivar and you get a plant that flowers by age. Put it under twenty hours of light or eighteen or a cloudy balcony in Vancouver and it will bloom on schedule anyway, and most finish somewhere around ten to twelve weeks from the day the seed cracked.
The first autoflower most growers heard of was Lowryder, released in the early 2000s by a breeder working as the Joint Doctor. It was famously short and, by most accounts, not very strong. Breeders spent the next twenty years crossing autoflowering lines back into popular photoperiod cultivars, and the potency gap has mostly closed. Modern autos can test in the same range as plenty of the photoperiod jars beside them, which is one more reason to read our guide on whether THC percentage matters before letting that number settle anything.
The difference that reaches the jar
Here we part company with the grow forums. For a buyer, the gap that matters between these two plants is memory.
A great photoperiod plant can be kept. Take a cutting, root it, keep a mother plant alive in a corner of the room, and that exact plant can be grown again next month and next decade. This is how keeper cuts survive, and our guide to cannabis phenotypes explains why connoisseurs ask whose cut a jar came from. Gorilla Glue #4 was a single selection. Every true jar of it since descends from that one plant.
An autoflower cannot do this, at least not usefully. A cutting carries its parent’s age. Root it and it starts flowering almost at once, as a plant the size of a houseplant, which defeats the point. So every autoflower crop starts again from seed, and seeds scatter. If a grower finds the most beautiful autoflower they have ever smelled, they can try to breed toward it. They cannot keep it.
That one fact explains why you rarely hear of a celebrated autoflower cultivar, and why we would be cautious about paying top-shelf prices for one. The jar might be lovely. The next batch, under the same name from the same farm, is a new draw.
The three ways a jar starts
Read this table from a buyer’s side of the counter. The middle row is the one most often left out, and it matters, because photoperiod from seed carries the same scatter as an autoflower until somebody does the work of choosing.
| Plant | What starts flowering | Time to harvest | Can it be kept as a cut? | Batch to batch | Best for | Key trade-off |
|---|---|---|---|---|---|---|
| Autoflower | Age. Flowers a few weeks after sprouting, whatever the light | Often 10 to 12 weeks | No. A cutting keeps the parent’s clock and flowers tiny | Varies run to run, because every crop starts from seed | Home growers with short summers or small spaces | Nothing exceptional can be preserved |
| Photoperiod, from seed | Long nights (about 12 hours of darkness) | Roughly 3 to 6 months from seed, longer outdoors | Yes, if someone takes a cutting | Varies plant to plant within a pack | Phenohunts and outdoor full-season crops | Slow, and a pack of seeds is a lottery |
| Photoperiod, from a keeper cut | Long nights, set by the grower’s timer indoors | About 3 months from a rooted cutting, 8 to 10 weeks of it in flower | Yes. This is how famous cuts survive for decades | Highest. Same genetics every harvest | Top-shelf flower and repeatable house cultivars | A mother plant takes up room and needs tending every week |
Timings are typical ranges, and a fast indoor photoperiod can finish sooner than a slow autoflower. The column we would read first is the fourth one.
Where each one fits (and where it does not)
Autoflowers are the better plant for most people growing at home, and we would say so to a friend. They stay small. They do not care about a neighbour’s porch light. In a place with a short summer, such as Maine or Michigan’s Upper Peninsula, an autoflower sown in May can be hanging to dry by August, long before the damp nights that rot a late photoperiod crop from the inside. Some outdoor growers in warmer places fit two or even three autoflower harvests into one season. For a balcony and a little patience, nothing else comes close.
Photoperiod plants take longer and ask a great deal more of the grower. They are also the only kind a craft grower can hunt through, select and keep, and that is the whole craft. A photoperiod grown from a random pack of seeds has no advantage over a good autoflower. A photoperiod grown from a cut someone chose out of two hundred seedlings and has kept alive since has an advantage nothing else can buy, and it is the plant behind most of the jars we would call genuinely great.
Sun-grown farms sit in a slightly different place. They grow photoperiod plants in the ground and let the real season do the flipping, and our pages on sun-grown cannabis and indoor vs outdoor cannabis cover what that costs and what it gives back.
On the word automatic
Every plant decides when to flower; the autoflower just stopped asking the sky.
What to ask at the counter
One question does most of the work. Was this grown from seed or from a clone? If the answer is a clone, ask whose cut, and enjoy the conversation. If the answer is seed, ask whether it was autoflower, and then judge the jar on its own nose and its packaging date, the way our guide to what top shelf cannabis means suggests for every jar. Plenty of shops will not know. That is information too.
For pre-rolls the question is harder to answer and matters less, since a pre-roll should be judged on how it burns and how it tastes in the first three draws. Our guide on how to judge a pre-roll covers exactly that. If what you are really choosing is an evening rather than a genetic lineage, that is the question the three Parlor Smokes in The Parlor collection were named for: The Fainting Couch, The Fig Tree and Afternoon Ruse. You can see the rest of the house, including Eleanore Aperitif, in the complete Eleanore collection.
Our position
We have nothing against autoflowers and would happily grow one on a sunny step. On a top shelf, though, we want the plant somebody chose, kept and grew again, because that is the only kind of cannabis that can promise you next season what it gave you this one. Good autoflowers are real. They are also, every time, a first meeting.
Frequently asked questions
What is the difference between autoflower and photoperiod cannabis?
A photoperiod plant flowers when its nights grow long, roughly twelve hours of darkness, which indoor growers imitate by switching their lights. An autoflower carries genes from Cannabis ruderalis and starts flowering on its own after a few weeks, regardless of light, usually finishing ten to twelve weeks from seed.
Is autoflower weed weaker than photoperiod weed?
Not reliably any more. Early autoflowers in the 2000s were small and mild, but modern lines can test in the same range as many photoperiod jars. The bigger difference for a buyer is consistency: an autoflower cannot be kept as a clone, so every harvest is a fresh draw from seed.
Can you clone an autoflower?
Technically you can root a cutting, but it keeps the parent plant’s age clock and flowers almost immediately, producing a very small plant. In practice autoflowers are grown from seed every time, which is why there are no famous autoflower cuts.
How can I tell if the cannabis I bought was autoflower?
Usually you cannot from the flower or the label, since few brands state it. Ask the shop or the brand whether the batch was grown from seed or from a clone, and if a clone, whose cut. A clear answer to the second question means a photoperiod plant.